Effects of pentolinium on blood sugar and serum potassium concentrations during anaesthesia and surgery

Blood surgar and serum potassium (K+) concentrations were measured before, during and 60 min after surgery in two groups of 10 non-diabetic patients during nitrous oxide/halothane/tubocurarine anaesthesia. In the control group the arterial pressure was maintained within the patients' normal ranges, while in the study group pentolinium was administered i.v. (average 22 mg per patient) to achieve and maintain a mean arterial pressure of 50 mm Hg (+/-10 SEM). In the normotensive group the blood sugar concentration increased markedly and significantly during surgery and in the early postoperative period while the serum K+ concentration was essentially unchanged. In the hypotensive group pentolinium produced a striking modification of the surgery-induced hyperglycaemic response (but not to hypoglycaemic values) as well as a small but significant decrease in serum K+ concentration. The observed increase in the blood sugar concentration may be part of the autonomic response to surgical stress. Two mechanisms can explain the reduction in serum K+ concentration: (1) decreased hepatic glycogenolysis and (2) attenuation of the suppressive effect of adrenaline on insulin release, both effects being secondary to the ganglion-blocking property of pentolinium. These results are in contrast to the widely held belief that ganglion-blocking drugs cause hypoglycaemia.