Evoked potential monitoring in anaesthesia and analgesia

Abstract

SummaryElectrophysiological monitoring of selected neural pathways of the brain, brainstem, spinal cord and peripheral nervous system has become mandatory in some surgery of the nervous system where preventable neural injury can occur. Evoked potentials are relatively simple methods of testing the integrity of various aspects of the nervous system. This review covers the variety of evoked potentials that can be monitored and outlines the principles of their measurement. Their use in specific situations and how factors such as anaesthesia might affect them is presented.

Intraoperative neurophysiological monitoring for the anaesthetist

“…6 The effect is less marked than those seen with volatile agents. Therefore, to preserve neuronal function during INM, a combination of intravenous agents is often employed.…”

“…The drastic effect on VEPs renders this modality useless in the presence of halogenated agents. [4][5][6] Isoflurane has the most potent effect, and halothane the least. Some authors believe that sevoflurane and desflurane are as potent as isoflurane during a steady state.…”

“…4 They cause a dosedependent decrease in amplitude and increased latency. 6 Even at high doses (60 µg/kg), the use of fentanyl results in reproducible SSEPs, making it an ideal agent during INM. BAEPs remain resistant to fentanyl up to doses of 50 µg/kg.…”

“…6 SSEPs are intermediate in sensitivity and depend on the type of agents used. 5 MEPs are dependent on a functioning NMJ, and may be totally abolished during the use of NMAs.…”

“…The early brainstem waves (< 10 ms latency) are more resistant to drugs than the early and late cortical responses (> 100 ms). 6 The effect of specific anaesthetic agents…”