Darren F Hight1, Amy L Gaskell2, Matthias Kreuzer3, Logan J Voss4, Paul S García5, Jamie W Sleigh6. 1. Department of Anaesthesia, Waikato Clinical School, University of Auckland, Hamilton, New Zealand; Waikato District Health Board, Hamilton, New Zealand; Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland. 2. Department of Anaesthesia, Waikato Clinical School, University of Auckland, Hamilton, New Zealand; Waikato District Health Board, Hamilton, New Zealand. 3. Department of Anesthesiology, Emory University School of Medicine, Atlanta, GA, USA; Anesthesiology and Research Divisions, Atlanta VA Medical Center, Atlanta, GA, USA; Department of Anesthesiology and Intensive Care, Technical University of Munich, Munich, Germany. 4. Waikato District Health Board, Hamilton, New Zealand. 5. Department of Anesthesiology, Emory University School of Medicine, Atlanta, GA, USA; Anesthesiology and Research Divisions, Atlanta VA Medical Center, Atlanta, GA, USA; Department of Anesthesiology, Columbia University, New York, NY, USA. 6. Department of Anaesthesia, Waikato Clinical School, University of Auckland, Hamilton, New Zealand; Waikato District Health Board, Hamilton, New Zealand. Electronic address: Jamie.Sleigh@waikatodhb.health.nz.
Abstract
BACKGROUND: EEG activity in the extended alpha frequency range (7-17 Hz) during maintenance of general anaesthesia is primarily determined by effect-site concentrations of the hypnotic and analgesic drugs used. Intermittent alpha loss during surgery, unexplained by changes in anaesthetic or opioid concentrations, could represent arousal of the cortex as a result of increased surgical stimulation. METHODS: A generalised linear model was fitted to alpha power recorded from patients undergoing general anaesthesia from induction until waking using three explanatory variables: age-adjusted volatile anaesthetic effect-site concentration, and estimated effect-site propofol and opioid concentrations. Model residuals were decomposed into uncorrelated white noise and a fluctuating auto-correlated trend. Deviations of this local trend were classified as 'unexpected alpha dropout events'. To investigate whether these alpha dropouts might be explained by the effect of noxious stimulation, we related their occurrence to whether a patient was undergoing surgery involving the body cavity or not. RESULTS: Alpha power dropouts occurred in 73 of the 237 patients included in the final analysis (31%, median amplitude of -3.5 dB, duration=103 s). They showed a bimodal or broadly skewed distribution, being more probable soon after initial incision (32%), dropping to around 10% at 1 h, and then again increasing to >30% in operations lasting >3 h. Multivariate analysis showed that alpha dropouts were significantly associated with body cavity surgery (P=0.003) and with longer operations (P<0.001). CONCLUSIONS: A loss of alpha power, unexplained by changes in anaesthetic or opioid concentrations, is suggestive of thalamocortical depolarisation induced by body cavity noxious stimuli, and could provide a measure of nociception during surgery.
BACKGROUND: EEG activity in the extended alpha frequency range (7-17 Hz) during maintenance of general anaesthesia is primarily determined by effect-site concentrations of the hypnotic and analgesic drugs used. Intermittent alpha loss during surgery, unexplained by changes in anaesthetic or opioid concentrations, could represent arousal of the cortex as a result of increased surgical stimulation. METHODS: A generalised linear model was fitted to alpha power recorded from patients undergoing general anaesthesia from induction until waking using three explanatory variables: age-adjusted volatile anaesthetic effect-site concentration, and estimated effect-site propofol and opioid concentrations. Model residuals were decomposed into uncorrelated white noise and a fluctuating auto-correlated trend. Deviations of this local trend were classified as 'unexpected alpha dropout events'. To investigate whether these alpha dropouts might be explained by the effect of noxious stimulation, we related their occurrence to whether a patient was undergoing surgery involving the body cavity or not. RESULTS: Alpha power dropouts occurred in 73 of the 237 patients included in the final analysis (31%, median amplitude of -3.5 dB, duration=103 s). They showed a bimodal or broadly skewed distribution, being more probable soon after initial incision (32%), dropping to around 10% at 1 h, and then again increasing to >30% in operations lasting >3 h. Multivariate analysis showed that alpha dropouts were significantly associated with body cavity surgery (P=0.003) and with longer operations (P<0.001). CONCLUSIONS: A loss of alpha power, unexplained by changes in anaesthetic or opioid concentrations, is suggestive of thalamocortical depolarisation induced by body cavity noxious stimuli, and could provide a measure of nociception during surgery.
Authors: Pradyumna B Suresha; Chad J Robichaux; Tuan Z Cassim; Paul S García; Gari D Clifford Journal: Anesth Analg Date: 2022-02-01 Impact factor: 6.627
Authors: Andrew J Michalak; Anil Mendiratta; Andrey Eliseyev; Brian Ramnath; Jane Chung; Jarret Rasnow; Lawrence Reid; Steven Salerno; Paul S García; Sachin Agarwal; David Roh; Soojin Park; Carl Bazil; Jan Claassen Journal: Clin Neurophysiol Date: 2021-01-20 Impact factor: 3.708
Authors: Yu Raymond Shao; Pegah Kahali; Timothy T Houle; Hao Deng; Christopher Colvin; Bradford C Dickerson; Emery N Brown; Patrick L Purdon Journal: Anesth Analg Date: 2020-11 Impact factor: 6.627