Dexmedetomidine attenuates the positive chronotropic effects of intravenous atropine in patients with bradycardia during spinal anaesthesia: a retrospective study

INTRODUCTION: Dexmedetomidine is a sedative used during spinal anaesthesia. However, it frequently induces bradycardia. Although intravenous atropine is often used for treating bradycardia during regional anaesthesia, the response to atropine might be attenuated by concomitantly administering sedatives. METHODS: We examined the effects of atropine used for treating bradycardia during spinal anaesthesia among patients receiving dexmedetomidine (D group), propofol (P group), or neither (nonDnonP group) for sedation, retrospectively. RESULTS: A total of 108 patients were included. Heart rate was significantly slower at all time points in the D group (n = 69) than in the nonDnonP group (n = 14) (p < 0.025 for all). On the other hand, heart rate was significantly slower only 60 min after administration of atropine in the P group (n = 25) than in the nonDnonP group (p = 0.002). There were differences in the overall values of heart rate (including all the values from time 0 to 60 min) among the three groups (p = 0.026). CONCLUSIONS: The positive chronotropic effects of atropine might be attenuated with the use of dexmedetomidine or propofol during spinal anaesthesia. Although atropine may be administered when bradycardia occurs, a dose of atropine might result in an insufficient effect against the bradycardia. The sufficient number of subjects may change the results of the investigation, and large-scale randomised controlled trials will be necessary.