Mismatch Negativity and General Anesthesia

Abstract

In order to further explore the nature of anesthesia-induced unconsciousness and its relationship to nociception, investigators attempted to determine whether mismatch negativity could be detected during general anesthesia and surgery. An auditory odd-ball paradigm designed to elicit mismatch negativity was presented to ten patients during general anesthesia and surgery. Five of the ten also underwent testing in the awake state prior to surgery. Multiple EEG recordings were obtained in each patient and each condition using the BioSemi ActiveTwo 64 EEG electrode system. The anesthetic regime required only that 0.7 MAC of an inhaled agent was administered. Several methods of analysis were utilized to determine whether an MMN response could be identified: visual inspection of ERP waveforms, targeted t-tests, cluster permutation tests, and multivariate pattern analysis. Whereas deviant-related negativity was readily detected in the awake state, deviant-related negativity was not detected during surgery and general anesthesia. Results demonstrate that essential components of the MMN response are abolished during typically conducted general anesthesia even with significant surgical stimulation. These results are consistent with previous research on ERPs and anesthesia. Results cast doubt on the possibility of sensory memory related to intraoperative events.