Analgesia after upper abdominal surgery using extradural administration of a fixed dose of buprenorphine in combination with lignocaine given at two infusion rates: a comparative study.

BACKGROUND

Extradural administration of combinations of local anaesthetics and opioids are frequently employed for postoperative pain relief. There is a scarcity of data on the analgesic effects of variations of the dose of local anaesthetic drug admixed to a fixed dose of opioid.

METHODS

Twenty-four patients were investigated after elective upper abdominal surgery. During closure of the abdomen, 2% mepivacaine (8 ml) with buprenorphine 0.1 mg (0.5 ml) was given extradurally. After extubation, patients were randomly allocated to receive continuous extradural infusion of a fixed dose of buprenorphine (0.017 mg/h) in combination with 2% lignocaine at either 2.1 ml/h (low rate group, n = 14) or 6.3 ml/h (high rate group, n = 10). Postoperative pain at rest was assessed using visual analogue scale (VAS) scores and pain at movement by Prince Henry Pain Scale (PHPS) scores. Venous plasma lignocaine concentrations were measured.

RESULTS

VAS scores at rest were similar in the two groups at 3 h postoperatively, whereas at 6-24 h postoperatively, VAS scores were higher in the low rate group than in the high rate group. PHPS scores were similar in the two groups at 3 h and at 18 h postoperatively, whereas at 6, 9, 12 and 24 h postoperatively, PHPS scores were higher in the low rate group than in the high rate group. Plasma lignocaine concentrations were higher at 23 h postoperatively in the high rate group than at 16 h in both groups, and at 23 h in the low rate group. At 3 h postoperatively, both the systolic and diastolic arterial pressures were higher in the low rate group than control values obtained on admission. Side effects were observed in one patient in the low rate group who complained of dizziness, and in one patient in the high rate group who complained of nausea.

CONCLUSIONS

When added to a fixed dose of buprenorphine, continuous extradural infusion of 2% lignocaine at high rate provides better postoperative analgesia than when given at low rate without producing significant side effects.