📑
Chapter Summary
• Context: Anesthesia for spine surgery requires managing complex physiological interactions across varied patient profiles, surgical complexities, and operative positions. Prone positioning induces significant alterations in cardiac preload, ventilation-perfusion matching, intraocular pressure, and facial/extremity pressure points. High-complexity deformity, oncologic, or revision cases can involve massive blood loss, hypothermia, coagulopathy, and hemodynamic instability. Furthermore, intraoperative neurophysiological monitoring (IONM) imposes rigorous anesthetic constraints, precluding the continuous use of neuromuscular blocking agents and limiting volatile halogenated gases. Anesthetic management requires comprehensive preoperative evaluation, precise hemodynamic control to optimize spinal cord perfusion, multimodal analgesia, neuroprotective strategies, and close interdisciplinary communication.
• Chapter Objective: To present anesthetic principles for spine surgery, covering preoperative risk stratification, airway management in cervical instability, physiological effects and complications of prone positioning, total intravenous anesthesia (TIVA) for neuromonitoring compatibility, fluid management, blood conservation, and postoperative visual loss prevention.
• Preoperative Evaluation and Airway ManagementRisk stratification evaluates cardiopulmonary reserve, frailty, and prior spine surgery. Cervical instability and myelopathy require careful intubation to prevent neurological worsening; video laryngoscopy or awake fiberoptic intubation under manual in-line stabilization is indicated for unstable cervical pathology.
• Prone Position Physiology and ComplicationsProne positioning can impede venous return via inferior vena cava compression, increasing epidural venous pressure and surgical bleeding. Bolsters must support the thoracic wall and pelvic girdles while keeping the abdomen completely free. Facial and ocular protection prevents ischemic optic neuropathy and facial pressure ulcers. Extremity positioning must avoid brachial plexus and peripheral nerve stretch.
• Anesthesia and Neuromonitoring CompatibilityTotal Intravenous Anesthesia (TIVA) using propofol and remifentanil infusions is the gold standard when recording motor evoked potentials (MEPs). Volatile halogenated anesthetics (isoflurane, sevoflurane) suppress synaptic transmission in anterior horn cells in a dose-dependent fashion and must be minimized or avoided. Neuromuscular blocking agents are restricted to induction, ensuring intact muscle twitch responses during monitoring.
• Hemodynamics and Blood ManagementMaintaining mean arterial pressure (MAP > 80-85 mmHg) preserves spinal cord perfusion, especially during deformity correction or spinal cord decompression. Tranexamic acid infusions, cell salvage, restrictive transfusion triggers, and normothermia maintenance constitute key blood conservation strategies.
• Clinical Application: Anesthetic planning begins with reviewing cervical spine stability and imaging. In unstable cervical spines, awake fiberoptic or video-assisted intubation is performed without head extension. On flipping to prone, verify that the abdomen hangs freely without bolster pressure, eyes and nose are completely free from contact, and arms are positioned without brachial plexus traction. For surgeries utilizing MEPs, establish TIVA maintenance and avoid neuromuscular blockers after intubation. Maintain MAP targets to ensure adequate spinal cord perfusion.
