Effects of surgical stimulation on midlatency auditory evoked potentials during general anaesthesia with propofol/fentanyl, isoflurane/fentanyl and flunitrazepam/fentanyl

Abstract

SummaryDuring general anaesthesia, niidlatencj-auditor?. evoked The midlatency auditory evoked potentials (MLAEP) occur 10 to 100 ms after stimulus presentation and are generated by different overlapping areas of the primary auditory cortex [l-61. The early auditory evoked potentials, generated in the brainstem, are grossly unchanged by anaesthesia [7-91. The late cortical components show a great variation of latencies and amplitudes in the awake state [l, 101. In contrast. midlatency peaks of the AEP do not differ intra-and interindividually. Under general anaesthesia with a number of general anaesthetic agents MLAEP are suppressed dosedependently [7][8][9][11][12][13]. . During general anaesthesia amplitudes of the early cortical waves of the AEP increased after surgical stimulation, indicating that MLAEP reflect the activity of the central nervous system and not only anaesthetic concentration. These observations were made during light anaesthesia with nitrous oxide and halothane. This raises the question whether surgical stimuli also lead to increases in MLAEP amplitudes when analgesia is provided during surgery by high dose opioids. Therefore, we investigated the effects of strong surgical stimuli, skin incision and steronotomy, on MLAEP in

Current status of perioperative hypnotics, role of benzodiazepines, and the case for remimazolam: a narrative review

“…99 In patients undergoing cardiac surgery, evoked potentials were preserved in those anaesthetised with flunitrazepam and fentanyl, whereas they were abolished when anaesthesia was maintained with isoflurane or propofol. 100 When a combination of midazolam and alfentanil was used to anaesthetise women for major gynaecological surgery, there was a high level of responsiveness (72%), as determined by the isolated forearm technique, and 3/32 had some recall of intraoperative events. 101 Midazolam produces a moderate depression of the bispectral index (BIS).…”

New drugs and technologies, intravenous anaesthesia is on the move (again)

“…48 49 In contrast, patients 'anaesthetized' with flunitrazepam and fentanyl showed minimal changes in the AEP, despite being apparently unconscious. 50 Perhaps, patients anaesthetized with a benzodiazepine/opioid combination are in some way aware but amnesic because of the interference by benzodiazepines with the formation of new memories? Certainly, when 'anaesthesia' was maintained with a combination of midazolam and alfentanil, and consciousness monitored by the isolated forearm technique, 72% of 32 patients responded with purposeful movements to verbal commands during surgery, but none had spontaneous, unprompted postoperative recall for the event.…”

Monitoring and control of unconsciousness during clinical surgery: Auditory evoked potentials (AEP) versus the clinical gold standard (CGS)

“…A pathfinder electrodiagnostic system has been used to record AEP signals using a 0.1 ms click duration at a frequency of 6.122 Hz. A study carried out by Schwender et al [27] measured the latencies of the peaks Na, Pa, Nb, and Pb (ms) and amplitudes Na/Pa, Pa/Nb, and Nb/Pb ( V). The AEP signals were recorded for awake and anaesthetized patients.…”