Stress response and platelet function in minor surgery during epidural bupivacaine and general anaesthesia: effect of epidural morphine addition

Abstract

In a randomized study, thirty patients submitted to transarthroscopic meniscectomy were allocated to general or epidural anaesthesia with or without epidural morphine. Threshold concentration of collagen for platelet aggregation did not differ between the groups, but showed a similar pattern of increase, which was significant in the general anaesthesia group. Collagen-induced thromboxane-B2 synthesis was significantly lower in the epidural anaesthesia groups compared with the general anaesthesia group, and the addition of morphine caused a significant fall in thromboxane-B2 synthesis. The mean serum cortisol concentration increased in the general anaesthesia group, and decreased in the epidural groups. The difference between the groups was significant. Epidural morphine administration significantly decreased serum cortisol. During operation a thigh tourniquet was used. The removal of the tourniquet did not influence any of the measured variables. It can be concluded that the adrenocortical system is activated during general and inhibited during epidural anaesthesia. The addition of morphine during epidural anaesthesia further decreases the activity of the adrenocortical system, and the combined regime has an inhibiting effect on platelet function.