Spine surgery is performed for a variety of conditions including scoliosis, malignancy, herniated disks, degenerative spine disease, and spinal stenosis. The scope of surgical techniques range from quick minimally invasive single-level procedures to prolonged operations involving multiple spinal levels with potential for fluid shifts.
Anesthesia for spine surgery presents a number of challenges and demands a unique set of skills for the anesthesiologist. Patient comorbidities can include cardiovascular and respiratory impairment, airway management may be difficult, blood loss may be significant, and postoperative pain control can be challenging. Anesthetic management includes providing optimal surgical conditions, minimizing blood loss, ensuring adequate perfusion of the spinal cord, and supporting intraoperative neurological monitoring techniques.
Preoperatively, the airway must be evaluated with special attention to cervical spine instability and distorted anatomy. Respiratory function may be affected by spinal deformities, necessitating pulmonary function testing and arterial blood gas analysis, and pulmonary hypertension may result from severe kyphoscoliosis. Sensorimotor deficits should be elicited and documented. Blood count and coagulation factors should be checked, and blood should be ordered in advance.
Choice of anesthetic technique is affected by the type of monitoring necessary for the surgery. Intraoperative neurophysiologic monitoring often includes evoked potentials requiring total intravenous anesthesia (TIVA) with avoidance of volatile anesthetics and neuromuscular blockade. TIVA can be done with propofol and remifentanil infusions. Intravenous access should include at least two large bore catheters, and fluids should be warmed. An arterial catheter should be considered for continuous blood pressure monitoring and frequent blood draws. Central lines may be needed for vasoactive medication administration. Awake intubation with a fiberoptic scope may be needed. Induction and intubation are usually performed on the stretcher, and then the patient is flipped onto the operating table. During positioning, the endotracheal tube must be secured and position confirmed. Prone positioning necessitates careful attention to avoid pressure points to avoid optic injury and neuropathies, and a bite block is essential to avoid tongue and lip damage.
Major spine surgery comes with many potential complications. Potential for major blood loss should be considered, and the surgeon may request the use of antifibrinolytic agents and controlled hypotension to limit blood loss. The anesthesiologist must consider the potential for spinal cord ischemia when maintaining blood pressure goals. Ischemic optic neuropathy can cause visual loss, a rare but devastating event. Postoperative care may include keeping the patient intubated due to concern for airway edema from fluid shifts, necessitating intensive care.