What monitoring is indicated for patients undergoing craniotomy for clipping of intracranial aneurysm?

What monitoring is indicated for patients undergoing craniotomy for clipping of intracranial aneurysm?

In addition to routine monitoring for general anesthe-sia, aneurysm patients should have intra-arterial measure-ment of blood pressure. Most will agree that the intra-arterial catheter is best inserted prior to anesthetic induction, as hypertension associated with laryngoscopy increases the risk of rupture. A urinary catheter is also indicated as in all craniotomies. Central venous pressure monitoring may be helpful in assessing fluid status, espe-cially if mannitol is administered.

Many centers use electrophysiologic monitoring for aneurysm surgery when temporary arterial occlusion is anticipated during surgical dissection of the aneurysm. In these cases, arterial branches feeding the aneurysm may be temporarily occluded with surgical clips to reduce the risk of rupture. However, temporary arterial occlusion may lead to cerebral ischemia. This ischemic risk depends on the duration of arterial occlusion, collateral cerebral circu-lation, and brain temperature. Electroencephalogram (EEG) electrodes may be placed directly on the cerebral cortex over regions supplied by the arteries in question. Routine scalp electrodes for EEG may also be placed. In some centers somatosensory evoked potentials are moni-tored for detection of ischemia. Motor evoked potentials are highly sensitive to ischemia, but are probably still inves-tigational for aneurysm surgery. Although hypothermia is believed to improve the safety of temporary arterial occlu-sion in these patients, a recent large randomized trial of mild hypothermia for aneurysm surgery demonstrated no clinical benefit over normothermia.