The effect of ketamine on the peripheral circulation: a possible sympathetic ganglion blocking effect

The effects of induction of anaesthesia, endotracheal intubation and surgical stimuli on the systemic and peripheral circulations were studied in three groups of patients. In group KA (n = 8) anaesthesia was induced with ketamine (2 mg kg-1) and alcuronium, supplemented by N2O-O2 alone; in group KAH (n = 9) 0.5% halothane was added to the N2O-O2; and in the control group TAH (n = 8) anaesthesia was induced with a sleep dose of thiopentone and alcuronium, supplemented by N2O-O2 and halothane. The circulation in the finger was monitored by photo-electric plethysmography. Induction produced a significant pressor response in both ketamine groups, but not in the TAH group, while the finger plethysmogram demonstrated peripheral vasodilatation in all three groups. Intubation, on the other hand, elicited a significant pressor response in the TAH and in the KAH group but not in the KA group. The finger plethysmogram, however, always showed peripheral vasoconstriction during intubation in the thiopentone group (TAH) but never in either of the ketamine groups. The results suggest that ketamine exerts a peripheral ganglion blocking effect.