Incidence and Background
The incidence of cervical spine injury is only 1-3% in adult head trauma, and 0.5% in children, however because of the prevalence of trauma, there are 10,000 SCI per year, 3500 of which lead to complete neurologic deficit. Most common locations for SCI are lower cervical or upper lumber, areas of high stress (because of their proximity to the rigid thoracic spine).
Mechanism of injury
There are four main mechanisms of injury in SCI – distraction, compression, torsion, and penetration. As in TBI, primary injury is unavoidable, but secondary injury can occur at the scene through extraction (especially in MVA) or intubation in the field.
The initial focus should be on oxygen delivery (avoidance of hypotension and hypoxemia), while assessing the patient for other injuries – note that the optimal time period on which to surgically correct SCI has not been determined, thus it is reasonable to manage these patients medically until their other injuries have been fully addressed.
Airway and Ventilation
If intubation is required in the hospital setting, succinylcholine may be safely used within 24 hours of injury [Cooperman LH JAMA 213: 1867, 1970], but should be avoided afterwards. Fiberoptic bronchoscopy should be strongly considered, although there is no data suggesting that it is superior to direct laryngoscopy with in-line stabilization.
Despite the fact that the phrenic nerve may be partially intact, C4 to C7 lesions still require ventilatory support because of lost chest wall innervation, paradoxical respiratory motion, and an inability to clear secretions.
Importantly, the patients may present with significant hypotension due to neurogenic shock (combination of low SVR with minimal cardiac ionotropy, distinct from other forms of shock in that the patient is bradycardic), but hemorrhage must still be ruled out as may of these patients have suffered polytrauma. Once hemorrhage has been ruled out or controlled, the focus should be on delivery of oxygen to the spinal cord. There are no well-defined MAP goals for SCI, however most authorities recommend “normal to high” levels and many practitioners strive for a MAP of 85 mm Hg – this is not, however, based on prospective or randomized data and is in fact controversial. [AANS. Neurosurgery 50 (3S): S58, 2002]
Steroids (The Controversy)
Many practitioners will administer methylprednisolone @ 30 mg/kg followed by a 5.4 mg/kg/hr infusion – this is based on data from the NASCIS II and III trials [Bracken MB et al. NEJM 322: 1405, 1990; Bracken MB et al. JAMA 277: 1597, 1997], both of which are highly controversial [Hurlbert RJ et al. J Neurosurg 93: 1, 2000; Short DJ et al. Spinal Cord 38: 173, 2000; Matsumoto T et al. Spine 26: 426, 2001] – an exhaustive critique of Bracken’s methodology was written by Coleman et al. [Coleman WP et al. J Spinal Disord 13: 185, 2000] which point out, among other things, that the primary outcome was negative (only in secondary, subgroup analysis were positive findings found), that the original authors tailored their statistical methods to achieve predetermined results, and that the placebo group treated before 8 hours did significantly worse than the placebo group treated after 8 hours (i.e. the control group was particularly weak). Other criticisms include that survival and quality of life were unchanged, and that the results of the NASCIS studies have not been reproduced in other studies.
Intraoperative anesthetic concerns are the same as on admission and in the intensive care setting, predominantly airway and hemodynamic management (complicated by spinal shock).
If the airway is not secure, caution should be used in intubating the trachea (consider an awake fiberoptic intubation – nasal is easier anatomically but may lead to sinusitis post-operatively. Oral intubation is more difficult but ideal if the patient will remain intubated).
An arterial line is mandatory, as 1) many SCI patients will be in spinal shock and 2) bone graft harvests, as well as thoracic and lumbar fractures can lead to significant blood loss, especially if corpectomy(ies) is(are) planned.
Suicide rates in spinal cord injury patients are 10x their age-matched peers. [Mil Med 162: 141, 1997]
Often these patients will have concomitant head injuries or decreased level of consciousness, which should significantly lower the threshold for intubation. Always beware of neck manipulation and gastric aspiration – consider using local anesthesia followed by fiberoptic intubation or rapid sequence intubation (neither is associated with more or less neck manipulation or risk of neurologic injury [Can J Anaesth 39: 114, 1992; Can J Anaesth 38: 785, 1991]). Succinylcholine must be avoided in SCI, as it has the potential to cause massive potassium release [Anesthesiology 32: 161, 1970; Anesthesiology 33: 558, 1970; Anesthesiology 32: 169, 1970], an effect which may last as long as 6 months.
Loss of intercostal muscles (T1-12) and abdominal muscles (T7-L1) can lead to reductions in total lung capacity of 25%, and of vital capacity by 55%. Paradoxical abdominal movement is common and represents diaphragmatic dysfunction. Other complications of SCI include inadequate cough, and diminished lung volumes due to abdominal contents. Consider intubating these patients when PO2 < 55 mm Hg on 50% O2, PCO2 > 45 mm Hg, RR > 35, or vital capacity < 10-15 cc/kg [Neurol Clin 9: 779, 1991]. High cervical SCI should be considered for early tracheostomy. Lower cervical SCI will often not require intubation (and thus tracheostomy) but still have a higher incidence of pneumonia.
When To Consider Intubating the SCI Patient [Andrews]
- PO2 < 55 mm Hg on 50% O2
- PCO2 > 45 mm Hg
- RR > 35
- Vital capacity < 10-15 cc/kg [Neurol Clin 9: 779, 1991]
Vital capacity will start to improve by 3-5 days, with rapid improvement over the first month and more gradual improvement for the next six months as the chest transitions for flaccid to spastic.
Pulmonary complications are the second most common cause of death in SCI patients (after the SCI itself). 44% of SCI will go into pulmonary edema after resuscitation from spinal shock [J Neurosurg 34: 168, 1971] – treat with intubation, toilet, and diuresis. Pulmonary embolism is another frequent cause of death in these patients – the incidence of DVT and PEs is 15 and 5%, respectively [Paraplegia 29: 8, 1991] and this risk continues up to 3 months after injury, despite rehabilitation [Paraplegia 31: 506, 1993; Arch PMR 75: 965, 1994; J Am Para Soc 16: 153, 1993]. For this reason, the American College of Chest Physicians has recommended LMWH on all acute SCI patients [Chest 114: S542, 1998]. Lastly, 5-20% of SCI will develop pneumonia.
Criteria to Attempt Weaning the SCI Patient [Andrews]
- TV > 5 cc/kg
- Vital capacity > 10 cc/kg
- RR < 30/min
- Peak inspiratory pressures > 20 cm H2O
An abundance of laboratory data suggests that elevating blood pressure improves blood flood to the spinal cord [Surg Neurol 10 71: 1978; Surg Neurol 10: 64, 1978; Surg Neurol 10: 63, 1978; J Trauma 28: 481, 1988], but so far no study has demonstrated benefit in human subjects. It is, however, generally accepted that SBP should be kept > 90 mm Hg.
Early on, SCI patients should receive an NG tube due to aspiration/gastric atony [Spine 6: 538, 1981]. Additionally, these patients require stress ulcer prophylaxis – there are no trials which show a significant difference in outcomes between PPI and H2 blockers in this population.
Initially after SCI, the bladder is hypotonic. Lesions proximal to the sacral cord ultimately produce a hypertonic bladder. Poor coordination between the detrussor muscle and the urinary sphincter results in incomplete emptying and progressively increasing urinary volumes.
SCI patients can develop pressure ulcers in less than 6 hours on a rigid spine board. [Arch PMR 74: 248, 1993; Arch PMR 81: 506. 2000]