EEG monitoring for induced hypotension for surgery of intracranial aneurysms.

Abstract

SUMMARY EEG was monitored at bilateral scalp sites outside the operative field during hypotensive aneurysm surgery in 21 patients. Mean arterial blood pressure at axillary level was 50-60 mm Hg (average 55 mm) for 1.9-5.3 hours (average 3.6). Four new deficits were noted immediately post-operatively, all related to the operated site: these were attributable to intra-operative rupture with forced vascular clipping, vasospasm, or edema. In no instance was hypotension solely responsible for a new deficit. EEG showed persistent slowing in relation to surgery in only 1 patient, where aneurysmal rupture led to severe hypotension, forced clipping of 1 posterior cerebral artery, and subsequent brain stem infarction. In the 3 other patients with fresh focal postoperative deficits, no persistent intraoperative EEG changes were observed. EEG monitoring did not detect ischemia in these 3 patients because 1) hypotension was moderate and did not perse cause new deficit, and 2) EEG electrodes did not survey the area at maximal risk, namely the operative field. EEG scalp electrodes near but outside the operative site do not seem useful for monitoring cerebral function in the region of aneurysm surgery. Epidural or cortical electrodes in the operative field may prove to be more useful.Stroke Vol 10, No 3, 1979RUPTURE OF an intracranial aneurysm during surgery remains a threat even in the era of microsurgery. Profound controlled hypotension reduces the risk of rupture and aids dissection. 1 Hypotension "defuses" the aneurysm by markedly decreasing wall tension. As one reduces cerebral perfusion pressure, however, the lower limit of autoregulation is approached, and risks of cerebral ischemia increase. This is particularly true when subarachnoid hemorrhage or surgical manipulation has already compromised autoregulation. Therefore, reliable techniques are needed for monitoring the CNS response to lowered blood pressure during aneurysm surgery.Since the electroencephalogram (EEG) continuously assesses certain aspects of electrophysiologic function of the brain, this test seemed potentially useful for monitoring hypotension during aneurysm surgery. EEG monitoring during carotid endarterectomy during cardiopulmonary bypass can likewise warn of cerebral ischemia during hypotension. In a series of 75 patients undergoing cardiopulmonary bypass, intraoperative EEG accurately predicted postoperative neuropsychiatric deficits and in several instances ischemic EEG changes were reversed by raising mean arterial blood pressure." Therefore, we have studied the clinical usefulness of intraoperative EEG as a monitor of the CNS response to induced hypotension during aneurysm surgery. Methods PatientsTwenty-one patients undergoing aneurysm surgery were studied. Characteristics of these patients are

Risks and benefits of deliberate hypotension in anaesthesia: a systematic review

“…None of them was considered to have a low risk of bias. The best current evidence showed that the heart rate may be increased or may remain stable during deliberate hypotension, depending on the drug used to induce hypotension 55,56, 66,69,79,91,154 . Similarly, the cardiac output may or may not change depending on the anaesthetic technique used.…”

“…Cerebral damage or neurological deficit 79,127 , stroke 90 , dysrhythmia 123 , cardiac arrest 111 or even death 111,127 following hypotensive anaesthesia have been reported. Most of these cases involved patients with pre-existing disease.…”

Use of computerized electroencephalographic monitoring during aneurysm surgery

“…Six of these eight patients awoke with new neurological deficits. In an earlier report, Jones,et al,6 using conventional eight-channel EEG monitoring during aneurysm surgery, were unable to demonstrate a similar association between persistent EEG abnormalities and new postoperative neurological deficits. In their investigations, the EEG monitor failed to identify intraoperative ischemia in three of the four patients with postoperative focal deficits.…”

“…'8 '25 Electroencephalographic (EEG) monitoring with conventional eight-to 16-channel apparatus is a reliable means of evaluating cerebral perfusion during carotid endarterectomy (CEA), 21' 24' 26 cardiopulmonary bypass procedures, 22 and controlled hypotension.~'6 Intraoperative EEG monitoring during aneurysm surgery has received little attention, however, primarily due to problems with electrode placement, particularly over the operative region. 6 Recent advances in electronic technology have simplified the use ofintraoperative EEG monitoring. Commercially available computerized monitors that process the EEG signal into a concise form utilizing fast-Fourier analysis have been developed to simplify the recognition and interpretation of EEG changes during anesthesia.…”

Monitoring Techniques for Prevention of Procedure-Related Ischemic Damage in Aneurysm Surgery

“…EEG and ECoG allow direct monitoring of cortical activity and indirect assessment of adequate cortical perfusion (119,130) in various intraoperative settings, such as during induced hypotension and temporary vessel occlusion (35,43,57,61,130). Cortical monitoring can be performed by scalp or direct cortical registration (which requires a wide cortical exposure) and can be performed as a passive registration of the cortical spontaneous electrical activity (EEG) or as the evaluation of transcortical stimulus transmission after active stimulation (delayed cortical response [DCR]).…”