Preoperative Evaluation and Questions: What is the indication for surgery? (Aneurysm, AVM, SAH, Tumor, Chiari) Pre-op Neurologic condition? Any deficits? Need for Neuromonitoring? Hunt-Hess Grade for Aneurysm? (I-V)
Risk: Mortality is based on Hunt-Hess grade: I =2%, II =5%, III =15-20%, IV =30-40%, V =50-80%. Morbidity: Hydrocephalus 15-20%, Neurogenic pulmonary edema (most common cause of non-neurogenic death) up to 20%. [Jaffe RA: Anesthesiologist’s Manual of Surgical Procedures, 4th ed. LWW: Baltimore, 2009]
Induction/Airway: Standard induction, ETT.
Lines and Monitors: Standard ASA plus Arterial line.
Mode of anesthesia: GA
Positioning: Prone or Sitting
Surgical Course: Induction, Intubation (controlled to avoid BP swings), a-line and additional IV placement, Head Pinning by surgeon (very painful, deepen Anesthesia just prior), Prone, Surgeons may place CSF drain, Significant blood loss possible from Scalp.
Intraoperative Goals and Events: Maintain CPP, (MAP – ICP) BP control (avoid hypo or hypertension, SBP 100-160) Lower ICP with Hyperventilation and Mannitol (also improves exposure for surgeons) Decrease CMRO2 (Barbituates, Volatiles, Propofol)
Duration: 3-6 hrs
Post-Operative Concerns, Transport, Disposition: to ICU post-op. Keep intubated if mental status questionable or to maintain hyperventilation. Can assess neuro exam post-op while intubated by titrating narcotics. Vasospasm: Risk highest 6-8days post-bleed, Treat w/ Triple-H therapy (Hypervolemia, Hypertension, Hypoviscosity) Mannitol Overdose (>1mg/kg = Hyponatremia, Hyperkalemia, Anemia)
Evidence-Based Medicine: Hyperventilation: Hypocapnia decreases ICP and improves surgical exposure through cerebral vasoconstriction. It is important to consider other systemic effects of hypocapnia. [Stocchetti N Chest. 2005 May;127(5):1812-27]
- ICP elevation
- Surgical Exposure
- Patient Positioning
- Venous Air Embolism (if sitting position)
- Quick awakening post-op to eval neurologic symptoms