EFFECTS OF THE EXTRADURAL ADMINISTRATION OF MORPHINE, OR BUPIVACAINE, ON THE ENDOCRINE RESPONSE TO UPPER ABDOMINAL SURGERY

The endocrine response, and the relief of pain, following theextradural administration of morphine or a local anaestheticagent bupivacaine (0.5%) were studied for 24 h after abdominalsurgery and compared with a control group given conventionali.v. morphine after operation. Samples were taken before andat 2, 4, 6, 12 and 24 h after skin incision. Pain relief inboth extradural groups was significantly better when comparedwith the control group. In all three groups, the plasma concentrationof cortisol was increased immediately after surgery. Thereafter,significantly lower values were seen in the extradural groups.Plasma adrenaline concentration was lower immediately aftersurgery only in the group given the extradural local anaesthetic.Plasma noradrenaline concentration remained unchanged afterextradural local anaesthesia while an intermediate increaseoccurred after extradural morphine. Plasma noradrenaline concentrationwas significantly greater in the controls compared with bothextradural groups. Our results indicate that extradural analgesiawith a local anaesthetic drug can suppress the increases inthe plasma concentrations of the catecholamines and cortisolafter surgery. In contrast to extradural local anaesthetic extraduralmorphine cannot suppress the endocrine response immediatelyafter surgery. However, later in the postoperative period, extraduralmorphine can suppress the endocrine response, thus indicatingthat postoperative pain is a factor involved in the stress responsefollowing surgery.