Spinal Cord Injury

Spinal Cord Injury

The cervical and thoracolumbar regions are most commonly affected by trauma, and appropriate radiographs should be taken. The patient must be log rolled and the entire spine examined for deformities or injuries. The rest of the back should also be examined at this point to exclude other injuries. Hypotension with bradycardia is unusual in hypovolemia but, if present, does not exclude hemorrhage, especially in elderly patients. It is, however, more likely to be due to spinal cord damage in a patient with a history suggestive of spinal injury. Fluid replacement should be guided by careful cardiovascular monitoring to prevent circulatory overload. Other indicators of cord damage are acute urinary retention, diaphragmatic respiration, priapism (persistent abnormal penile erection), lax anal sphincter and flaccid paralysis of the limbs.

Immobilization of Cervical Spine

Until spinal injuries can be excluded or "cleared" the spine must be immobilize and this can be achieved in a number of ways. Two methods are in common use, compromising between simplicity of application and effectiveness: these are semi-rigid collars and manual in-line stabilization (MILS) (Figure 6.1). Further stability is achieved by using sandbags or blocks on either side of the head, with two non-elastic self adhesive tapes strapped across the head and on to a rigid spinal board. Users should be aware of the disadvantages of semi-rigid collars.

During laryngoscopy MILS reduces cervical spine movement by up to 60%. An assistant squatting behind the patient applies MILS by placing his or her fingers on the mastoid processes and the thumbs on the temporoparietal area of the skull. The hands are then pressed against the spinal board and act to oppose movements of the head caused by the anesthetist. Axial traction should not be applied because of the risk of exacerbating cervical spinal injuries. Until the spine is "cleared" a log roll should be performed for any movement or transfer of the patient.

Clearing the Cervical Spine

The exclusion of spinal injuries or "clearance" requires the exclusion of both bony and ligament injuries, and ideally requires a combination of clinical assessment and radiological investigation. Clinical clearance includes no evidence of posterior cervical tenderness, "no history of intoxication", "an alert patient", "no focal neurological deficit" and "no painful distracting injuries". If all the criteria are fulfilled then the cervical spine can be cleared without the need for imaging. Clinical clearance of cervical spine injury is difficult or impossible in patients who are unconscious (due to sedation, anesthesia or head injury) or have distracting injuries to other parts of the body. Anesthetists should understand the principles of clearing the cervical spine, since a proportion of patients cannot be clinically cleared for several days and prolonged cervical spine immobilization (with its inherent risks) may be necessary.

Air Way Management

Patients may require airway instrumentation as an emergency (for airway obstruction, respiratory failure or as part of the management of a severe head injury) or later in their management as part of anesthesia for surgical management of other injuries.

The extent to which the injured cervical spine can be safely moved is unknown. Therefore the main aim during management of the airway, in patients with potential cervical spine injuries, is to cause the least amount of movement possible. All airway maneuvers will produce some degree of movement of the cervical spine, including jaw thrust, chin lift and insertion of oral pharyngeal airways.

Mask ventilation is known to produce more movement than direct laryngoscopy. The first choice in establishing a definitive airway in the polytrauma setting is direct laryngoscopy and oral intubation, significant movement occurs at the occipito-atlanto-axial joint. The laryngeal mask airway (LMA) and intubating laryngeal mask airway are both extremely useful in the failed or difficult intubation. The forces applied during insertion can cause posterior displacement of the cervical spine but the movement is less than that seen in direct laryngoscopy.

In the can't intubate, can't ventilate' scenario there should be early consideration of the surgical airway or cricothyroidotomy. These techniques can produce posterior displacement of the cervical spine but this should not prevent the use of this life-saving procedure.

Spinal Cord Injury

Spinal cord injury results in important pathophysiological consequences in various systems of the body that require appropriate treatment.

Respiratory failure is common and pulmonary complications are the leading cause of death. The diaphragm (C3-C5) and intercostals (T1-T11) are the main inspiratory muscles. Expiration is a passive process but forced expiration requires the abdominal musculature (T6-T12). The abdominal muscles are therefore important for coughing and clearing respiratory secretions. The severity of respiratory failure depends on the level and completeness of the injury. Complete dissection of the spinal cord above C3 will cause apnoea and death unless the patient receives immediate ventilatory support. For lesions between C3 to C5 the degree of respiratory failure is variable and the vital capacity can be reduced to 15% of normal. These patients are at risk of increasing diaphragmatic fatigue due to slowly progressive ascending injury resulting from cord edema. This commonly results in retention of secretions and decompensation around day 4 post-injury, and intubation and ventilation is required.

Cardiovascular instability is particularly seen with high cervical cord injuries. At the time of injury there is an initial brief period of increased sympathetic activity resulting in hypertension and arrhythmias. This is followed by a more sustained period of neurogenic shock, resulting from loss of sympathetic outflow from the spinal cord, which may last up to eight weeks. This is characterized by vasodilatation and bradycardia and tends to be seen only in lesions above T6. Bradycardia is caused by loss of cardiac sympathetic afferents and unopposed vagal activity and may lead to asystole. This can be treated with atropine. Hypotension is due to the loss of peripheral vasoconstriction. The loss of sympathetic innervation to the heart means that increases in cardiac output are primarily achieved by increases in stroke volume. The initial treatment of hypotension involves intravenous fluid administration. Once preload responsiveness is lost, (i.e. the stroke volume cannot be increased further), then vasopressors will need to be commenced using either dopamine or norepinephrine, which are both - and 2-receptor agonists, thereby providing vasoconstriction, chronotropic and inotropic support to the heart.

The end-point of resuscitation is controversial. There is evidence that ongoing ischemia and secondary spinal cord damage is successfully treated by raising the mean arterial pressure to 85mmHg for up to seven days.

The symptoms may start weeks to years following the spinal injury and include paroxysmal hypertension, headaches and bradycardia. Below the lesion cutaneous vasoconstriction and bladder spasm may be seen. Above the lesion there may be flushing, sweating, nasal and conjunctival congestion. The patient may complain of blurred vision and nausea. If left untreated, complications include stroke, encephalopathy, seizures, myocardial infarction, arrhythmias and death. The condition can be triggered by various stimuli including surgery, bladder distension, bowel distension and cutaneous stimuli. Severe signs are seen with higher lesions, and it is rarely seen in patients with cord lesions below T10.

Management options include removal and avoidance of triggers such as the insertion of a urinary catheter. If surgery is planned, consider the use of spinal anesthesia as this reliably prevents the symptom complex. Other options include increased depth of anesthesia and vasodilators for the treatment of hypertension.