Surgery on the spine and spinal cord is undertaken for a variety of conditions, including intervertebral disk disease, spondylosis, stenosis, neoplasm, scoliosis, and trauma. The physiology of the spinal cord and brain is similar, even though absolute rates of blood flow and metabolism are lower in the spinal cord. Maintaining spinal cord perfusion pressure (which equals MAP minus extrinsic pressure on the cord) and reducing cord compression are clinical management objectives.
The prone position is frequently used. Most patients can be anesthetized on a stretcher and “logrolled” onto the operating room table after endotracheal intubation. Awake intubation should be considered for patients with tenuous neurologic conditions that may be worsened by laryngoscopy/intubation or positioning (e.g., patients with unstable cervical or thoracic spine injuries). Under these circumstances, an abbreviated neurologic examination should be performed after intubation and transfer to ensure that injury has not occurred. The anesthetist should ensure that all pressure points are padded; neck and extremities are in neutral positions; eyes, ears, nose, and genitalia are free from pressure; and all monitors and lines are secured in place and functioning. Special attention should be paid to the endotracheal tube, since it can move or kink in the process of positioning. Ischemic optic neuropathy is a potential complication of prone cases associated with length of procedure (usually >5 hours), blood loss (usually >2 L), hypotension, and fluid resuscitation. Increased facial swelling may alter venous hemodynamics in the globe, leading to optic nerve ischemia and postoperative visual deficits. There are no standard preventive guidelines, but maintenance of systemic blood pressure near baseline values, frequent eye checks to assess for direct pressure on the globe, and maintenance of adequate perfusion are likely beneficial.
Surgery to correct scoliosis can be accompanied by significant blood loss. Various techniques can be used to reduce homologous blood transfusion, including preoperative autologous donation, intraoperative hemodilution, use of intraoperative blood-scavenging techniques, and meticulous patient positioning to prevent increased abdominal and intrathoracic pressures that can increase venous bleeding. Because of concern of neurologic sequelae, induced hypotension may not be advantageous in this procedure. Scoliosis surgery is accompanied by a 1% to 4% incidence of serious postoperative neurologic complications. Spinal instrumentation and distraction can cause spinal cord ischemia and result in paraplegia. Intraoperative monitoring of spinal cord function is used routinely.
After acute spinal cord injury, surgery may be required to decompress and stabilize the spinal cord. The primary goal in the initial management of acute spinal cord injury is to prevent secondary damage to the injured cord. This is accomplished by stabilizing the spine and correcting circulatory and ventilatory abnormalities that can exacerbate the primary injury. The presence of cervical cord injury should lead one to suspect associated head, face, or tracheal trauma; thoracic and lumbar spine injuries often are associated with chest or intra-abdominal trauma.
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