The Power Spectrum Analyser as an Indicator of Cerebral Ischaemia during Carotid Endarterectomy

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Abstract
Stroke is a potential major compliction of carotid endarterectomy and may be caused by cerebral ischaemia or embolisation from the operative site. Conventional EEC monitoring has been used intraoperatively to identify periods of cerebral ischaemia, but this monitoring technique can be difficult to operate and interpret in the operating room. This study reports the use of a new signal analyser, the power spectrum analyser (PSA-1, Neurologics, Inc., Nashville, Tennessee), and its impact on active patient management. Thirty-six patients undergoing carotid endarterectomies were monitored with the PSA-1 in conjunction with routine EEG. Eight patients (22%) showed evidence of ischaemia 22 times on both PSA-1 and routine EEG. At no time did the routine EEG show evidence of ischaemia when the PSA-1 did not. The PSA-1 has proven to be a reliable neurophysiologic monitor for the identification of periods of cerebral ischaemia. Use of this small, easily operated and interpreted machine could enhance safety in operating rooms lacking sufficient resources to use conventional EEG machines.