The Cerebral Cortex

The cerebral cortex is the convoluted gray matter that forms the outermost layer of the brain. It consists largely of specialized neurons that process and respond to specific sensory stimuli. The cortex receives electrical discharges from other neurons and converts them into ideas or actions. The cortex is divided into five anatomic divisions: the frontal, parietal, temporal, occipital, and limbic divisions.

The cortical neurons are specialized so that within each major division of the brain, specific areas are devoted to specific functions. Fifty-two specialized areas were identified in the late 1800s by Korbinian Brodmann; these areas are numbered according to histologic appearances and functions. If brain injury is identified in one of these areas, it is possible to predict the resulting sensory or functional impairment. Conversely, a lesion often can be localized according to the motor functions or sensations that are impaired. It is important to note, however, that most functions can be performed through impulses from several areas of the brain.

The cerebral cortex performs the highest functions of the human brain. As a result, it continues to develop beyond infancy and childhood. The newborn responds to the environment with simple awareness and reflex behavior. During infancy, individual sensations, sights, and sounds can be stored in memory in the cerebral cortex, and the infant learns to associate these sights and sounds with events or feelings. As the infant develops into a toddler, higher cortical functions such as imagination and language become apparent.

There is tremendous growth of cortical function during the early years of life. Most developmental and neurologic assessment tools evaluate only basic reflexes and motor skills of the young infant and toddler, and it is not until the preschool and the early childhood years that cognitive functions and learning can be evaluated.

The cerebral hemispheres are two mirror image portions of the brain that consist largely of the cerebral cortex and fiber tracts. In general, each cerebral hemisphere governs the functions of and receives sensations from the contralateral side of the body. Therefore, the right cerebral hemisphere governs movement of and receives sensory input from the left side of the body. The left cerebral hemisphere governs movement of and receives sensory input from the right side of the body.

In most humans, one side of the brain is considered dominant; right-handed people are thought to have a dominant left side of the brain, and left-handed people are thought to have a dominant right side of the brain. Each hemisphere also has primary responsibility for some functions. In most people, the left hemisphere controls language and speech, and the right hemisphere helps interpret three-dimensional images and spaces. Other distinctions have been postulated. For example music understanding is thought to be predominantly controlled by the left hemisphere and arithmetic and design are thought to be controlled by the right hemisphere. To a certain extent, if one side of the brain is injured, the other side of the brain can be taught to assume the dominant functions (this compensation is called plasticity). This compensation is more likely when the injury occurs during infancy or early childhood, because cerebral dominance is not established fully until approximately 3 years of age.

The cerebral hemispheres are connected by nerve fibers called the corpus callosum. These nerve fibers allow the brain to function as a single unit despite its division into two hemispheres.

The Basal Ganglia

The basal ganglia are paired masses of gray matter deep within the cerebral hemispheres. They contain the nuclei of neurons and networks of tracts that control motor function. These basal ganglia send information to the motor cortex through the thalamus to inhibit unintentional movement. Thus, the basal ganglia regulate the extrapyramidal motor system. This system selects motor messages from lower pathways for interpretation up to the cerebral cortex; thus it influences motor activities, musculoskeletal control, rhythmic movement, and maintenance of an erect posture.

Interference with neurotransmission to the basal ganglia produces disturbances of intentional movement. The uptake of bilirubin by the brain during infancy, known as kernicterus, affects this area and can result in the development of neurologic dysfunction.

The Thalamus and Hypothalamus

The thalamus surrounds the third ventricle and is composed of tracts of gray matter. The thalamus is a major integrating center for afferent impulses from the body to the cerebral cortex.⁸⁵ The thalamus integrates and modifies messages that come from the basal ganglia and cerebellum and then transmits information up to the cerebral cortex. All sensory impulses, with the exception of those from the olfactory nerve, are received by the thalamus. These impulses are then associated, synthesized, and relayed through thalamocortical tracts to specific cortical areas. The thalamus is the center for the primitive appreciation of pain, temperature, and tactile sensations.

Lying beneath the thalamus and near the optic chiasm is the hypothalamus. It is the chief region for subcortical integration of sympathetic and parasympathetic activities. The hypothalamus secretes hormones that are important in the control of visceral activities, maintenance of water balance and sugar and fat metabolism, regulation of body temperature, and secretion of endocrine glands. The hypothalamus is the source of two hormones: vasopressin (antidiuretic hormone [ADH], also called arginine vasopressin) and oxytocin. These hormones are synthesized by the hypothalamus and are transmitted in nerve tracts to a small mass of tissue suspended below the hypothalamus, called the posterior pituitary gland or neurohypophysis. Vasopressin and oxytocin are then released by the posterior pituitary gland as needed.

The anterior pituitary gland, called the adenohypophysis, secretes hormones that control glands throughout the body; these hormones include growth hormone (somatotrophin), adrenocorticotropic hormone, thyroid-stimulating hormone, melanocyte-stimulating hormone, follicle-stimulating hormone, luteinizing hormone releasing factor, and prolactin.

Injury to or disease of the hypothalamus or the pituitary can produce a wide variety of neuroendocrine problems and can result in fluid and electrolyte imbalance and growth disturbances (see Chapter 12).

Cerebral Blood Flow

Cerebral blood flow (CBF) is the volume of blood that is in transit through the brain over a unit of time (e.g., per minute); this term is commonly used to describe the cerebral arterial flow perfusing the brain. Cerebral blood volume (CBV) is the total amount of blood in the intracranial vault at any one time, and it consists of both arterial and venous blood.

Normal CBF in adults is approximately 60   mL per 100   g brain tissue per minute. The normal quantity of CBF in children is unknown, but is thought to be approximately 50 to 100   mL per 100   g brain tissue per minute or more. The absolute quantity of CBF is not as important as the relationship between cerebral oxygen, substrate delivery, and cerebral metabolic requirements. It is essential that CBF is adequate to maintain effective cerebral oxygenation to sustain cerebral functions. Under normal circumstances, CBF, metabolism, and oxygen extraction are closely interrelated.¹³³

Cerebral Venous Return

Cerebral venous return from superficial and deep cerebral veins flows into venous plexuses and dural sinuses, then into the internal jugular veins. If cerebral arterial flow is maintained in the face of obstructed cerebral venous return, CBV will increase and ICP may rise. Cerebral venous return can be obstructed by compression or thrombosis of the internal jugular vein, or by any condition that obstructs superior vena caval flow (e.g., mechanical ventilation with high inspiratory pressures, the development of a tension pneumothorax, or the Valsalva maneuver). Increased ICP can compress cerebral veins, impeding cerebral venous return. When increased ICP is present, turning the head to one side can obstruct internal jugular venous flow, increase CBV, and worsen ICP.

Autoregulation

CBF normally is maintained at a constant level by cerebral autoregulation, which is the constant adjustment of the tone and resistance in the cerebral arteries in response to local tissue biochemical changes.⁷² Autoregulation is essential to the maintenance of cerebral perfusion and function over a wide variety of clinical conditions. If systemic arterial pressure increases, cerebral arterial constriction will prevent a rise in the cerebral arterial pressure to maintain CBF at a constant level. Conversely, if systemic arterial pressures falls, cerebral vasodilation will minimize the effects on CBF. Severe alterations in systemic arterial blood pressure will exceed the limits of autoregulatory compensation, however, and will be associated with changes in CBF.

Autoregulation may be compromised or destroyed with severe traumatic or anoxic brain injury. If cerebral autoregulation is lost, CBF becomes related passively to the mean arterial pressure (MAP) so that a fall in MAP will result in a decrease in cerebral flow and perfusion. Recent studies suggest that impaired autoregulation in traumatic brain injury may correlate with severity of injury and young age.¹²⁶

Alterations in Cerebral Blood Flow

In some conditions, including head injury and some encephalopathies, CBF (oxygen and substrate delivery) and cerebral metabolic demand may differ. This uncoupling of oxygen delivery and demand can lead to regional ischemia in some portions of the brain or to excessive CBV with subsequent increase in ICP.

CBF can increase with anemia, administration of vasodilators, and hyperthyroidism. It also can increase if the CSF pressure is abnormally low or if a hemangioma or arteriovenous malformation is present.

Seizures (particularly status epilepticus) increase CBF and can increase cerebral metabolic rate. If seizures develop in the patient with increased ICP, the additional CBF can produce a further rise in ICP.

CBF will likely be compromised if CSF pressure or ICP rise. The ultimate complication of an accelerating rise in ICP following head injury is the cessation of CBF, producing brain death. CBF also can decrease in the presence of coma or as a result of a rise in cerebral venous pressure, polycythemia, or hypothyroidism.

If CBF is reduced severely, local cerebral metabolism is compromised, and brain cell metabolic functions will be compromised and may cease. If ischemia continues, brain cell membranes will become more permeable, and water will enter the brain cells. Profound ischemia can result in permanent neurologic dysfunction or brain death.

Effects of Arterial Blood Gases on Cerebral Blood Flow

CBF is affected by significant changes in arterial oxygen and carbon dioxide tensions.

Cerebral Perfusion Pressure

Cerebral perfusion pressure (CPP) is calculated as the difference between the systemic mean arterial pressure (MAP) and the ICP:

The normal range of CPP is thought to be approximately 50 to 150   mm Hg in healthy adults, with a goal of 70   mm Hg following traumatic brain injury. There is a paucity of information to identify the normal range of CPP in children; it is thought to be approximately 40 to 60   mm Hg, but normal ranges vary with age.^9,48 A CPP of at least 40   mm Hg is thought to be necessary for effective cerebral perfusion; however, this number is not absolute because perfusion is determined by blood flow, not blood pressure. It is likely that a CPP of 40   mm Hg is acceptable in an infant, but a CPP of 50 to 65   mm Hg is likely to be necessary in older children and adolescents.

The calculated CPP will fall if the mean systemic arterial pressure falls, if the mean ICP rises, or if both occur simultaneously. The calculated CPP can be maintained despite a rise in ICP if the MAP rises commensurately with a rise in ICP. It is important to note that such compensation may or may not be associated with effective CBF and actual cerebral perfusion (for a Case Study of calculation of CPP, see the Chapter 11 Supplement on the Evolve Website); a normal CPP (40-50   mm Hg or more) has been recorded after brain death was pronounced.¹⁶

A clinical correlate of CPP in patients with increased ICP might be the MAP in patients with cardiovascular dysfunction. Patients with normal CPP may or may not demonstrate effective cerebral perfusion, just as patients with cardiovascular dysfunction and a normal blood pressure may or may not demonstrate effective systemic perfusion. Shock may be present with a normal blood pressure, and cerebral ischemia may be present with a normal calculated CPP. Therefore, the CPP should be calculated and evaluated in light of the patient’s clinical appearance and neurologic function; a low CPP is worrisome, and a high or normal CPP is not reassuring in the presence of intracranial hypertension and clinical, especially neurologic, deterioration.

Evaluation of Cerebral Blood Flow

Qualitative radioisotope scans have been performed for a number of years to determine the presence or absence of CBF. However, quantitative CBF measurements cannot be readily performed at the bedside of the critically ill patient using standard pressure measuring devices. A variety of techniques can detect and monitor trends in CBF.

Increased Brain Volume

An increase in brain volume can result from cerebral edema or cerebral swelling. Cerebral edema is categorized as vasogenic, cytotoxic, osmotic and interstitial; the etiology and treatment of each category of edema may vary.

Vasogenic cerebral edema is characterized by increased cerebral capillary permeability and disruption of the blood brain barrier in the absence of neuronal injury.⁷¹ The increased permeability often is caused by inflammatory conditions such as encephalitis and meningitis. When capillary permeability is increased, proteins leak from the vascular space. Because proteins exert osmotic force, when they move from the intravascular to the extravascular space they pull water from the intravascular to the extravascular space, worsening edema and creating further ischemia and further edema.

Cytotoxic cerebral edema or cellular swelling usually is associated with severe neural cell damage. It occurs across the spectrum of brain injuries, but particularly in traumatic brain injury and ischemic injury. The edema occurs secondary to dysfunction of intracellular mechanisms, which promote sodium and water accumulation in the cells, with resultant cell swelling.^71,108

Osmotic cerebral edema results from an acute fall in serum (and therefore extracellular) osmolality that results in an acute free water shift from the intravascular/extracellular space to the intracellular space. Interstitial cerebral edema results from impaired absorption of CSF.¹⁰⁸ Most commonly, this form of cerebral edema is observed in patients with obstructive hydrocephalus.

Increased Cerebral Blood Volume

Increased CBV can result from increased CBF or obstruction to cerebral venous return. Regional increases in CBF can result from head injury (and activation of inflammatory mediators) and some encephalopathies, and it can also be associated with hypercarbia or significant hypoxemia.

Cerebral venous return may be compromised if the jugular vein is obstructed through clot formation or compression (e.g., turning of the head). Significant elevation in intrathoracic pressure may impede jugular venous return and cerebral venous drainage, so high levels of positive end-expiratory pressure (exceeding 8-10   cm H₂O), should be avoided, if possible, in patients at risk for increased ICP.

Arteriovenous malformations are the most common nontraumatic cause of intracranial hemorrhage in children.⁵⁵ Head trauma also can result in accumulation of blood in the subdural or epidural space, or in an intracerebral hematoma. Intraventricular hemorrhage can occur after a traumatic injury or in premature infants.

Cerebral Spinal Fluid Accumulation

CSF will accumulate if there is an obstruction to CSF flow or a compromise in CSF reabsorption. Obstruction to CSF flow may complicate recovery from meningitis if inflammatory cells occlude the aqueduct of Sylvius. If head injury is complicated by intraventricular bleeding, fragments of red blood cells may obstruct the aqueduct of Sylvius. This can produce an acute obstructive hydrocephalus with an acute rise in ICP following a head injury; unlike other causes of posttraumatic hydrocephalus, acute obstructive hydrocephalus may develop during the first hours after injury. It may also be associated with more gradual development of hydrocephalus and increased ICP.

Other causes of obstructive hydrocephalus include tumors and increased ICP that can compress the third and fourth ventricles, obstructing CSF flow. This form of obstructive hydrocephalus will compromise the patient’s ability to compensate for additional increases in intracranial volume. Obstructive hydrocephalus may be surgically treated through insertion of a drain or shunt.

Decreased CSF reabsorption causes communicating hydrocephalus. This complication may develop if head trauma is associated with a significant subarachnoid hemorrhage. Because CSF is reabsorbed by the arachnoid villi in the subarachnoid space, the presence of a significant amount of blood can compromise CSF reabsorption. A choroid plexus tumor is a rare cause of communicating hydrocephalus. All of these conditions result in CSF accumulation and can produce increased ICP.

Mass Lesions

Brain tumors are the most common solid tumor of childhood.⁵⁵ The tumors are typically infratentorial, located near or in the brainstem, and most contain glial cells (see Intracranial Tumors in the Specific Diseases section of this chapter). Intracranial hypertension can result from the tumor mass itself, from edema generated by the tumor presence, or from obstruction of CSF flow.

Intracranial Pressure and Volume

As noted previously in this chapter (see Essential Anatomy and Physiology, Intracranial Pressure and Volume Relationships), the intracranial vault is a relatively fixed space that contains the brain, blood, and CSF. When the volume of any of these components increases, venous capacitance blood is displaced from the intracranial vault, and, unless hydrocephalus is present, CSF is displaced into the subarachnoid space along the spinal column. Initially, these compensatory mechanisms may prevent a rise in ICP.

Once the limits of compensation and compliance have been reached, however, further increase in intracranial volume will produce a rise in ICP. The increase in ICP then becomes nearly exponential; progressively smaller increases in intracranial volume will produce progressively greater rises in ICP.

Intracranial Compliance

The shape of the intracranial pressure–volume curve reflects intracranial compliance. Intracranial compliance is the change in ICP that occurs with a given increase in intracranial volume (ΔVolume/ΔPressure). Initially, as intracranial volume increases, intracranial compliance is high and the curve is virtually horizontal; an increase in intracranial volume initially will be tolerated without a significant change in ICP. Once the limit of intracranial compliance is reached, intracranial compliance is then very low and the curve becomes virtually vertical; at this point even a small increase in intracranial volume will produce a significant rise in ICP.

Intracranial compliance is affected by time. If the intracranial volume increases gradually, as occurs with a slow-growing brain tumor, a significant volume may be accommodated without a rise in ICP because physiologic compensatory mechanisms have time to develop. In contrast, if the intracranial volume increases rapidly, as occurs following an intracranial hemorrhage, there is little time for compensation, and the ICP is likely to rise rapidly.¹⁰³

Intracranial compliance also is affected by previous rises in intracranial volume and pressure. Frequent spikes in the ICP will decrease intracranial compliance, resulting in a rise in ICP with subsequently smaller and smaller increases in intracranial volume. For example, consider the child with a head injury who develops an increase in CBF and CBV associated with hypercarbia, hypoxemia or seizures. During the initial episode of hypercarbia or hypoxemia or an initial seizure, the increase in CBF and CBV may be tolerated with only a mild rise in ICP. Subsequent similar episodes of hypercarbia or hypoxemia or additional seizures are likely to cause more substantial increase in ICP. A change in compliance alters the relationship between intracranial volume and pressure (Fig. 11-11).

Fig. 11-11 Changes in intracranial pressure (ICP) with changes in intracranial compliance. The relationship between intracranial volume and pressure is not static and is affected by intracranial compliance. Curves A, B, and C depict progressively lower intracranial compliance. When the increase in volume is gradual (curve A), more volume is tolerated before ICP begins to rise because intracranial compliance is initially high. When the intracranial volume increases rapidly, ICP will begin to rise with a smaller volume change (curve B), reflecting lower intracranial compliance. Once the ICP begins to spike, intracranial compliance is low, and progressively smaller increases in volume will produce significant ICP spikes (curve C).

Two terms that are used to quantify the intracranial compliance are the volume pressure resistance index and the pressure-volume index. These terms can roughly indicate the patient’s intracranial compliance (i.e., location on the pressure volume curve) and whether the limits of intracranial compensation have been reached.

The volume pressure resistance index or response was described by Guertin et al. in 1982.⁵⁴ Under a research protocol involving children with ICP monitoring in place, physicians gently instilled a known quantity of normal saline (typically 1   mL) into the child’s lateral ventricle. The greater the rise in ICP produced by the 1-mL instillation, the lower the intracranial compliance. For example, if instillation of 1   mL of saline produced an approximately 1   mm Hg rise in ICP, the patient’s intracranial compliance was characterized as high, as depicted on the relatively horizontal part of an intracranial pressure-volume curve. If, however, instillation of 1   mL of normal saline produced a rise in ICP of 7 to 10   mm Hg, the patient’s intracranial compliance was characterized as very low, as depicted by the relatively vertical part of an intracranial pressure-volume curve. In patients with low intracranial compliance, instillation of progressively smaller quantities of normal saline resulted in progressively greater rises in ICP (such as shown in Fig. 11-11, curves B and C).

Normal saline is rarely instilled into a lateral ventricle of a critically ill patient with increased ICP. However, it is easy to imagine the addition of 1   mL of CBF and CBV to the intracranial vault (e.g., with vasodilation that results from mild hypoxemia or hypercarbia during suctioning) and its effect on ICP. The change in intracranial compliance that occurs with repeated episodes of increased intracranial volume explains why a patient may tolerate suctioning once with only mild increases in ICP, but the same patient will demonstrate a dramatic elevation in ICP if a second episode of suctioning creates hypercarbia, hypoxia, or increased venous pressure.

Complications of Increased Intracranial Pressure

Unchecked increases in ICP may compromise cerebral perfusion or produce shifting of brain tissue (cerebral herniation). Complete brainstem herniation will produce interruption of cerebral perfusion and brain death.

Transtentorial herniation occurs when part of the brain herniates downward around the tentorium cerebelli. This herniation can occur in the anterior or posterior portions of the brain, and it may be unilateral or bilateral. Transtentorial herniation initially will produce pupil dilation (unilateral or bilateral) with a decreased response to light and impeded upward gaze. It also may produce obstruction of the Sylvian aqueduct with resulting CSF accumulation and a progressive rise in ICP. If large portions of the brain herniate across the tentorial notch, compression of vital brain structures causes death (see Evolve Fig. 11-3 in the Chapter 11 Supplement on the Evolve Website for illustrations of herniation).

Temporal lobe herniation (or uncal herniation) occurs when the temporal lobe shifts laterally across the tentorial notch. This herniation produces compression of the third cranial nerve and unilateral pupil dilation. If the brain continues to herniate through the tentorial notch, flaccid paralysis, pupil dilation, and death result.

The cerebellar tonsils can herniate through the foramen magnum without the development of any symptoms. However, some patients may develop a stiff neck, upper arm and shoulder paresthesia, a change in the respiratory pattern, or a wide fluctuation in heart rate.

Brainstem herniation through the foramen magnum results in compression of the vital cardiorespiratory centers and brain death.

Evaluation of Airway and Oxygenation

The first step in the evaluation of the patient with increased ICP is the evaluation and support of the airway, oxygenation, and ventilation. Increased ICP may be associated with decreased level of consciousness and an inability to protect the airway. In addition, loss of consciousness can result in airway obstruction by the tongue. Finally, apnea or hypoventilation may produce a rise in PaCO₂ and hypoxemia, resulting in an increase in CBF and a possible increase in ICP.

Evaluation of Systemic Perfusion

Monitoring of systemic perfusion is essential for all critically ill or injured patients. If systemic perfusion is poor, cerebral perfusion is likely to be compromised. This concept is especially true for the trauma patient with head injury. Thus, shock resuscitation and support of circulation are essential to optimizing cerebral perfusion.

Children with increased ICP may demonstrate a compromise in systemic perfusion. Tachycardia or bradycardia may be present and the skin may be mottled in appearance.

Hypertension may develop as a compensatory mechanism to maintain cerebral perfusion in patients with an increase in ICP, but hypertension also may be a sign of pain or fear. If hypertension develops, the nurse should immediately assess and support the airway, ventilation, and oxygenation and should evaluate the child’s heart rate, level of consciousness, and motor function, and pupil size and response to light. Significant hypertension, particularly if associated with any other signs of deterioration, should be reported to the on-call provider; it may signal increased ICP and even impending herniation.

Level of Consciousness

Evaluation of the child’s level of consciousness is probably the single most important aspect of neurologic assessment of the child with increased ICP. The level of consciousness must be evaluated on a regular basis and whenever changes are observed in the child’s clinical appearance, or cardiopulmonary function or in the monitored ICP or CPP (see Box 11-2).

Signs of a decreased level of consciousness in infants include lethargy, decreased eye contact, poor visual tracking, and a change in feeding behavior, including vomiting. Children with a decreased level of consciousness may be very irritable or lethargic, may be confused about where they are, may forget the names of family members or pets, or may appear drowsy. Decreased response to painful stimuli is abnormal in infants or children of any age and should be reported to the on-call provider immediately.

Pupil Response and Cranial Nerve Function

The pupils are normally the same size, and brisk pupil constriction in response to light is produced by innervation of the third cranial (oculomotor) nerve. When increased ICP develops, the oculomotor nerve is compressed by either general expansion of the brain, an intracranial lesion, or uncal herniation. Such compression can produce pupil dilation and decreased or absent pupil constriction in response to light. When the intracranial lesion or herniation is unilateral, the pupil dilation will occur on the same side as (ipsilateral to) the lesion. Compression of the third cranial nerve may cause unilateral ptosis in conjunction with pupil dilation. The child also may complain of blurred vision or diplopia.

Evaluation of the function of most cranial nerves can be performed during routine nursing care (see Table 11-2 and Box 11-2). If the child demonstrates a loss of previously demonstrated cranial nerve function, notify the on-call provider immediately. When cerebral perfusion is compromised and cessation of brain function occurs, cranial nerve function will disappear (e.g., the child who had a gag reflex will no longer cough or have a gag during suctioning).

Changes in Motor Function and Reflexes

The infant or child who develops increased ICP may demonstrate few spontaneous movements and may be unable to perform motor skills previously demonstrated. Development of incontinence in a child who previously had bowel and bladder control is a worrisome sign and may indicate significant deterioration.

Increased ICP will produce decreased motor function and possible abnormal posturing or reflexes, such as decorticate or decerebrate posturing (see Fig. 11-9). With progressive neurologic deterioration, flaccid paralysis will result.

If the child is obtunded or comatose, assessment requires evaluation of the child’s response to a central painful stimulus to determine whether a response occurs and if it is purposeful. A central painful stimulus is administered over the torso and can include rubbing of the sternum or pinching of the trapezius muscle. A peripheral painful stimulus, such as pinching of the fingernail, should not be used to evaluate purposeful response, because withdrawal of the extremity can occur as a result of only a spinal cord level reflex that requires no higher CNS function. Such withdrawal may still be observed after brain death or spinal cord transection.

The child demonstrates a purposeful response to the central pain stimulus if the child grasps and tries to move the hand that is administering the stimulus. Non-purposeful responses may include vague movement during the stimulus or groaning. To evaluate withdrawal from a painful stimulus, pinch the medial aspect of each extremity; withdrawal will cause abduction (movement outward from midline) of each extremity.

Decorticate posturing is the highest reflexive level of response to stimulus. Decerebrate posturing is a lower level of reflexive response to painful stimulation. Flaccid paralysis is the lack of any movement in response to deep painful stimulation. A provider should be notified immediately if the child’s response to central painful stimulus deteriorates.

It is important to evaluate changes in motor response in context with all other assessments of neurologic function. For example, if a child demonstrates decorticate posturing in response to pain with brisk pupil response to light, an ICP of 18   mm Hg, and appropriate heart rate and respiratory rate for age on admission, and then begins to demonstrate decerebrate posturing, tachycardia, hypertension, pupil dilation, and an ICP of 32   mm Hg, these findings are consistent with neurologic deterioration. Immediately notify an on-call provider of deterioration in motor activity and response. Flaccidity in response to painful stimulus can indicate spinal cord injury or severe neurologic dysfunction.

Alterations in Respiratory Pattern

The patient with increased ICP may demonstrate a wide variety of respiratory patterns (see Fig. 11-7). When ICP rises and the Cushing reflex is initiated, respirations become irregular, and apnea then respiratory arrest can develop. However, other breathing patterns also may be noted before the Cushing reflex develops.

The Cushing Reflex

The Cushing reflex produces the Cushing triad, three late and ominous signs of increased ICP that result from ischemia of the vasomotor center.⁸³ The Cushing triad may appear only when cerebral brainstem herniation is imminent. This triad consists of bradycardia, an increase in systolic arterial blood pressure (as an attempt to maintain CPP) with widened pulse pressure, and abnormal breathing pattern, typically apnea.⁸³

This reflex does not develop completely until ICP is elevated significantly. Earlier signs of increased ICP may include tachycardia and fluctuations in arterial blood pressure. Hypotension can develop late with increased ICP.

Papilledema

Papilledema is edema around the optic nerve and disc that results from increased ICP and compression of these structures. When an ophthalmoscope is used to examine the retina, the optic disc appears indistinct and the retinal veins are engorged and pulseless. Papilledema develops when ICP has been elevated for 48   hours or more (e.g., caused by a brain tumor). Therefore, papilledema indicates that the increased ICP is not a recent development, but has been present for a considerable period of time; this may aid in the identification of inflicted trauma.

When mild papilledema is present, the child’s vision should be normal. With progressive compression of the optic disc, however, hemorrhages can develop in the optic disc and the child may complain of headaches, blurred vision, or diplopia.

Scoring Neurologic Function

The most widely used neurologic scoring system is the GCS. This scale evaluates motor activity, verbal responses and motor responses, with a total scale range of 3 to 15 (see Table 11-6)

The GCS was validated in adults, so the verbal section cannot be used as written in the care of the preverbal patients. As a result, modifications of the GCS have been developed and found to be useful for pediatric patients with neurologic injury or disease (see Table 11-6).^{34a,83,93,106} The verbal section can’t be used as written for intubated patients. When the patient is intubated, it is very important for healthcare providers to identify a consistent approach to either modified application or omission of the verbal portion of the GCS.

The specific scale or modified scale used to score the child’s neurologic function is probably less important than the consistency with which the scale is used. Any scale or scoring system is most useful if it enables identification of trends in the patient’s condition over time. Therefore, it is essential that every member of the healthcare team use the same scale and apply the scale in exactly the same way. If the scale used is incorporated into the medical and nursing care documentation templates, the assessment information derived from the tool is readily accessible.

When the child is comatose, careful evaluation of the motor response is extremely important. However, this section of the GCS is often applied inconsistently or incompletely. For this reason, details about assessment of motor function are listed under the GCS Score in Table 11-6 and Box 11-2.

Other Signs of Increased Intracranial Pressure

The infant with increased ICP is often extremely lethargic, with a high pitched cry. The infant’s anterior fontanelle is usually full and tense. With chronic increased ICP, the scalp veins may appear distended. The infant’s eyes may deviate downward, with sclera visible above the irises; this is often referred to as sunset eyes. The infant may become extremely irritable when the head is moved or the neck is flexed, and the infant may be uninterested in feeding, or may vomit frequently. If the increased ICP is of longer duration, the nurse may be able to palpate spaces between the cranial bones as the cranial sutures widen.

The verbal child with intracranial hypertension may complain of headache, nausea, vomiting, blurred vision, or diplopia. The child may demonstrate mood swings and also may be more lethargic, with periods of confusion. Slurred speech is common. Clinical signs of increased ICP are summarized in Box 11-3.

Neurogenic pulmonary edema occasionally complicates increased ICP. This pulmonary edema can develop suddenly and without warning. The mechanism of the pulmonary edema is unclear, but it appears to be related to development of increased systemic and pulmonary artery pressure in response to the intracranial hypertension. The pulmonary edema usually produces respiratory failure (i.e., hypoxemia with decreased lung compliance and increased respiratory effort). For further information about pulmonary edema, refer to Chapter 9.

Helpful Diagnostic Tests

Careful clinical assessment, ICP monitoring, and evaluation of cerebral venous or tissue oxygen saturation provide the most useful bedside information about the child’s neurologic status. In addition, the EEG may be used during barbiturate therapy to assess cerebral activity or to evaluate for subclinical seizure activity.

Computed tomography (CT) is extremely helpful in localizing mass lesions or intracranial bleeding or in determining the presence of diffuse cerebral edema or infarction. (See the Common Diagnostic Tests section, later in this chapter, for further discussion of EEG and CT). The CT scan may be used in the acute management of the patient with increased ICP to evaluate potential causes of deterioration and to assess for the presence and severity of cerebral edema. If the third and fourth ventricles are widely patent and visible on a CT scan, the patient’s intracranial volume has not yet reached the limits of intracranial compensation (Fig. 11-12, A). If the third and fourth ventricles are collapsed and the basilar cisterns are obliterated, CSF has been displaced from the intracranial vault and the patient probably is reaching the limits of intracranial compensation, so intracranial compliance is low. Further increase in intracranial volume is likely to produce a significant increase in ICP, and cerebral herniation is possible. Collapse of the lateral ventricles (in the absence of an external CSF drain) also indicates that intracranial compliance is low (see Fig. 11-12, B and C).

Fig. 11-12 Computed tomography (CT) scans. The front of the patient’s head is at the top of each image (indicated), and the patient’s right and left sides are labeled. The viewer should imagine looking up into the intracranial vault (patient’s left is on the viewer’s right). A, The fourth ventricle is widely patent in this 11-year-old girl. It is visible as a horseshoe-shaped fluid-filled density (arrow). B, In contrast, a similar view from a 5-year-old boy shows no fourth ventricle. This child sustained a massive head injury and arrived at the hospital with signs of increased intracranial pressure and dilated and fixed pupils. The fourth ventricle is completely collapsed. White patches in occipital area are areas of subarachnoid hemorrhage (also present in C). C, This CT scan is from the patient in B. The lateral ventricles are visible but collapsed (small arrows), indicating displacement of cerebrospinal fluid from the intracranial vault with severe increase in intracranial pressure. D, In this CT scan of a 5-year-old boy who suffered a sudden intracranial hemorrhage, blood is visible in the fourth ventricle as a white or radiopaque density. E, In this CT scan of a young man with a self-inflicted gunshot wound to the right temple, the soft-tissue swelling is apparent over the right temple, and the track of the bullet fragments (the metal of the bullet is radiopaque) can be seen easily. The bullet crossed the midline, and blood (white or radiopaque) is visible in the lateral ventricles and between the cerebral hemispheres. F, The CT scan also will demonstrate significant alteration in cerebral circulation or tissue viability. This CT scan of a 6-year-old girl with acute nonlymphocytic leukemia and hyperleukocytosis was performed because the nurse noted the sudden onset of the right-sided weakness during examination. Soon afterward, the child’s left pupil dilated. A left cerebral infarction is apparent, producing a midline shift (arrow). Whitened areas of calcification indicate old embolic events. This child suffered a left hemisphere cerebral infarction secondary to embolism of adherent white blood cells. The right lateral ventricle is visible and dilated.

Magnetic resonance imaging (MRI) or magnetic resonance angiography may be helpful in the evaluation of stroke and other intracranial lesions. MRI also enables more definitive evaluation of intracranial masses and potential metastatic disease. It can provide useful information in confirmation of infectious disease of the brain and spinal cord.

If cerebral ischemia is suspected or brain death is thought to be present, a quantitative or qualitative radioactive cerebral perfusion scan may be performed. This study requires the injection of radioactive ^99mTc pertechnetate into the venous system and documentation of the absence of this substance in the cerebral vessels. For further information, see Cerebral Angiography in the Common Diagnostic Tests section of this chapter.

Assessment and Support of Airway and Ventilation

Whenever the child is at risk for increased ICP, the healthcare team must continually monitor the child’s airway and ventilation. If the child is obtunded or demonstrates a decreased response to painful stimulation, intubation with mechanical ventilation are indicated to prevent possible airway obstruction or respiratory arrest (Box 11-4). Intubation is also indicated if the child demonstrates hypoventilation or if signs of increased ICP are present.

Intubation of the child with increased ICP requires coordination of team activities to provide adequate preoxygenation, prevent development of hypoxia or hypercarbia during the attempt, and verify correct tube placement. Medications chosen for intubation should suppress awareness of and reflexes during direct laryngoscopy, to prevent a cough or gag that will further increase ICP. Succinylcholine is generally not the neuromuscular blocking agent of choice, because it can increase CBF and ICP. Other rapid onset neuromuscular blocking agents such as rocuronium are preferred (see Chapter 9 for additional information about Rapid Sequence Intubation).

Support of effective oxygenation and ventilation are critical throughout the treatment of increased ICP. Suctioning of the endotracheal tube may require two providers in order to prevent the development of hypercarbia and hypoxemia.

If the child coughs frequently or struggles against the ventilator, peak and mean airway pressures will rise and will impede cerebral venous return. If the child is struggling “against” the ventilator, verify oxygenation and tube patency and the position and appropriateness of ventilator settings. If oxygenation, airway patency and ventilator settings are adequate, sedation, analgesia, and possibly neuromuscular blocking agents with sedation may be needed to ensure effective control of ventilation (see Chapter 5).

Assessment and Support of Systemic Perfusion

The healthcare team will constantly assess the child’s systemic perfusion. The child’s color should be consistent, not mottled, and the nail beds and mucous membranes should be pink. Extremities should be warm with brisk capillary refill, and peripheral pulses should be readily palpable. Urine volume should average 1 to 2   mL/kg per hour if volume resuscitation and fluid intake are adequate. The child’s heart rate should be appropriate for age and clinical condition, and the blood pressure should be appropriate for age. Continuous monitoring of heart rate is required. Intraarterial pressure monitoring is indicated if intracranial hypertension is present or likely to develop.

Signs of poor systemic perfusion include a mottled color or pallor. The extremities will cool in a peripheral-to-proximal direction, and capillary refill will become sluggish. Oliguria will be observed, and the heart rate may be excessive or inadequate for clinical condition. The blood pressure may be normal or low in the presence of inadequate cardiac output and systemic perfusion. Alternatively, the blood pressure may be high if the child is agitated or in pain. A high systolic blood pressure with widened pulse pressure may indicate that ICP is high and cerebral herniation is imminent.

Treatment of inadequate systemic perfusion requires support of the heart rate, maintenance of an adequate intravascular volume relative to the vascular space, support of myocardial function, and manipulation of vascular resistance. Volume therapy is administered as needed to ensure adequate preload and intravascular volume. Inotropic support may be necessary if myocardial dysfunction is present.

If the patient remains hypotensive despite the presence of an adequate intravascular volume, vasopressors are indicated, and neurogenic shock may be present. If ICP increases every time the systemic arterial pressure rises, cerebral autoregulation has likely been lost; loss of autoregulation is a poor prognostic sign.

Intracranial Pressure Monitoring

ICP monitoring is a useful adjunct to clinical assessment of the child with neurologic insult or disease. Accurate ICP monitoring requires knowledge of the system and ability to troubleshoot the devices.

Methods

The ICP can be monitored in a variety of ways (for additional information, see Chapter 21). The most accurate method of ICP monitoring is through an intraventricular catheter (Fig. 11-13) using a fiberoptic or standard intraventricular catheter inserted into a lateral ventricle. Intraventricular monitoring is typically performed in combination with drainage of CSF.

Fig. 11-13 Locations for intracranial pressure monitoring.

(From Kee KR, Hoff JT: Youman’s neurological surgery, ed 4, Philadelphia, 1996, Saunders.)

Complications of intraventricular monitoring include infection, excessive drainage, difficulty in placement, and technical complications of a fluid filled system. Drains that are in place longer than 5 days increase the risk of infectious complications (this risk is about 5%).¹²³ Ventricular bleeding may develop during catheterization. Aspiration of the ventricular catheter is not recommended, because application of suction can tear or injure the choroid plexus, producing intracranial hemorrhage.

The intraparenchymal fiberoptic catheter is easier to place than the intraventricular catheter and offers accuracy that rivals intraventricular pressure monitoring, with a similar risk of infection. One disadvantage of this catheter is that it cannot be readjusted to a zero reference point after insertion, and its zero reference has a tendency to drift over time.¹²³

The subarachnoid bolt or screw can be placed through a burr hole in the skull into the subarachnoid space. Although this form of ICP measurement cannot be used in infants, it can provide a relatively reliable form of ICP monitoring with a low complication rate for children. Epidural catheters are occasionally used.

Nursing Responsibilities

When an ICP monitor is in place, the nurse is responsible for monitoring trends in the ICP, identifying worrisome changes in ICP, evaluating accuracy of the ICP measurements, and ensuring safety of the system (see Chapter 21 for information regarding the insertion and maintenance of ICP monitors). Throughout ICP monitoring, the nurse should immediately notify the appropriate physician or on-call provider of any deterioration in the child’s clinical status, an increase in the child’s ICP above the threshold reporting request, dampening of the ICP waveform, or malfunction of the ICP system.

If an extraventricular drainage (EVD) system is in place, the nurse should obtain orders regarding the height for placement of the drainage chamber (above the level of the child’s lateral ventricles), whether CSF drainage is to be continuous or intermittent, and actions to take if the ICP rises. Typically, the drainage port is placed at a specified height (typically ordered in centimeters) above the patient’s lateral ventricles, and the drainage stopcock is open to allow drainage (Fig. 11-14). If the system is functioning and the stopcock is turned “open” to drainage, CSF will drain from the child’s ventricle into the collection chamber and ultimately into the drainage bag once the patient’s ICP is sufficiently high to equal or exceed the equivalent of centimeters of water (cm H₂O) pressure.

Fig. 11-14 Intraventricular intracranial pressure (ICP) monitoring system with an external ventricular drainage system for controlled drainage of cerebrospinal fluid. A, The system consists of an intraventricular catheter joined by tubing to a drainage system with adjustable height and a drainage bag. The system also typically has a stopcock, an injection sampling port, and a clamp. The zero reference point for the system is typically between the outer canthus of the eye and the external auditory canal (see leveling device placed at that level). B, The drip chamber pressure level (horizontal arrow) is placed a prescribed height (in cm) above this zero reference point. The drainage stopcock can allow continuous drainage or be turned to allow only intermittent drainage when the child’s ICP exceeds a prescribed threshold. If the system is functioning and the stopcock is turned to drainage, CSF will drain from the child’s ventricle into the collection chamber and ultimately into the drainage bag once the patient’s ICP is sufficiently high. If the drip chamber is placed 27.2   cm (rounded to 27   cm) above the child’s ventricles, drainage should occur if the child’s ICP equals 27.2   cm H₂O or 20   mm Hg (1.36   cm H₂O pressure = 1   mm Hg pressure; 27.2   cm H₂O pressure = 20   mm Hg pressure).

(Redrawn and modified from Owen A: Clinical guideline: external ventricular drainage. Great Ormond Street Hospital for Sick Children, Institute of Children’s Health and University College of London, Revised, September, 2009.)

If the EVD system is functioning correctly and the ventricles are not collapsed, the patient’s ICP during continuous drainage should never exceed the equivalent of the cm H₂O elevation of the drainage port above the child’s ventricles, because CSF will drain at that pressure. Note that the child’s ICP is typically monitored in millimeters of mercury, and the fluid-filled EVD system is operating with centimeters of water pressure. The following conversion factor is used:

Therefore, if the drainage chamber is placed 13.6   cm above the child’s ventricles and the stopcock is open to drainage, CSF should drain whenever the child’s ICP begins to exceed 10   mm Hg, and the ICP should not exceed 10   mm Hg unless the drain stopcock is closed. If the drainage chamber is placed 27.2   cm above the child’s ventricles, CSF will drain whenever the child’s ICP begins to exceed 20   mm Hg; therefore, the ICP should not exceed 20   mm Hg unless the drain stopcock is closed. If the ICP exceeds the drainage pressure with the stopcock open to drain, the nurse should search for obstruction in the tubing system and notify the appropriate on-call provider.

When intermittent drainage is ordered, the drainage stopcock is maintained in the closed position, and the nurse opens it to allow drainage of CSF if the ICP exceeds a specified pressure, typically 20   mm Hg. Such intermittent CSF drainage enables better evaluation of the patient’s intrinsic ICP and the severity (magnitude) of any ICP spikes.

If drainage is intermittent, specific orders are needed regarding actions to be taken when the ICP rises (e.g., exceeds 20 to 25   mm Hg). For example, the provider may request that the child’s ventricular drain be opened for 5   minutes to drain CSF if the ICP rises above 20   mm Hg for more than 10   minutes, or that drainage continue until the child’s ICP is below a threshold. Any such orders must be clear (unambiguous) to protect the patient, the nurse, and the provider.

Transducers used for ICP monitoring must not be connected to standard infusion devices, because solution is not routinely infused into the subarachnoid space or ventricles. Occasionally, a provider may order instillation of a small amount of solution into the ICP catheter, but such instillation is performed only in the presence of the on-call provider with a specific order. A physician typically instills the solution. The ventricular catheter should not be aspirated, because application of suction can cause injury to the choroid plexus and intracranial hemorrhage.

The scalp entrance site of the intraventricular catheter should be covered with a clear bioocclusive dressing; this allows the nurse to examine the entrance site for evidence of inflammation while maintaining an airtight dressing. The dressings covering intradural, subdural, and epidural monitors should be as occlusive as possible.

Tubing and drainage systems used for ICP monitoring should be changed per institutional policy and manufacturer’s recommendations, using sterile technique. This procedure usually requires two people, with one person maintaining sterility during the process (the other person assisting). Care must be taken to avoid any break in sterile technique that could contaminate the system; contamination can lead to ventriculitis or meningitis and worsening of the patient’s condition.

Documenting the ICP

The ICP documented on the nursing flow sheet or in the electronic record should reflect the peak ICP as well as the typical ICP that hour and the CPP during a monitoring interval (see Box 11-5 for one nurse entry method and Fig. 11-15 for sample screen from an electronic record). Such documentation provides more information than simple documentation of the ICP at one point in time, particularly if the ICP varies throughout the monitoring interval. If the nurse either documents or downloads the ICP measurement at a convenient time without ensuring that the pressure is representative, it will be more challenging to identify trends in the patient’s condition. The healthcare team can also examine graphic images or trends in the ICP over hourly, daily, or longer intervals; such evaluation is better than review of isolated pressure measurements.

Box 11-5 Hourly Documentation of Intracranial Pressure

↑42 = highest ICP observed that hour

* = ICP peak occurred only with stimulation (if no asterisk indicated, the ICP peak occurred without stimulation)

CPP, Cerebral perfusion pressure; ICP, intracranial pressure.

Fig. 11-15 Documentation of intracranial pressure in electronic record.

If the child’s ICP is elevated, it is helpful to note whether the ICP spikes are spontaneous or occur only with stimulation. If a spike in ICP with stimulation (e.g., suctioning, painful stimulus) is recorded, the source of stimulation should be noted in the record. The healthcare team should be aware of trends in the patient’s ICP, including spikes and typical ICP. If the patient’s intracranial compliance is low, the ICP will peak at higher levels, even without stimulation, and the average ICP will be higher than if the intracranial compliance is high. As the patient recovers, the ICP peaks will be lower and may occur only with stimulation. In addition, the average ICP will fall as intracranial compliance improves.

One or more of three distinct pressure waveforms, designated A, B, and C, may be visible when the ICP waveform is displayed on an oscilloscope. A waves are commonly called plateau waves, and they usually range in amplitude from 50 to 100   mm Hg. These plateau waves usually appear in patients who already have elevated ICP; they represent a further critical rise in the ICP associated with factors such as hypercapnia, hypoxia, or cerebral edema. Because the appearance of A waves is extremely worrisome and usually is associated with other signs of neurologic deterioration, their appearance warrants immediate notification of an on-call provider.

B waves are sharp, rhythmic, low-amplitude waves that fluctuate during the respiratory cycle. These waves usually range in amplitude from 20 to 50   mm Hg and indicate decreased cerebral compliance. They may precede the development of A waves.

C waves are also rhythmic, low amplitude waves. They are related to normal changes of the systemic arterial blood pressure and ventilation, and their clinical significance is not clear.⁶²

Reduction in Cerebral Blood Volume

Support of mechanical ventilation is generally provided to maintain the arterial carbon dioxide tension at approximately 35 to 40   mm Hg, the arterial oxygen tension at 80 to 100   mm Hg, and the oxyhemoglobin saturation at 95% to 97%. Hypercarbia and hypoxemia must be prevented, because they cause cerebral vasodilation that will increase CBF and will likely contribute to a further rise in the ICP.

An acute reduction in CBV can be achieved through hyperventilation and the creation of hypocarbia. Hyperventilation is not recommended for long-term management of increased ICP. Mild hyperventilation (to a PaCO₂ of 30-35   mm Hg) can be used in the presence of an acute neurologic deterioration and fear of impending herniation.⁹ If the child is not intubated, the CBV may be acutely reduced using bag-mask ventilation, but intubation and mechanical ventilation are ultimately required.

If the child develops alkalosis (respiratory or metabolic), the child’s oxyhemoglobin dissociation curve will be shifted to the left; this increases the risk of cerebral hypoxia and reflex cerebral vasodilation for two reasons. A shift in the curve to the left increases hemoglobin saturation at any arterial oxygen tension (PaO₂), so that even mild-to-moderate hemoglobin desaturation (e.g., 90%) may be associated with significant hypoxemia (e.g., PaO₂ of 50-60   mm Hg). In addition, a left shift of the oxyhemoglobin dissociation curve results in compromise of oxygen release at the tissue level. Therefore, the hemoglobin saturation should be monitored continuously using pulse oximetry, and maintained at 95% to 97% saturation, and alkalosis is avoided.

Skillful pulmonary support and suction technique is required to prevent hypoxemia and any rise in arterial carbon dioxide tension. Monitoring of pulse oximetry and end-tidal or exhaled CO₂ is extremely useful in accomplishing this goal. Breath sounds must be assessed frequently, and atelectasis and hypoventilation must be prevented or detected and treated.

Neuromuscular blockade with sedation and analgesia may be necessary to control ventilation.⁷ Support of ventilation is adjusted to avoid high peak inspiratory pressure and high positive end-expiratory pressure, because high intrathoracic pressure will impede cerebral venous return. Any pneumothorax must be immediately detected and decompressed to avoid impeding cerebral venous return.

Cerebral venous return is enhanced by elevation of the patient’s head in a midline position. The optimal degree of elevation is not clear. Most sources suggest that elevation of 15° to 30° is optimal, with adjustment to minimize intracranial hypertension while optimizing CPP.

Keeping the head in midline also facilitates venous return. If the child’s ICP is normal and intracranial compliance is high, turning of the head may produce no change in ICP. However, if the ICP is elevated and intracranial compliance is low, turning of the head may result in a substantial rise in the ICP.

Maintenance and Manipulation of Serum Osmolality

Serum osmolality is typically maintained at approximately 300-310   mOsm/L (normal: 275-295   mOsm/L). Any rapid fall in serum sodium and osmolality, as can occur after administration of a large volume of hypotonic fluid, must be avoided because such a fall will produce a sudden shift of free water into the cells, contributing to cerebral edema.

Serum osmolality exceeding 320 to 340   mOsm/L has been associated with renal dysfunction and increased mortality in patients with head injury when using mannitol as the osmotic agent.^8,70 However, recent studies suggest that when using hypertonic saline solution, serum osmolality as high as 360   mOsm/L may be acceptable without adverse effects.

The healthcare team must closely monitor the child’s serum electrolytes during therapy. The osmotic diuretic effect of mannitol can produce the loss of free water and electrolytes, leading to fluid and electrolyte imbalance and possible hypotension. This hypotension can compromise cerebral perfusion, producing secondary injury in an already compromised brain. Hypertonic saline does not cause the same diuresis and may improve hemodynamics.^8,70

Drainage of Cerebrospinal Fluid

A reduction in CSF volume is necessary if hydrocephalus is present. This reduction is achieved by surgical insertion of a ventriculoperitoneal shunt or other form of ventricular drain. If the child has such a shunt in place, the healthcare team must determine and document whether the shunt must be pumped regularly to maintain function. Shunts should be pumped only with an order from the physician or other on-call provider or per institutional policy. Shunts can malfunction, become obstructed, or become disconnected during the immediate postoperative period or anytime after insertion, resulting in a gradual or acute increase in ICP.

Even if CSF volume is not increased or excessive, reduction in CSF volume can be used to reduce intracranial volume and pressure. This can be accomplished using an intraventricular catheter to drain CSF. This extraventricular drain (EVD) can be intermittent or continuous (see Fig. 11-14). The collection chamber is positioned at a constant prescribed level above the patient’s lateral ventricles (leveled at the anatomic landmark of the outer canthus of the eye, the external auditory canal, or a space between these points); the higher the collection chamber above the lateral ventricles, the higher the ICP required to produce CSF drainage. Rapid drainage of a large volume of CSF is not recommended, because upward herniation of the brain can occur. If an EVD is in place, strict sterile technique is used whenever the drainage system is entered (per provider order or unit policy), for example, to change drainage bags.

A malfunctioning or infected shunt may be externalized distal to the valve and attached to an EVD system. While the set-up and general care are similar to those described for use of an intraventricular catheter, the nurse must understand that CSF drainage is also influenced by the valve function.

CSF drainage should be performed with some caution. The most common complication of external CSF drainage is infection, although the incidence is low. The other common complication is loss of waveform transmission, typically secondary to obstruction of the catheter or drainage system. This complication can result from the presence of tissue or a clot within the system or from complete collapse or compression of the ventricular system in the setting of extremely elevated ICP. There are no pediatric data documenting the incidence of complications such as brain injury, hemorrhage, or seizure related to the placement of these drains, although the incidence of these noninfectious complications is thought to be low.⁶

A less commonly used device for removal of CSF is the lumbar drain. The lumbar drain is a sterile, continuous drainage device that diverts CSF from the subarachnoid space. While the lumbar drain is used primarily for the management of postoperative CSF leak, management of shunt infections, and for the diagnosis of idiopathic normal pressure hydrocephalus, it has been used in the operating room during a craniotomy to reduce ICP and as adjuvant therapy in patients with increased ICP secondary to traumatic brain injury. Experimentally lumbar drains have been used in the management of subarachnoid hemorrhage (SAH).

As with the EVD, the lumbar drain collection device is leveled at a predetermined position. The level of the transducer is dependent on the goal of therapy: draining at a precise level, draining at a specified volume, or draining at an established pressure. If the lumbar drain is being utilized in conjunction with an EVD for treatment of increased ICP then the collection chamber should be raised to the same level as the drain of the EVD. The tragus is typically used as the zero reference point.^125a

General Supportive Care and Control of Oxygen Requirements and Nutrients

As noted previously, the patient with increased ICP should be intubated and mechanically ventilated. If the patient is agitated, sedation is indicated. Adequate analgesia must always be provided, because pain can contribute to a rise in ICP. If work of breathing is increased or agitation continues, sedation and analgesia with neuromuscular blockade may be required during mechanical ventilation. Of course, providers should closely monitor oxygenation and ventilation to ensure that both are adequate. Auditory stimulation should be minimized, because it can also contribute to a rise in ICP.

The child’s temperature should be controlled to maintain normothermia and prevent elevation in temperature. Fever is detrimental to the injured brain because it increases the metabolic and oxygen requirements, so it is important to prevent and immediately treat any elevation in temperature above normal. Fever is typically treated with antipyretics and possibly a cooling device. If a cooling device is used, monitor for shivering. Shivering will increase metabolic demand and increase ICP; if shivering develops, it may be necessary to adjust cooling or (assuming mechanical ventilation is provided) administer a neuromuscular blocking agent with sedation.

The role of therapeutic hypothermia remains controversial in pediatric traumatic brain injury (see Additional Controversial Therapies). If therapeutic hypothermia is utilized, the child is cooled to approximately 32° to 34° C; sedation or sedation with neuromuscular blockade is generally required to prevent shivering.

Seizures can complicate the management of the child with increased ICP. Because seizures increase CBF and metabolic rate, they require treatment. Status epilepticus can create an acute and severe rise in ICP and should be suspected in any child with head injury who demonstrates sudden neurologic deterioration, pupil dilation, and fluctuation in vital signs.

The use of prophylactic anticonvulsants in pediatric patients with head injury is controversial. Current guidelines recommend the use of anticonvulsant therapy to prevent seizures in high-risk pediatric patients during the first week following a traumatic brain injury, noting that infants and small children are at greater risk for early posttraumatic seizure activity than are older children and adults.¹⁴ Late prophylaxis (after the first week) should not be used.

Anesthetic, sedative, analgesic, and neuromuscular blocking agents (lidocaine, fentanyl, midazolam, vecuronium) are often administered to reduce the cerebral metabolic rate and improve the cerebral oxygen delivery and supply relationship (see Chapter 5 for information about the drugs). The use of barbiturates is reviewed in “Barbiturate therapy,” below.

If the child appears agitated but does not respond in a purposeful manner to questions, it may be difficult to determine whether the child is in pain or is simply agitated as the result of a decreased level of consciousness. Treatment of pain is always important, and treatment of episodes of agitation will be necessary if they contribute to increased ICP or interfere with care. The healthcare team should have an organized and consistent approach to this challenge (e.g., sedative administration, reassessment, and administration of an analgesic if agitation continues).

Once the child is stable, nutritional support is needed. Gastric feedings may be initiated if the child demonstrates an effective cough and gag reflex. Transpyloric feeding may be undertaken if the child is intubated and sedated or the patient is thought to be at risk of aspiration. Parenteral alimentation should be reserved for patients who cannot tolerate enteral feeding or who have other injuries for which enteral feeding is contraindicated. Some nutritional support should be initiated by 48 to 72 hours after admission and full support should be provided by the end of the first week.

Gastrointestinal function should be monitored closely, and stress ulcer prophylaxis provided until feedings are initiated. Stool softeners should be administered as needed. Unless contraindicated, the head of the bed should be elevated to 30 degrees, to decrease risk of aspiration and ventilator-associated pneumonia. Regular oral care and frequent assessment of endotracheal secretions should be instituted (per protocol to prevent ventilator-associated pneumonia) to detect, prevent, or minimize the risk of pneumonia associated with aspiration (see Chapter 9).

Uncontrolled endogenous or exogenous hyperglycemia can be harmful to critically ill patients and can increase complications and decrease survival. Hyperglycemia is associated with a worse outcome in children with head injury and following cardiac arrest, but it is unclear whether the hyperglycemia is the cause or a symptom of the problem. Insulin infusion to prevent hyperglycemia has been associated with reduced ICU mortality in adult studies and in one multicenter pediatric study,¹²⁸ but it will increase hypoglycemic episodes. The relative risk of hyperglycemia and potential harm from hypoglycemia must be considered when contemplating insulin infusion for glucose control. If an insulin infusion is provided to control hyperglycemia, it is typically used during the first 12 to 18 hours of critical care, with careful monitoring of serum glucose concentration (using point of care testing, if possible). A glucose infusion may be added and titrated to prevent significant hypoglycemia during the insulin infusion.

Barbiturate Therapy

Barbiturate therapy may be prescribed for children with severe intracranial hypertension that is refractory to hyperosmolar therapy, sedation, analgesia, neuromuscular blockade, and CSF drainage. There are currently no data to support the use of barbiturates for prophylactic neuroprotection or prevention of intracranial hypertension.

Barbiturates lower ICP by suppression of metabolism and alteration in vascular tone, thereby improving the oxygen delivery-to-consumption ratio in patients with compromised cerebral perfusion. The anesthetic effect of the barbiturate will lower ICP. However, if the vasodilatory effect of the barbiturate reduces the MAP, cerebral perfusion will likely be compromised. Therefore, when barbiturates are administered, cardiovascular function must be closely monitored and supported.

If a barbiturate-induced coma is planned, an arterial and a central venous pressure monitoring catheter should be in place. Intravascular volume must be adequate before the infusion of the barbiturate is initiated, or hypotension will likely ensue. A continuous infusion of dopamine or epinephrine should be prepared and available at the bedside, to be administered as needed (with provider order) to maintain the MAP (and CPP).

As noted previously, barbiturates can produce hypotension and myocardial depression with a resultant fall in cardiac output and compromise in systemic and cerebral perfusion. Cardiac output can be maintained during barbiturate therapy with volume infusion and inotropic drug support. The goal of barbiturate therapy is to improve cerebral perfusion. As a result, the ICP should fall while the MAP is maintained. The child’s systemic perfusion should be monitored constantly during barbiturate therapy.

Thiopental, phenobarbital, or pentobarbital may be administered to induce coma. Thiopental is used most often for short-term anesthesia. Pentobarbital usually is preferred for continuous infusion because it has a shorter half-life than phenobarbital, so a shorter time is needed between cessation of therapy and drug elimination (i.e., drug concentration becomes subtherapeutic—and the patient should awaken—more rapidly after infusion is discontinued). An initial pentobarbital loading dose of 10 to 15   mg/kg is administered, followed by a continuous infusion of 1   mg/kg per hour.^10,120 The dose is increased until coma is achieved.

A rare complication of pentobarbital infusion is propylene glycol toxicity. Propylene glycol is the vehicle in which pentobarbital intravenous (IV) formulation is prepared. If large amounts of pentobarbital are administered in a short period of time, propylene glycol toxicity may result. Initial signs of toxicity include hyperosmolarity and lactic acidosis, which can cause renal dysfunction and multisystem organ failure.^24,88 During barbiturate therapy, the healthcare team should monitor for signs of toxicity.

Once coma is induced, the presence of coma is verified by observation of a “burst suppression” pattern on a bedside EEG monitor or the obliteration of any response to painful stimulation. In general, cranial nerve function is abolished, although some pupil constriction in response to light may be observed during barbiturate coma. Brain stem-evoked potentials can be evaluated during this therapy.

If ICP is controlled effectively, the barbiturate therapy can be reduced approximately 24 to 36 hours later. During reduction in the barbiturate dose, the patient’s ICP, MAP, CPP, and neurologic function must be monitored closely.

Because barbiturates obliterate most neurologic function, the diagnosis of brain death will require the withdrawal of the barbiturate and/or the performance of confirmatory tests (e.g., cerebral perfusion scan) as dictated by institutional policy. If an EEG or clinical examination is used for confirmation of brain death, the serum barbiturate concentration must be subtherapeutic before the confirming EEG or examination is performed. Typically several days are needed between discontinuation of the barbiturate infusion and the fall in the barbiturate concentration to subtherapeutic levels.

Once medical therapy is maximized the only additional alternative to control increased ICP is decompressive craniectomy. This procedure is controversial and not employed in all centers. However, for patients with severe traumatic brain injury and refractory intracranial hypertension the procedure lowers ICP and may improve outcome. Removal of a portion of the skull, especially over the injured area allows additional room for the brain to swell without further restricting blood flow to the parenchyma. A decompressive craniectomy may be most beneficial in young patients with severe TBI and refractory intracranial hypertension from inflicted head trauma or those with some or all of the following: diffuse edema on CT scan, <48   hours post injury, no episodes of ICP >40   mm Hg prior to surgery and a GCS of >3 at some point after injury.^11a

Additional Controversial Therapies

Steroid administration does not improve survival or recovery from increased ICP caused by trauma or ischemia. It can, however, reduce cerebral edema in patients with mass lesions, specifically brain tumors or discrete hematoma¹²; these problems remain the only indications for the use of steroids in the treatment of increased ICP. Complications of steroid administration include gastrointestinal bleeding, hyperglycemia, and increased susceptibility to infection. When discontinuing steroid therapy that has been used for more than a few days, taper the dose gradually.

The use of therapeutic hypothermia is controversial for pediatric patients with increased ICP following traumatic brain injury. There are currently no data to support the use of therapeutic hypothermia except as treatment to be considered in cases of refractory intracranial hypertension.¹¹ There is some support for the use of therapeutic hypothermia in the adult and neonatal patients with presumed hypoxic-ischemic injury following cardiopulmonary resuscitation; its role in the pediatric population remains unclear and is currently under investigation.⁶³

Weaning from Support

As the child’s condition improves, neuromuscular blockade, sedatives, and analgesics are weaned and the child is allowed to wake, move, and begin gradual weaning from mechanical ventilation. To wean treatment, one change in treatment is made at a time to allow for thorough evaluation of the child’s response before a second change is made. If the child’s ICP begins to rise again, an on-call provider should be notified immediately and resumption of recently discontinued therapy should be considered. The development of hypercapnia, hypoxia, and hypoventilation must still be avoided, because these factors may still result in a rise in ICP.

Psychosocial Support

The child and family will require sensitive support. While the child is unstable, it is often necessary to focus on the technical aspects of the child’s care; however, the psychosocial aspects obviously cannot be neglected. If the nurse is unable to allow time or attention for supportive interaction with the family, an additional nurse, chaplain, or social worker should be called to provide the parents with the support they will need.

Throughout care, the child should receive explanations of all procedures performed and of all the things that will be seen, felt, or heard. Comatose children and those receiving neuromuscular blockade, sedation, and analgesia are still able to hear bedside conversation; therefore, the staff members should minimize technical discussions near the bedside and avoid discussion of a poor prognosis in the child’s presence. Too often severely ill children are treated as though they are unconscious when they are merely immobile. As the child becomes able to move, simple signals should be devised to allow the child to communicate, and all signals should be recorded carefully in the plan of care.

As children with intracranial hypertension recover, they should receive repeated explanations of where they are and how they are progressing, because they may be disoriented from the effects of medications or when waking from a sound sleep. It is natural for children to be frightened during this time.

If the child will require rehabilitative therapy, such therapy should be initiated as soon as possible so that the child’s progress or discharge from the unit is not delayed unnecessarily. Physical and occupational therapists should be consulted on admission to assist with prevention of contractures, foot drop, and other complications of long-term immobility. Prior to initiating oral intake, speech therapists should be consulted for evaluation of swallow. If the child is not expected to recover, each member of the healthcare team should be aware of the prognosis, the information provided to the family, and the family’s response to this information, so that consistent and constructive intervention can be planned (see the Brain Death and Organ Donation section in this chapter and see Chapter 3).

Support of Vital Functions

The patient’s airway must be kept patent and free of secretions. The comatose patient may be unable to cough effectively to keep the oropharynx and trachea free from obstruction by secretions. In addition, ineffective gag and uncoordinated swallow reflexes will increase the risk of aspiration of vomitus, oral secretions, or mucus.

The nurse should suction the pharynx as needed and position the patient so that oral secretions pool in the side of the mouth instead of in the pharynx. The tongue of the unconscious patient can obstruct the pharynx when the patient is supine; therefore, the patient is typically positioned with the head of the bed elevated and the patient’s head turned to the side (unless increased ICP is present). If secretion control or maintenance of a patent airway becomes difficult, intubation may be required.

If the child is breathing spontaneously, the nurse must constantly assess the effectiveness of the child’s ventilation and oxygenation. Air movement should be adequate and equal bilaterally, and signs of increased respiratory effort (retractions, nasal flaring, or grunting) should be absent. Elevation of the head of the child’s bed will allow maximal inspiratory effort by allowing abdominal contents to drop away from the diaphragm. Placement of a small linen roll under the child’s shoulders will support a patent airway.

If the comatose child is apneic, bag-mask ventilation and then intubation with mechanical ventilation are required. This assistance also is needed if the child develops hypercapnia, hypoxia, or inadequate inspiratory effort.

After the institution of mechanical ventilation, the child will require excellent pulmonary toilet using aseptic technique. Supplementary ventilation and preoxygenation must be provided before and immediately after suctioning to prevent carbon dioxide retention and hypoxemia during the suctioning attempt; this is especially important if the child is at risk for the development of increased ICP.

If the child has severe pulmonary dysfunction and alveolar hypoxia, attempts should be made to determine the position associated with the best arterial oxygen saturation and most efficient carbon dioxide removal. Dependent portions of the lung will receive the greatest blood flow, whereas the best aerated portions of the lung are often the nondependent lung segments. As a result, the nurse should document the child’s position when blood gases are drawn in an attempt to determine what effect, if any, the child’s position has on oxygenation and carbon dioxide elimination.

The comatose patient may not become agitated or restless when hypoxic and will be unable to articulate complaints. It is therefore extremely important that the nurse recognize signs of poor systemic perfusion or inadequate respiratory function.

When the child is comatose or when pharmacologic coma is induced, venous pooling of blood occurs⁴¹ and can produce a relative hypovolemia. The administration of additional IV fluids may be required to maintain an adequate central venous pressure and systemic perfusion.

If the comatose child is always kept in the recumbent position, orthostatic hypotension can result when the child initially resumes the upright position.⁴¹ In addition, the recovering child may be extremely frightened when immobilized in the supine position, with caretakers looming overhead. If possible the child should be placed in the semi-Fowler’s position several times each day. This position provides the recovering child with a different view of the unit, helps to prevent the development of orthostatic hypotension, and allows maximal diaphragm excursion and chest expansion. This positioning can be provided for the small infant through the elevation of the head of the crib mattress or the use of an upright infant’s seat.

The child’s hourly fluid intake and daily weight should be assessed carefully. Urine output should average 1   mL/kg per hour if fluid intake is adequate. If the child’s fluid intake or output is inadequate, it should be discussed with a provider.

Maintenance of Adequate Nutrition

As soon as the comatose child is admitted to the critical care unit, the healthcare team should plan to provide adequate nutrition. Fluid requirements can be delivered easily in the form of IV solutions, but maintenance calories may be more difficult to provide. If inadequate caloric intake is provided, the child will develop a negative nitrogen balance and a protein deficiency, wound healing will be delayed, the young infant will not be able to make the brown fat needed to generate heat, and general recovery will be slowed. Therefore, the team should plan to provide some form of enteral or parenteral alimentation.

If enteral feedings are attempted, small amounts of formula are initially provided, and the amount and concentration is then advanced slowly as tolerated. When continuous nasogastric feeding is tolerated, the child can be advanced to small bolus feedings. During this time, the nurse should measure and record the residual formula remaining in the stomach before feeding and should assess the child’s abdominal girth and firmness throughout the feeding. The comatose child might not tolerate enteral feedings, because immobilization may produce a paralytic ileus. If gastric distension, diarrhea, vomiting, or gastric reflux develops, enteral feedings should be discontinued, and parenteral alimentation should be instituted (see Parenteral Nutrition in Chapter 14).

Care should be taken to monitor the child’s acid-base and electrolyte status, supporting electrolyte and acid-base balance. This support includes the provision of daily electrolyte requirements and checking electrolyte concentrations at regular intervals or with changes in the patient’s condition.

A bowel regimen should be instituted to prevent constipation or bowel impaction. Stool output must be charted consistently so that the healthcare team does not overlook the absence of a bowel movement for several days. Use of glycerin suppositories or enemas may be required occasionally to promote the evacuation of stools.

Prevention of the Complications of Immobility

As soon as the status of the comatose child is stable, a referral should be made to occupational and physical therapists. Passive range-of-motion exercises are needed on a regular basis, and splints or ankle pads should be used to prevent ankle and wrist contractures, foot drop, and pressure sores.

Comatose children require excellent skin care. Foam or alternating-pressure mattresses or other pressure-relieving devices will help prevent the development of pressure sores over bony prominences. Careful assessment includes complete inspection of the child’s skin at least once every shift, unless the child is extremely unstable. Gentle massage over any reddened areas will promote circulation and reduce ischemia. The skin should be kept as dry as possible, and the sheets should be free of wrinkles. The development of skin breakdown signals inadequate attention to skin care.

The insertion of multiple invasive monitoring lines and drains and other tubes increases the patient’s risk of hospital-acquired infection. Good hand washing technique is one of the best ways to avoid the transmission of infection. Strict hand washing technique must be used when handling the patient catheters and tubes. Aseptic technique must be used when suctioning the ET tube. For additional measures to prevent ventilator associated pneumonias, see Chapter 9.

All skin puncture sites require inspection at least once each shift, with wound drainage, wound fluctuance, erythema, or odor reported to an on-call provider. Other signs of infection include an elevation in white blood cell count and fever. In small children, a decrease in platelet count can indicate the presence of sepsis and the development of disseminated intravascular coagulation (see Chapters 6 and 16). If infection is suspected, obtain appropriate wound, serum, or catheter cultures per order or protocol, and administer antibiotics as needed.

Comatose children typically have both bowel and bladder incontinence. However, a urinary catheter should not be inserted merely to simplify urine collection. Diapers, condom catheters, or padded rubberized sheets can enable measurement of urine output and minimize need for linen changes. If the use of a urinary catheter is required for ongoing evaluation of renal function and urine output, meticulous catheter and meatus care is required. If cloudy or foul smelling urine develops, notify an on-call provider and obtain urinalysis and urine culture (and Gram’s stain, if indicated) per order or protocol.

If the child’s blink reflex is not intact, apply ophthalmic ointment to lubricate the cornea and prevent corneal abrasions. It may be necessary to patch the eyes to protect the corneas. Before patch placement, both the child and the family should be told about the purpose of the patches.

The child’s mouth requires lubrication and cleaning several times each shift to prevent the development of gingivitis or dental caries. The child’s mouth and lips should be kept clean, even if they are covered with the tape holding the ET or nasogastric tube in place.

Immobilized adolescents and preadolescents are at risk for development of deep venous thrombosis. This subpopulation of pediatric patients requires deep venous thrombosis prophylaxis using thromboembolic deterrent (TED) hose, sequential compression devices and/or low-molecular weight heparin (per order or institutional preference or protocol). This prophylaxis is also indicated for younger patients with a patient or family history of hypercoagulable states.

Psychosocial Support

The comatose child may hear any or all of the conversations held near the bedside. Therefore, all members of the healthcare team must avoid conversation and complex terminology that could be heard or misunderstood by the child, particularly discussions of a pessimistic prognosis.

At all times, the nurse should assume that the comatose child is able to hear and is frightened. Begin and end each shift by speaking gently to the child and orienting the child (if age-appropriate) to time and place. Throughout the day, talk to the child about the time of day and prepare the child before treatments or procedures are performed and before the child is moved. As the child is recovering, he or she may be awake yet unresponsive to surroundings and unable to ask questions; for such patients, a nurse’s daily support and review of the child’s progress (as appropriate) can be extremely helpful.

The family will require consistent information and support from the healthcare team to help them have a realistic understanding of the child’s prognosis. If the child’s recovery is doubtful, it will be necessary to prepare the family for the news, yet convey continued concern about the child’s care. The medical team must strike a fine balance to be realistic but avoid suggesting they have given up hope for recovery unless or until the child meets the legal definition of brain death. If withdrawal of support is considered, the family will be included in the decisions reached, but the pronouncement of brain death or futility and the recommendation of discontinuation of medical care will appropriately come from the medical providers (see Psychosocial Support of the Family in the Brain Death and Organ Donation section in this chapter).

Significant work has been completed in recent years to develop helpful tools to predict functional outcome after severe brain injury. These tools may be helpful in discussing long term outcomes with families.¹

As a rule, children demonstrate faster and more complete recovery from coma than do adults. However, it is important to note that the child’s brain is growing rapidly (particularly through the age of seven), making it extremely difficult to predict the degree of permanent neurologic damage that will result from a neurologic injury. Neurologic sequelae often are not manifest for months or years after the insult has occurred.¹ Recovery, too, can occur over years.

Support of Vital Functions

During status epilepticus, priorities of care include maintenance of systemic perfusion and cerebral oxygenation. During the seizure activity, place the child on a flat soft surface with no hard or sharp objects nearby. The patient’s bed is an appropriate surface, although the side rails should be padded. If the child is breathing spontaneously, position the child to prevent upper airway obstruction and to maximize diaphragm excursion. Place a roll under the child’s shoulders to extend the neck, and elevate the head of the bed approximately 30°.

In general, there is no need to stick anything in the patient’s mouth during seizures, particularly if the child’s aeration is adequate and if there is no obvious oral bleeding from lacerations of the mouth or tongue. In fact, forced insertion of a tongue blade or airway can cause broken teeth or oral lacerations. Placement of an oral airway is only recommended if tongue-biting or cheek-biting results in significant bleeding in the unconscious child.

If the child becomes apneic or demonstrates respiratory distress or inadequate aeration, provide bag-mask ventilation until intubation can be accomplished. Before endotracheal intubation is attempted, a nasogastric tube is inserted and suction is applied, and then the nasogastric tube is withdrawn. This procedure will allow emptying and decompression of the stomach to reduce the risk of vomiting during the intubation. It is extremely important that all members of the healthcare team be notified if neuromuscular blocking agents or sedatives are administered during the intubation, because these agents will affect or eliminate motor activity and neurologic responses after the intubation.

Throughout the episode of status epilepticus, carefully assess and support systemic perfusion. Treat hypotension or bradycardia promptly because they can result in inadequate systemic and cerebral perfusion (see Treatment of Shock in Chapter 6). If vascular access is not present, insert a large-bore venous catheter as quickly as possible to allow the infusion of IV fluids and medications. Obtain blood samples for analysis of arterial blood gases, electrolytes, glucose, calcium, and BUN, and to evaluate serum concentration of anticonvulsants, as indicated. If the child has just been admitted to the critical care unit, obtain a urine specimen for toxicology screening.

Perform a rapid neurologic examination to determine whether there is a reversible or accelerating neurologic problem responsible for the status epilepticus. Increased ICP, brain herniation, and intracranial hemorrhage can all produce seizures. If signs of intracranial hypertension are present, treat this problem at the same time that the status epilepticus is treated.

Rapid correction of any existing metabolic derangement is needed and may abolish the seizure activity. Because hypoglycemia is a relatively common and rapidly treatable cause of seizures in critically ill children, evaluate the serum glucose concentration, using point-of-care testing if available. Administration of hypertonic glucose (D₂₅:1.0-2.0   mL/kg or D₅₀:0.5-1.0   mL/kg), may be ordered empirically after blood samples are drawn, but before the results of serum electrolyte and glucose analyses are available. Hyponatremia, hypernatremia, hypocalcemia, or hypomagnesemia should be treated if present (see Chapter 12).¹¹⁹

Evaluate the infant’s rectal temperature, because febrile seizures are relatively common during infancy. If a high fever (body temperature >40° C) is present, administer an antipyretic suppository such as acetaminophen, and use a cooling blanket to slowly reduce the child’s temperature.

Anticonvulsant Therapy

The most popular drugs for the treatment of status epilepticus include lorazepam, diazepam, phenobarbital, and phenytoin or fosphenytoin. Each of these drugs is addressed separately in this section. The choice of drug will depend on provider preference and on the previous effectiveness of the drug for the patient. Intravenous, rather than intramuscular, drug administration is needed during status epilepticus to ensure maximal absorption and rapid CNS penetration.

If the child with a known seizure disorder presents with status epilepticus, it is important to ask the child’s parents or care providers about the child’s daily drug regimen and the last doses of anticonvulsants taken. In such patients determination of the serum concentration of anticonvulsants will assist in evaluation of the potential cause of and in treating the status epilepticus,

Any anticonvulsant agent can depress respiratory or cardiovascular function, so the bedside nurse plays a crucial role in assessing and supporting airway, oxygenation, ventilation, and perfusion as well as monitoring drug effect on seizures and neurologic function. In general, the patient requires intubation, mechanical ventilation, and establishment of hemodynamic monitoring. Volume expanders and vasoactive medications should be available at the bedside.

Lorazepam (Ativan) is the first-line treatment for all types of status epilepticus beyond the neonatal period.¹¹⁹ It has a rapid onset of action and stops seizure activity in most patients within 2 to 5   minutes.¹¹² Its effects last longer than those of diazepam; therefore, it may be preferable to diazepam. It is administered intravenously in a dose of 0.05 to 0.1   mg/kg (maximum single dose: 4   mg) over 2 to 5 minutes; the dose may be repeated in 10 to 15 minutes if needed. This drug may produce respiratory depression, although the incidence of this complication is lower than with diazepam. The nurse must be prepared to institute respiratory support if needed.

Diazepam (Valium) is used commonly in the initial treatment of seizures. The initial dose of 0.05 to 0.5   mg/kg (maximum: 5   mg for children under 5 years if age, and 10   mg for children over 5 years of age) is typically administered by slow IV push over several (3–5) minutes. The drug should be effective within minutes; peak diazepam concentrations are reached in the brain within 1 to 5   minutes. Because the serum half-life of the drug is relatively short, seizures often return and may require repeat dosing at 15-minute intervals. It is often necessary to add a second, longer acting anticonvulsant at this point.¹¹²

Side effects of diazepam include hypotension, cardiac arrest, laryngospasm, respiratory depression, respiratory arrest, sedation, and local vascular irritation at the site of infusion. Disadvantages of this drug are its relatively short effective period and the potentially significant respiratory depressant effects. One potential advantage of diazepam is that it is available in a formulation for rectal administration (Diastat) which may be used if the patient does not have intravenous access. This formulation is available in a pre-filled syringe (5   mg/mL). The dose for treatment of status epilepticus in infants and children 2 to 5 years of age is 0.5   mg/kg, for children 5 to 11 years of age the dose is 0.3   mg/kg, and for children over 12 years of age is 0.2   mg/kg.

Fosphenytoin (Cerebyx), the water soluble prodrug of phenytoin, is often used in the management of status epilepticus and is preferred to phenytoin because it is less caustic to the veins and is compatible with most IV fluids.¹²⁶ It is given as a loading dose of 10 to 20   mg phenytoin equivalents (PE) followed by a maintenance dose of 5 to 7   mg PE/kg per day in two to three divided doses. The therapeutic serum level is 10 to 20   mcg/mL. Side effects are similar to those of phenytoin and include hypotension, if the drug is administered too rapidly, bradycardia, tachycardia, and vasodilation.¹²⁰

Phenobarbital is used widely in the treatment of seizures in children, particularly infants, because it has a relatively long serum half-life and a wide therapeutic range. If phenobarbital is administered without diazepam, a loading dose of 10 to 20   mg/kg (given as a single dose or in divided doses; maximum total loading dose, 20   mg/kg) is administered intravenously at a rate no faster than 1   mg/kg per minute (or maximum rate, 50   mg/minute).^112,120

Phenobarbital is often administered with diazepam during the treatment of status epilepticus, because they seem to act synergistically. If phenobarbital is administered with diazepam, a lower phenobarbital dose (5.0   mg/kg; maximum dose, 390   mg) may be given initially by slow IV push. This dose usually is repeated twice (at 20-minute intervals), even if the seizures are controlled, to provide a total initial dose of 15.0   mg/kg and establish a therapeutic serum level (15-30   mcg/mL).

Peak concentrations of phenobarbital can develop in the brain within approximately 5   minutes, although the drug usually is not maximally effective for approximately 30   minutes. Side effects of phenobarbital include respiratory depression, bronchospasm, apnea, bradycardia, hypotension, and sedation. Occasionally, phenobarbital produces CNS irritability in children.¹²⁰ The major disadvantage of this drug is the long-term sedation it produces, making further neurologic evaluation difficult.

Valproic acid (valproate, Depakene) has long been used in the treatment of seizures refractory to first line agents. However, new information suggests that IV valproate may have a role in initial treatment of status epilepticus and may be as effective as phenytoin or fosphenytoin.^124,130 It is available in oral and IV formulations. A rectal formulation can be prepared by diluting valproate syrup (250   mg per 5   mL) with tap water in a 1:1 ratio.

An initial IV loading dose is 10-15   mg/kg per day divided into four doses (given every 6   hours for the IV formulation). The dose is then increased by 10 to 15   mg/kg per day on a weekly basis until a therapeutic level is obtained (50-100   mcg/mL). Generally a maintenance dose of 30 to 60   mg/kg per day is necessary to achieve therapeutic levels. Potential complications of this drug include the development of liver dysfunction (closely monitor liver enzyme concentrations), pancreatitis, and a possible increase in the plasma concentrations of other anticonvulsants.

Levetiracetam (Keppra) is used primarily for the treatment of partial onset seizures, but more recently it has been used in the treatment of status epilepticus refractory to first line agents.¹³⁰ The usual dose is 5 to 20   mg/kg per day divided into two doses per day, with weekly increases of 10   mg/kg per day to a maximum dose of 60   mg/kg per day. Dose recommendations for status epilepticus vary and firm recommendations do not currently exist; therefore, providers will need to titrate doses and closely monitor patient response.^124,130

Barbiturate Coma

If status epilepticus is unresponsive to the drugs listed previously, it may be necessary to transfer the patient to a facility where intensive and continuous hemodynamic and electroencephalographic monitoring can be performed. Control of status epilepticus may then be attempted by administration of barbiturates to induce coma.

Before coma is induced, providers must initiate adequate monitoring. The child is intubated and ventilated mechanically, an arterial line is inserted, and a central venous catheter is placed. Because high doses of barbiturates frequently produce hypotension, the child’s intravascular volume must be adequate and volume expanders must be available at the bedside. An infusion of an inotropic agent such as dopamine or epinephrine must also be available at the bedside for immediate use if hypotension develops.

Once adequate monitoring and support are established, phenobarbital or pentobarbital is administered in doses sufficient to induce coma. Thiopental sodium often is preferred because it has a shorter half-life, so that the effects will disappear in a shorter period of time following discontinuation of the drug. A loading dose is required, followed by a continuous infusion or hourly dose titrated to maintain burst suppression (associated with a reduced cerebral metabolic rate) on the EEG.¹²⁰ The child’s blood pressure and systemic perfusion must be monitored closely as the barbiturate dose is increased, and appropriate therapy must be provided to maintain systemic perfusion.

Table 11-10 includes a list of common anticonvulsant therapies for status epilepticus. Once the child’s seizures are controlled, long-term anticonvulsant prophylaxis and patient and family education is planned.¹¹²

Non-pharmacologic Management of Seizures

Several forms of ketogenic diets have been used for centuries to reduce seizures. These diets have gained in popularity in recent years, particularly for patients who are refractory to antiepileptic agents. The precise mechanism by which the diet inhibits seizures is unclear.¹³² The diet induces ketosis by providing most daily calories from fat sources, so the classic diet strictly limits carbohydrate and protein intake to minimum daily quantities. Recently, more liberal forms of the diet have emerged, allowing for slightly more protein and carbohydrate intake.

The goal of all forms of ketogenic diet is to control seizure activity through strict dietary control; such control may be challenging, particularly for toddler and adolescent patients. Seizure control is generally observed 1 to 3 months after initiation of the diet. The diet is continued for approximately 3 years if tolerated, and then it is gradually weaned. Side effects of the diet are primarily gastrointestinal in nature; the high fat intake can contribute to constipation and reflux. Patient growth is monitored closely, with assessment for micronutrient deficiencies and elevated serum lipids. During initiation of the diet, serum glucose concentrations are monitored on a frequent basis.

When a patient receiving the ketogenic diet is admitted to the critical care unit, care should be taken to preserve the ketotic state. This state requires either continuing the patient’s home dietary regimen or providing IV fluids and nutrition containing little protein and dextrose but high fat content. Medications must be evaluated because many oral solutions are provided in a high-glucose vehicle; these solutions are avoided if at all possible.

Vagal Nerve Stimulators

The vagal nerve stimulator may be implanted to control seizures in pediatric patients with medically and/or surgically refractory epilepsy. The precise mechanism by which vagal stimulation controls seizure activity is unknown. Stimulation of the afferent tract of the vagus nerve may desynchronize electroencephalographic activity and alter epileptic activity. Common side effects of vagal nerve stimulator insertion include hoarseness, shortness of breath, paresthesia, and cough. Infection of the generator pocket is also a concern in the immediate post operative period.

Wound care is similar to that needed following cardiac pacemaker implantation. In addition, electromagnetic and electrostimulation devices, including magnetic resonance imaging are avoided.^73,115

Surgical Interventions

Surgical intervention may be provided for intractable seizures. This seemingly radical approach has rendered many children free of seizures or has vastly improved their seizure control and quality of life. Preoperative testing including MRI, video electroencephalogram, and often subdural electrode placement (grids and strips) is necessary to define the seizure focus before surgical resection.

The surgical procedure is tailored to the location of the seizure focus, surrounding tissue, and goal of the surgery. For example, if the patient has a localized lesion that is amenable to resection, a targeted resection may render the patient completely seizure free. If the seizure focus is not resectable or diffuse in nature, a palliative procedure such as complete or partial hemispherectomy, corpus callosotomy, or multiple subpial transection may be performed. In these cases, seizure activity should be better controlled but will likely not be eliminated completely.

Care for these patients is similar to general postoperative neurosurgical critical care (see the Postoperative Care of the Pediatric Neurosurgical Patient, later in this chapter). Anticonvulsants are generally continued in the initial postoperative period and then gradually weaned as tolerated. The nursing care plan must include a description of the patient’s baseline seizure activity, the procedure performed, and any anticipated postoperative deficits.^94,95

Endocrinopathies Associated with Neurologic Insults

Diabetes insipidus (DI), the syndrome of inappropriate antidiuretic hormone (SIADH), and cerebral salt wasting (CSW) are common endocrine complications of neurologic injury or surgical procedures. CSW associated with head injury or neurosurgical procedures usually develops later (2-7 days) after injury. Please see Chapter 12 for a complete discussion of the pathophysiology, clinical presentation and management of these disorders. Table 12-7 compares and contrasts the presentation and effects of DI, SIADH, and CSW.

Irreversible Condition

The cause of the cessation of brain function must be irreversible. For example, devastating closed head injury or anoxic insult can be irreversible causes of brain death. Metabolic conditions such as hypotension, hypoglycemia, or hypothermia are reversible conditions and must be corrected if they are thought to be contributing to the depression of CNS function. In the past, sedative levels of barbiturates or narcotics could not be present because they could cause a reversible depression of brain function; in some institutions, if cerebral perfusion studies are used as an adjunctive test, barbiturates or narcotics may be detectable in serum samples, because they are not known to affect the results of cerebral perfusion studies.

Physical Examination to Document the Absence of Brainstem Function

The child must have no voluntary movement or response to stimuli in the absence of neuromuscular blockade. All brain stem function must be absent. The cranial nerve functions will be evaluated as possible through the testing of the following reflexes: oculocephalic, oculovestibular, cough and gag, corneal and pupil response to light. The pupils must be dilated or fixed in midposition, and apnea must be present. Flaccid paralysis must be present (Box 11-7).