Effects of low dose ketamine on tourniquet-induced haemodynamic responses during general anaesthesia.

This study investigated the effect of a pre-operative low dose of intravenous ketamine on tourniquet-induced haemodynamic changes. Ten minutes after induction of general anaesthesia, 0.1 mg/kg ketamine in 10 ml of saline (ketamine group, n = 14) or 10 ml of normal saline (control group, n = 14) were administered intravenously. Systolic and diastolic blood pressures, and heart rate relative to tourniquet inflation and deflation were recorded and compared within and between groups. Systolic and diastolic blood pressures in the control group significantly increased relative to baseline during the observation period following tourniquet inflation, but generally did not significantly increase in the ketamine group. The control group had a greater percentage of patients with a 30% rise in blood pressure at 60 min after tourniquet inflation compared with the ketamine group (28.6% vs 7.1%), but this was not statistically significant. We conclude that a pre-operative low dose (0.1 mg/kg) of intravenous ketamine can prevent a systemic arterial pressure increase for at least 60 min after tourniquet inflation under general anaesthesia.