Neurosurgical Emergencies

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Chapter 45 Neurosurgical Emergencies

Fred A. Fow, MD

1 What is the basic pathophysiology of increased intracranial pressure?

The theory is: The skull is a rigid compartment of fixed volume. Its three constituent parts are brain tissue, blood, and cerebrospinal fluid (CSF). Any increase in the volume of one of these constituents without a decrease in the volume of one or both of the other constituents must result in an increase in intracranial pressure (ICP) (modified Monro-Kelli hypothesis).

Greenes DS: Neurotrauma. In Fleisher GR, Ludwig S, Henretig F (eds): Textbook of Pediatric Emergency Medicine, 5th ed. Philadelphia, Lippincott Williams & Wilkins, 2006, pp 1361–1388.

2 How does increased ICP affect cellular survival?

Cellular survival depends on cerebral blood flow delivering oxygen to meet cellular metabolic demand. Cerebral blood flow is related to cerebral perfusion pressure. Cerebral perfusion pressure (CPP) in turn is affected by changes in mean arterial pressure (MAP) or intracranial pressure ICP (CPP = MAP − ICP). Cerebrovascular autoregulation (reflex vasoconstriction/vasodilatation) allows cerebral blood flow to be maintained despite changes in cerebral perfusion pressure. Autoregulation prevents decreases in cerebral blood flow while MAP is greater than 60 mmHg and while ICP is < 40 mmHg. Outside these ranges, cerebral blood flow and oxygen delivery drop in a passively dependent fashion, resulting in cellular injury.

Greenes DS: Neurotrauma. In Fleisher GR, Ludwig S, Henretig F (eds): Textbook of Pediatric Emergency Medicine, 5th ed. Philadelphia, Lippincott Williams & Wilkins, 2006, pp 1361–1388.

6 Describe the initial management of increased ICP.

Maintenance of airway, breathing, and circulation (ABCs) is paramount.

In the patient with suspected cervical spine trauma, immobilization is mandatory until cervical spine injury and spinal cord injury can be ruled out clinically and radiographically.

7 What are the relevant features of airway management in patients with increased ICP?

Endotracheal intubation allows for airway maintenance, protection from aspiration, maximal oxygenation, and control over ventilation. Rapid sequence induction (RSI) may help to prevent elevations in ICP and aspiration during intubation. The physician should be experienced in endotracheal intubation and have familiarity with RSI and with the specific indications and contraindications to the use of any of the agents used in RSI.

Hyperventilation causes cerebrovascular constriction, reducing cerebral blood volume and hence reducing ICP. Hyperventilation should be reserved for cases of impending herniation, as evidenced by severe alterations in mental status and vital signs changes or cases of increased ICP resistant to other modalities of treatment. Excessive or prolonged hyperventilation may result in cerebral ischemia and should be avoided.

8 Which medications are recommended in the treatment of increased ICP?

Mannitol may be used acutely to draw fluid from brain tissue in cases of impending herniation or cases of increased ICP resistant to other treatment modalities.

Hypertonic saline has been demonstrated to be an acceptable alternative to mannitol.

Dexamethasone acts more slowly, but may be employed to reduce tissue edema, such as that accompanying tumor, brain abscess, and nontraumatic hemorrhage.

Acetazolamide can be given to reduce CSF production but also has limited acute effect.

Adelson PD: Guidelines for the acute medical management of severe traumatic brain injury in infants, children and adolescents. Chapter 17. Critical pathway for the treatment of established intracranial hypertension in pediatric traumatic brain injury. Crit Care Med 4(3 Suppl):565–567, 2003.

Greenes DS: Neurotrauma. In Fleisher GR, Ludwig S, Henretig F (eds): Textbook of Pediatric Emergency Medicine, 5th ed. Philadelphia, Lippincott Williams & Wilkins, 2006, pp 1361–1388.

Steele DW: Neurosurgical emergencies, nontraumatic. In Fleisher GR, Ludwig S, Henretig F (eds): Textbook of Pediatric Emergency Medicine, 5th ed. Philadelphia, Lippincott Williams & Wilkins, 2006, pp 1717–1725.

9 What steps can be taken to reduce metabolic demand?

Adequate sedation helps to reduce oxygen demand and avoid any unwanted increases in ICP due to agitation.

Benzodiazepines, narcotics, and propofol should be used with caution because they may lower blood pressure and adversely affect cerebral perfusion pressure.

Barbiturate coma with pentobarbital reduces cerebral metabolic demand and ICP but requires aggressive pulmonary and hemodynamic management. As such, it is reserved for patients in whom other methods of ICP reduction have failed.

Paralysis may decrease oxygen consumption; however, this makes neurologic assessment, including recognition of seizures, problematic. Adequate sedation can obviate the need for paralysis. Avoidance of hyperthermia and of stimulation is also indicated.

Adelson PD: Guidelines for the acute medical management of severe traumatic brain injury in infants, children and adolescents. Chapter 17. Critical pathway for the treatment of established intracranial hypertension in pediatric traumatic brain injury. Crit Care Med 4(3 suppl):565–567, 2003.

Greenes DS: Neurotrauma. In Fleisher GR, Ludwig S, Henretig F (eds): Textbook of Pediatric Emergency Medicine, 5th ed. Philadelphia, Lippincott Williams & Wilkins, 2006, pp 1361–1388.

KEY POINTS: INCREASED INTRACRANIAL PRESSURE

1 The first and most important step in the treatment of increased ICP, regardless of its cause, is maintenance of the ABCs.

2 Rapid sequence induction and endotracheal intubation allow for airway protection and help prevent elevation of ICP during intubation.

3 Hyperventilation should be reserved for cases of impending herniation.

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