The effects of ketamine and rocuronium on the A-line® auditory evoked potential index, Bispectral Index, and spectral entropy monitor during steady state propofol and remifentanil anesthesia

Background: The authors studied the effects of ketamine and rocuronium on the Bispectral Index, A-Line (R) auditory evoked potential index, state entropy, and response entropy during a calculated steady state anesthesia with propofol and remifentanil. Methods: After ethics committee approval, 42 patients were allocated to four groups. Baseline measurements were performed after implementing a calculated steady state anesthesia with propofol and remifentanil. The control group received no additional medication. The ketamine group received a bolus and continuous infusion of ketamine. The rocuronium group received a bolus of rocuronium. The rocuronium-ketamine group received both. All data were stored during 15 min after baseline. After inspection of the raw data, the authors conducted an explorative statistical analysis. Results: No significant changes were found in the control group for any of the monitors. Mean values decreased in die rocuronium group for the A-Line (R) auditory evoked potential index, Bispectral Index, and response entropy, but not for state entropy. in the ketamine group, the A-Line (R) auditory evoked potential index and Bispectral Index did not change significantly, but state and response entropy increased. in the rocuronium-ketamine group, the A-Line (R) auditory evoked potential index and Bispectral index did not decrease as found in the rocuronium, group. Response and state entropy increased significantly. Conclusions: The response of all monitors after ketamine administration is not affected by simultaneous administration of rocuronium. Interpretation of all studied indices must be done cautiously while taking into account the clinical setting during measurement.