Benefits, Shortcomings, and Costs of EEG Monitoring

Abstract

A 5-year experience with 562 carotid endarterectomies, using electroencephalogram (EEG) monitoring and selective shunting, was reviewed. EEG changes occurred in 102 patients (18%). The frequency of EEG changes, as related to cerebral vascular symptoms, was as follows: transient ischemic attacks, seven per cent (19/259); completed strokes, 37% (36/98); vertebral basilar insufficiency, 24% (32/135); asymptomatic, 21% (15/71). Patients with contralateral carotid occlusion exhibited EEG changes in 37% (28/76) of operations. Fifteen patients suffered perioperative strokes (2.6%). Nine of the 15 were associated with a technical problem of either thrombosis of the internal carotid artery (five) or emboli (four). Technical problems were more common when shunts were used (five per cent) than when they were not (0.9%). Patients who suffered strokes prior to surgery were more at risk to develop a perioperative stroke (three per cent) than those not suffering prior strokes (0.3%). The EEG did not change in three patients who had lacunar infarcts prior to surgery and who awoke with a worsened deficit. Our series does not clearly establish the advantages of EEG monitoring, which is expensive (+375/patient) and may not detect ischemia in all areas of the brain. However, the use of shunts may introduce a risk of stroke due to technical error that is equal or greater than the risk of stroke due to hemodynamic ischemia. Since the need for protection is unpredictable by angiographic or clinical criteria, the benefit of EEG monitoring may be in reducing the incidence of shunting in those patients whose tracing remains normal after clamping. The decision to shunt, however, when there is electrical dysfunction after carotid clamping should be based not only on the EEG but also on the clinical signs and computed tomography (CT) scan. Our data does not show a net benefit in selective shunting unless the patient has sustained a stroke prior to surgery.

Prospective randomized trial of routine versus selective shunting in carotid endarterectomy based on stump pressure

“…This method is the most direct measure of cerebral ischemia. 16,[35][36][37] However, many patients may not be able to undergo carotid surgery under cervical block anesthesia secondary to patient (high level of anxiety) or surgeon preference.…”

“…EEG monitoring 22,24,25,35 and stump pressure measurements 11,18-21 are the most common modalities used to assess the need for shunting under general anesthesia. Several authorities have correlated EEG monitoring and stump pressure measurement in patients undergoing general anesthesia and in awake patients to determine the reliability of these methods in detecting cerebral ischemia and selecting shunting.…”

“…Several authorities have correlated EEG monitoring and stump pressure measurement in patients undergoing general anesthesia and in awake patients to determine the reliability of these methods in detecting cerebral ischemia and selecting shunting. 9,15,16,[35][36][37][38] Selective shunting according to EEG changes is associated with a need for shunting in 15% to 18% of patients. 9, 15 Calligaro and Dougherty 16 reported the correlation of carotid artery stump pressure and neurologic changes during 474 CEAs performed in awake patients and indicated if CEA had been performed under general anesthesia, shunts would have been placed in 29% of patients if a stump pressure of Ͻ50 mm Hg systolic had been used as the threshold for shunting, and about 15% would have been shunted had a stump pressure of Ͻ40 mm Hg systolic been used.…”

Multicenter retrospective review of results and complications of carotid endarterectomy in 1981.

“…Experienced surgeons adamantly support their position concerning their methods of arterial repair and thus an evaluation of these differences is difficult to achieve. 26 ' l4 -' 9 Among the major problems with any multicenter study are the variations in populations treated, the dedication of the correspondents and investigators, and the completeness of hospital records. Recognition of minor neurological deficits is often not the same from institution to institution and several community studies suggest minor complications are not always recorded.…”

Ionic Liquid Gel‐Assisted Electrodes for Long‐Term Cutaneous Recordings

“…[ 2 ] It is often combined with other electrodes placed on the skin to simultaneously or independently measure cardiac activity (electrocardiography) [ 3 ] or muscular response (electromyography [ 4 ] -electrooculography). [ 5 ] Despite their widespread use in the majority of electrophysiological diagnostic procedures, currently used cutaneous electrodes have some shortcomings, especially in long-term measurements: [ 6 ] Temporal stability is an important characteristic for diagnostic tools, and in many cases, cutaneous recordings need to be performed over several days. [ 7 ] Ag/AgCl electrodes, which are the current gold standard in cutaneous recordings, require a liquid electrolyte to decrease the electrode/skin impedance.…”