Cardiac sympathetic tone in anaesthetized diabetics.

To assess cardiac sympathetic nervous function in diabetics, the heart rates attained following a pharmacological dose of intravenous atropine, 23 micrograms.kg-1, were studied under N2O, isoflurane anaesthesia in diabetics (n = 21) and nondiabetics (n = 30). Atropine-induced heart rate in diabetics was significantly lower than that in nondiabetics (95 +/- 14 (SD) bpm vs 109 +/- 12 bpm, P less than 0.001) and were closely related to preoperative orthostatic diastolic blood pressure change (r = 0.60, P less than 0.01). There was some correlation between the atropine-induced heart rate and preoperative RR-variation in diabetics (r = 0.50, P less than 0.05). The findings suggest that cardiac sympathetic function may also be impaired in diabetics with orthostatic hypotension.