Preoperative Evaluation and Questions: Indication for surgery? (Degenerative Disk Disease, Scoliosis, Neoplasm, Spondylolisthesis)
Need for Neuromonitoring?
Which and How many Levels? Previous back surgery?
Anterior or Lateral Thoracic approach requiring one lung ventilation?
Baseline Hct? (type and cross w/ blood available)
Risk: Mortality: 0.5 – 3%
Morbidity: Nerve root injury, CSF leak, Massive Blood loss. [Jaffe RA: Anesthesiologist’s Manual of Surgical Procedures, 4th ed. LWW: Baltimore, 2009]
Induction/Airway: Depending on which approach will be first, may induce on transport stretcher (if posterior first) or OR table (if anterior first). Anterior is usually first.
Lines and Monitors: Standard ASA, A-line, Level of Consciousness monitor (BIS, Sed-line).
Mode of anesthesia: General Anesthesia. May need TIVA depending on Neuromonitoring requirements.
Positioning: Supine or Lateral then Prone.
Surgical Course: Induction on stretcher, a-line, large PIV, BIS, and foley placed, then transfer to Jackson table either supine or prone (head of Jackson table interferes with intubation). Anterior portion is usually first but coordinate plan with surgical team. May be done with assistance from a general surgeon for exposure. The surgeon may request a pulse-ox monitor for the foot to monitor compression of iliac artery. After initial stage patient is closed, undraped, flipped, re-prepped and re-draped. Lighten Anesthesia during times of little or no stimulation to avoid hypotension. During posterior exposure, keep up with blood loss. Most blood loss occurs during posterior portion due to epidural veins. Blood loss correlates with number of levels, and is also increase if patient has had spine surgery previously. Avoid Interference with Neuromonitoring. Monitoring is typically done only for the posterior portion. Surgeons may request paralysis to assist with exposure of both anterior and posterior portions. Volatile anesthetics, Nitrous Oxide, and Neuromuscular blockers interfere with monitoring. 1/2 Mac Volatile with Narcotic infusion can be used. Most important is not to vary the level of anesthesia once neuromonitoring has begun. At end of second stage surgeons may desire rapid awakening to facilitate neurologic assessment.
Intraoperative Goals and Events:
Positioning: Can be challenging to change from supine to prone. May transfer to stretcher then back onto OR table prone. Take the usual precautions necessary for prone position (eyes, nose, arms, breasts, genitals, etc). Be careful with monitors and lines during transition to prone position.
Excessive Blood loss: Determine allowable blood loss, monitor intra-op Hct with frequent blood gases, have cell saver available (if patient does not have cancer).
Neuromonitoring: Can likely use volatile and paralysis for exposure of anterior portion then change to TIVA w/ Propofol and Sufentanil.
EBL: greater than 1000ml, usually requires cell-saver or blood transfusion.
Duration: 6 – 10hrs
Emergence: If blood loss and resuscitation have been mild to moderate it is reasonable to extubate in the OR. If the patient has co-existing cardiac, pulmonary, or other significant disease, and blood loss/ resuscitation was excessive then consider keeping patient intubated until assessed and stable in ICU. If possible surgeons may appreciate rapid awakening for neurologic assessment of lower extremities.
Post-Operative Concerns, Transport, Disposition: Coordinate post-op plans with surgical team; usually ICU overnight.
Controlled Hypotension: Had been suggested as a means to reduce blood loss. [Yashon D, J Neurosurg. 1975 Nov;43(5):579-89] Is used much less frequently now because of concern for hypoperfusion as a result of hypotension.
Postop Blindness: [Myers MA, Spine 1997; 22:1325-1329] [Williams EL, Anesth Analg 1995; 80:1018-1029] Neuromonitoring: [Bala E, Anesthesiology. 2008 Sep;109(3):417-25]