Medical Management of Adult and Pediatric Spinal Cord Injury

Published on 27/03/2015 by admin

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Chapter 70 Medical Management of Adult and Pediatric Spinal Cord Injury

The three primary goals of managing both adult and pediatric spinal cord injury (SCI) are to optimize neurologic outcome, provide for early mobilization, and facilitate rehabilitation. These goals are difficult to meet when medical complications supervene. Unfortunately, SCI patients are uniquely vulnerable to a variety of complications that, at a minimum, prolong hospitalization, increase costs, and delay entry into rehabilitation, and at the other extreme may impair neurologic recovery.

Fortunately, mortality after SCI is relatively low and continues to decline. However, morbidity, even in children, remains significant. Thus, attention to the medical management of SCI is essential, and the skills of a multidisciplinary team of spine surgeons, critical care specialists, and physiatrists are often required.

The American Association of Neurological Surgeons published guidelines in 2002 for the management of acute injuries of the cervical spine and spinal cord. This supplement includes medical management strategies for these challenging injuries.1

Pharmacologic Intervention

Administration of the steroid methylprednisolone within 8 hours of adult SCI has been shown from the National Acute Spinal Cord Injury Studies (NASCIS II and NASCIS III) to improve American Spinal Injury Association (ASIA) motor and sensory scores in patients.24 In response to SCI, the spinal cord swells, and methylprednisolone is administered to reduce inflammation in hope of preventing further nerve cell death. However, these NASCIS studies are controversial because they failed to address potentially important recovery-influencing details regarding surgical intervention and rehabilitative therapies.5,6 Furthermore, later analysis revealed that these studies did not demonstrate an improvement in patients’ primary outcome measures, which indicates that the improved recovery could be due to random events.58 Because these studies are not entirely credible, evidence is lacking to decisively recommend the use of methylprednisolone following acute SCI.

The studies, however, do demonstrate that it is inadvisable to use methylprednisolone more than 8 hours after SCI because it is associated with a slight decrease in neurologic recovery.4 Additionally, the NASCIS studies document conclusively that methylprednisolone has serious side effects, such as higher infection rates, respiratory complications, and gastrointestinal hemorrhage. Therefore, methylprednisolone has no benefit in a neurologically intact patient.

Trials with other neuroprotective agents such as the ganglioside GM1, gacyclidine, tirilazad, and naloxone have also failed to demonstrate conclusive effectiveness, and their use cannot be justifiably recommended due to their potential side effects.

Clinical trials involving a new nerve repair drug, BA210 (Cethrin), have been conducted to investigate its safety and effectiveness in restoring neurologic function following traumatic SCI. Cethrin is a recombinant protein that acts as a rho inhibitor to promote neuroregeneration and neuroprotection in the CNS. Rho proteins are involved in a key pathway that promotes apoptosis, and the inhibition of this pathway facilitates axon regeneration at the site of the injury. The clinical trials demonstrated that topical administration of 0.3, 1, 3, or 6 mg of Cethrin following surgical decompression is safe. Recently, a placebo controlled trial has been initiated in order to better assess the drug’s clinical efficacy.9

Pulmonary Considerations

The respiratory system is uniquely susceptible to SCI because primary neurologic dysfunction profoundly affects respiratory physiology directly, as well as indirectly. Cervical injury is more commonly associated with pulmonary complications, as 84% of all respiratory complications are the result of C1-4 injuries. However, more than 60% of patients with lower-level injuries develop pulmonary problems, so these may also occur from thoracic-level injuries.11 Pulmonary complications are the single most common cause of morbidity and mortality after pediatric SCI.

The muscles of respiration include the abdominal, intercostal, diaphragm, and cervical accessory muscles. The abdominal muscles are the primary muscles of active expiration and account for over 50% of expiratory capacity. Thus, thoracic SCI with abdominal muscle paralysis may lead to ineffective expiration, excessive end-tidal volumes, and, subsequently, a diminished lung capacity.12,13

To diagnose an abdominal injury in a patient with cervical SCI and hypotension, a Focused Assessment with Sonography for Trauma (FAST) abdominal ultrasound examination is recommended.14 FAST is a diagnostic tool used to screen for significant hemoperitoneum after blunt trauma.15 In the absence of or after a positive FAST examination, an abdominal CT scan is advisable to better define the nature of the injury. In a hemodynamically stable patient, a FAST examination is less reliable and the use of a CT scan is necessary to reduce the number of missed injuries.16

The intercostal muscles play an important role in stabilizing the chest wall during inspiration. Their paralysis results in a functionally flail chest, in which the chest wall collapses during inspiration and expands during expiration, resulting in an overall loss of tidal volume.

The diaphragm muscles account for approximately 50% to 60% of the inspiratory force generated. When the other muscles of respiration are nonfunctional, however, the diaphragm assumes 100% of the workload and may rapidly fatigue.17

Overall, generalized muscle weakness associated with midthoracic injury levels contributes to diminished contraction force for effective coughing and clearing of secretions. These muscle abnormalities, singly or in combination, may ultimately significantly decrease functional residual capacity, tidal volume, and inspiratory and expiratory volumes, while markedly increasing residual lung volumes.18 Nasotracheal suctioning is often insufficient to mobilize secretion, and consequently, expiratory aids such as mechanical insufflation-exsufflation or quad coughing are necessary.19,20

Remember that the vital capacity and the tidal volume of the quadriplegic patient are greater in the supine position than in the upright position. In the supine position, the weight of the abdominal contents helps in forcing the diaphragm rostrally, which leads to a decrease in residual volumes.21

Despite attention to these details, some patients may require intubation for respiratory support. The two primary indications are the inability to ventilate effectively (partial pressure of carbon dioxide >50 mm Hg) and the inability to oxygenate adequately (partial arterial oxygen pressure <80 mm Hg). It is critical to monitor these blood oxygen and carbon dioxide levels via pulse oximetry or arterial blood gas measurement early during SCI management.

Endotracheal intubation is often required before the location of an injury can be determined, so it is essential to keep the cervical spine as stationary as possible while securing the airway in case of a cervical-level injury. Succinylcholine is the recommended neuromuscular blocking agent to use during intubation, but only within the first 48 hours after injury due to the risk of hyperkalemia.22

Intubation with current endotracheal tubes can be safely maintained for several weeks, although there are some proponents of early tracheotomy. An early tracheotomy should be considered for any patient with high tetraplegia or one who is likely to remain ventilator dependent for an extended period of time, since the tracheotomy simplifies the ventilator weaning process. One review of tracheotomy in critically ill patients illustrated that early tracheotomy reduces the duration of both the stay in the ICU and time needed for mechanical ventilation.23 Although almost all surgery for acute SCI requires an endotracheal tube, one disadvantage of early tracheotomy is that it may interfere with anterior cervical surgery in those patients who require internal stabilization from such an approach.

Except for quadriplegics with injury at very high levels, most SCI patients can be weaned from ventilatory support during acute hospitalization. A limited number of studies have demonstrated that high tidal volume ventilation of 20 mL/kg or greater (except for patients with adult respiratory distress syndrome or acute lung injury) during rehabilitation reduces the time to ventilator weaning and improves the outcomes for atelectasis.24 The use of a progressive ventilator-free breathing T-piece protocol also reduces ventilator weaning time.25 Most patients can be successfully weaned when the vital capacity is greater than 1 L, maximal negative inspiratory force exceeds 30 cm H2O, and minute ventilation is less than 10 L.26

Despite attention to these details, atelectasis and ventilator-associated pneumonia are still common in the SCI population, and thus, constant vigilance is of utmost importance to diagnose and treat pneumonia rapidly. Preventative strategies that reduce the risk of ventilator-associated pneumonia include the maintenance of the patient in a semirecumbent position, the assessment of the patient’s readiness for accepted ventilator weaning protocols, and the use of an orotracheal route of intubation.2729 The use of prophylactic antibiotics is not encouraged, even in those patients who require prolonged intubation or tracheotomy. Routine use may increase the occurrence of antibiotic-resistant infection.12,30

Another potential pulmonary complication of SCI is sleep apnea. Automatic respiration is regulated by spinal cord tracts that lie in the rostral cervical spinal cord. If these pathways are significantly damaged, only voluntary respiration (which is dependent on consciousness) is possible, and breathing may cease during sleep. One should maintain a high index of suspicion of this syndrome in any patient with a high cervical SCI. An apnea monitor or pulse oximeter should be used on a continuous basis for 7 to 10 days after injury in such patients.

Hemodynamic Considerations

The transection of sympathetic pathways after SCI, with concomitant unopposed vagal activity or hyperactivity, accounts for the majority of cardiovascular complications associated with SCI.31 Monitoring with a Swan-Ganz catheter, however, has documented far-reaching hemodynamic derangements in these patients. The primary immediate concerns are generally bradycardia and neurogenic spinal shock. Although the majority of patients with cervical SCI have bradycardia, only rarely does this become of significant clinical concern to warrant treatment with atropine or use of a temporary transvenous cardiac pacer. Nevertheless, it is important to utilize electrocardiographic monitoring during the early phase after cervical SCI.32

In addition to electrocardiographic monitoring, it is necessary to monitor both the temperature and blood glucose level of an SCI patient. Temperature is a factor because the disruption of the autonomic nervous system can cause a loss of vasomotor control, which impairs the patient’s thermoregulation. Blood glucose levels are significant because insulin therapy may be needed to maintain normoglycemia in mechanically ventilated patients. A randomized study has shown that regulating blood glucose levels between 80 and 110 mg/dL reduced ICU mortality rates when compared with conventional treatments.33

The most important aspect of initial hemodynamic management is to prevent and treat hypotension, particularly in cases of high-level SCI where hypotension is most common. Treatment with early fluid resuscitation, while avoiding fluid overload, is employed to maintain tissue perfusion. Once intravascular volume is restored, vasopressors may be used to constrict the blood vessels to treat hypotension.34 Fluids and vasopressors are administered to maintain a mean arterial pressure of 85 mm Hg for up to 7 days, and the initial base deficit or lactate level may be useful when determining the need for ongoing fluid resuscitation.35,

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