Haemodynamic responses to incision and sternotomy in relation to the auditory evoked potential and spontaneous EEG

Abstract

We investigated the effect of incision and sternotomy on the auditory evoked potential (AEP) and EEG, to try to predict a haemodynamic response to incision or sternotomy using the AEP and EEG in 41 patients undergoing cardiac surgery during propofol and alfentanil anaesthesia. The AEP and EEG were recorded before incision, between incision and sternotomy, and after sternotomy. Peak latencies and amplitudes of AEP peaks V, Na, Pa, Nb, Pb and Nc were determined. From the EEG the median, spectral edge and peak power frequencies, and percentages of delta, theta, alpha and beta power were calculated. Each patient was classified as responsive, equivocally responsive or unresponsive to incision or sternotomy based on increase in arterial pressure and heart rate on incision and sternotomy. Before incision, Nb and Pb latency and propofol concentration were higher for unresponsive patients but heart rate and median frequency before incision were lower. After sternotomy, Pa and Nb amplitude, peak power frequency and percentage alpha power were higher, and percentage theta power lower for responsive patients. Pa latency was higher after sternotomy for unresponsive patients. Using a combination of heart rate, arterial pressures and features derived from the AEP (all recorded before incision), the occurrence of a response to incision could be predicted in individual patients with a sensitivity of 85%, positive predictive accuracy of 63% and total accuracy of 72%. We conclude that AEP are more sensitive to pain stimuli than spectral features of the spontaneous EEG. In addition, the AEP may help in predicting inadequate anaesthesia.

Comparison of analgesic techniques for antler removal in halothane-anaesthetized red deer (Cervus elaphus): electroencephalographic responses

“…Recent studies investigating the EEG effects of noxious stimulation have identified that changes in mid‐range EEG frequencies – as typified by the F 50 – are specific for noxious stimulation in human beings, sheep and horses (De Beer et al. 1996; Morris et al.…”

Neurophysiological techniques to assess pain in animals

“…Some have identified de‐synchronization associated with nociceptive stimulation (Rampil & Matteo, 1987; Wilder‐Smith et al. , 1995; de Beer et al. , 1996; Schwender et al.…”

“…A large number of studies have been carried out to investigate the effect of a clinical nociceptive stimulus on the EEG of anaesthetized patients and have produced varying findings. Some have identified de-synchronization associated with nociceptive stimulation (Rampil & Matteo, 1987;Wilder-Smith et al, 1995;de Beer et al, 1996;Schwender et al, 1996).…”

Investigation of the EEG effects of intravenous lidocaine during halothane anaesthesia in ponies

“…The electroencephalogram (EEG) has been extensively investigated as a tool to monitor anaesthetic depth in human beings and has also been studied in horses (Rampil & Matteo 1987; White & Boyle 1989; Drummond et al. 1991; De Beer et al. 1996; Otto et al.…”

“…Changes in the EEG during noxious surgical stimulation have been identified in human beings (Rampil & Matteo 1987; Wilder‐Smith et al. 1995; De Beer et al. 1996; Schwender et al.…”