DYNAMICS OF MLAEP CHANGES IN MIDAZOLAM-INDUCED SEDATION

This study aimed at assessing the effects of midazolam (MDZ) sedation on auditory brainstem (BAEP) and middle latency (MLAEP) evoked potenti als in intensive care conditions. Ten ventilated comatose patients wer e receiving an intravenous MDZ bolus dose (0.2 mg/kg) followed by a 2 h continuous infusion (0.1 mg/kg/h). MLAEPs and BAEPs elicited by clic ks (90 dB HL + masking) were simultaneously and continuously monitored during the first 6 h and for 30 min the next morning. We found no eff ect of MDZ sedation on BAEPs. Only MLAEP components were modified. How ever, none of the patients presented any total abolition of the MLAEPs . Bolus injection led to very early alteration of cortical responses, beginning after 5 min and lasting almost 1 h (maximum Pa latency incre ase, 3.1 ms; maximum Pa-Nb amplitude decrease, 46%). During continuous infusion, MLAEPs remained slightly, although significantly, altered ( Pa latency, +1.3 ms; Pa-Nb amplitude, 27%). The Nb wave seemed to be m odified earlier and to return to normality later than the Pa wave. The se findings incite a careful interpretation of MLAEP tracings acquired during the first hour following MDZ bolus injection. If possible, MDZ should be administered as continuous infusion for reliable interpreta tion of evoked potential changes in intensive care unit, or during sur gery. (C) 1997 Elsevier Science Ireland Ltd.