Abstract 200: Glycopyrrolate Does Not Ameliorate Bradycardia During Prolonged Cooling in Awake Subjects

Introduction: Hypothermia may help improve outcomes in patients with large vessel occlusion cerebrovascular accidents or other reversible ischemia. Dexmedetomidine infusion reduces shivering in awake subjects undergoing hypothermia but has dose-limiting bradycardia. If vagally mediated, anticholinergic drugs might reduce bradycardia. Hypothesis: Glycopyrrolate prevents bradycardia during dexmedetomidine-assisted prolonged hypothermia. Methods: Eight healthy subjects were randomly assigned to 0.4mg glycopyrrolate bolus, glycopyrrolate rescue (0.01mg every 3 minutes as needed for heart rate <50), or no glycopyrrolate during three separate sessions of 3 hours cooling. Following 1mg/kg dexmedetomidine bolus, subjects received 20cc/kg of (4 0 C) cold saline and surface cooling (EM COOLS, Weinerdorf Austria). Dexmedetomidine infusion was titrated to suppress shivering but allow arousal to verbal stimuli. After 3 hours of cooling, we allowed subjects to rewarm. We compared heart rate, core temperature, and mean arterial blood pressure between groups using Kruskal-Wallis test and ANOVA. Results: Mean age was 27 (SD 6) years and most (N=6, 75%) were male. Mean pre-treatment resting heart rate was 73 [SD 13] bpm. Neither heart rate nor core temperature differed between the groups during the stable hypothermia period (p>0.05). (Figure) Mean arterial blood pressure was higher in the glycopyrrolate bolus group than the other two groups during the study period (p<0.048). Conclusions: Glycopyrrolate did not prevent the bradycardic response to hypothermia and dexmedetomidine. Mean arterial blood pressure was higher in subjects receiving a bolus of glycopyrrolate before induction of hypothermia.