招聘講演（14）

The Occasional Neuroanesthesiologist – The questions to ask to assure success

Adrian W Gelb

Professor Department of Anesthesia & Perioperative Care

University of California San Francisco

The preoperative work up of the neurosurgical patient obviously involves the “routine” history, physical and appropriate laboratory tests. However there are a few additional questions which will make planning the intraoperative care easier.

1) What’s the diagnosis and what operation will you do?

Acute subdural: These are usually associated with acute head trauma so that the underlying brain is also injured and ICP increased. Chronic subdural: The underlying brain is usually not injured. Once the hematoma has been removed, the brain should be allowed to fill the space i.e. P_aC0₂ should be normal or slightly elevated. Tumor: These usually present with elevated intracranial pressure and/or seizures. Anesthetic management is focused on preventing increases in ICP and preferably lowering it.

2) What position will the patient be in? Procedures are done in many different positions - Supine, Lateral, Modified Lateral (Park Bench), Prone, Sitting.

3) How much bleeding will there be? Performing a craniotomy i.e. “the opening” should usually result in <250 ml blood loss. Meningiomas, aneurysms and AVM’s all have the potential for great blood loss.

4) Do you anticipate any ischemia? This may be an indication for neuromonitoring and the surgeon may request some (unproven) neuroprotective drugs. In neurosurgery there are no prospective randomized trials showing a benefit to any of the commonly used techniques including drugs, shunts and physiological manipulation.

5) Will there be any neuromonitoring? Sensory and/or Motor Evoked Potential are used during intracranial, neurovascular and spinal procedures to prevent ischemic injury. Prospective randomized trials of all the neuromonitoring modalities are lacking.

6) Is the ICP elevated? Patients with acute coma producing elevated ICP or very large lesions will have exhausted compensatory mechanisms and will not tolerate further increase in ICP. Our recent multicenter trial found that hyperventilation (P_aCO₂ 28) improved operating conditions and ICP in patients with supratentorial tumors.

7) Where will the patient go afterwards? The disposition of the patient to the ICU or the PACU may influence the anesthetic choice.

References:

Gelb AW et al. Does hyperventilation improve operating condition during supratentorial craniotomy? A multicenter randomized crossover trial. Anesth Analg. 2008; 106:585-94

Patel P. No magic bullets: the ephemeral nature of anesthetic-mediated neuroprotection. Anesthesiology 2004;100:1049