We have studied the effect of continuous extradural analgesia with bupivacaine and morphine, initiated before or after colonic surgery, in a double-blind, randomized study. Thirty-two patients were allocated randomly to receive an identical extradural block initiated 40 min before surgical incision (n = 16) or at closure of the surgical wound (n = 16). The extradural regimen consisted of a bolus of 7 ml of plain bupivacaine 7.5 mg ml-1 plus morphine 2 mg and continuous extradural infusion of a mixture of bupivacaine 7.5 mg ml-1 plus morphine 0.05 mg ml-1, 4 ml h-1 for 2 h, followed by a continuous extradural infusion of a mixture of bupivacaine 2.5 mg ml-1 plus morphine 0.05 mg ml-1, 4 ml h-1, continued for 72 h after operation. In addition, all patients received similar general anaesthesia. There was no significant difference in request for additional morphine and no significant differences between the groups in pain scores (visual analogue scale or verbal) during rest or ambulation at any time of measurement. These results do not suggest that timing of analgesia with a conventional extradural regimen is of major clinical importance in patients undergoing colonic surgery.

The pharmacokinetics of ropivacaine were independent of dose, but total clearance decreased with time over 24 h. The consistent increase in total plasma concentration during the postoperative epidural infusion contrasted to much less variation in the unbound plasma concentrations of ropivacaine.

Pain threshold, nociceptive flexion reflex (NFR) threshold and responses to suprathreshold stimulation were investigated in 15 female patients (mean age 32 yr (range 22-48 yr)) before and 68 (range 48-96) h after gynaecological laparotomy. Control measurements were performed in 17 healthy human volunteers (five males, age 30 yr (range 24-41 yr)). In the surgical patients, pain threshold decreased and pain to suprathreshold stimulation increased significantly (P = 0.006 and P = 0.04, respectively) from before to after surgery. A corresponding trend was demonstrated in neurophysiological measurements, although the decrease in NFR threshold and increase in NFR amplitude to suprathreshold stimulation were not significant (P = 0.08 and P = 0.24, respectively). The correlations between the relative change in pain and reflex thresholds, and time from surgery, were statistically significant (pain threshold: rs = 0.53, P = 0.04; NFR thresholds: rs = 0.54, P = 0.04). In the healthy volunteers, no significant differences in thresholds and responses to suprathreshold stimulation were observed between two recordings with an interval of at least 48 h. The allodynia and hyperalgesia observed in postsurgical patients may be related to postoperative sensitization of central neurones.

In a double-blind, randomized study, 32 patients scheduled for elective inguinal herniotomy under general anaesthesia received subcutaneous infiltration with 40 ml ropivacaine 2.5 mg/ml or bupivacaine. Postoperative pain intensity was assessed repeatedly for 24 hours at rest, during cough and movement on a visual analogue scale (VAS) and by means of pressure algometry. No differences between pain intensities or wound tenderness were found between the groups. The demand for analgesics was similar in the two groups. We conclude that incisional ropivacaine is as effective as bupivacaine in the management of post-herniotomy pain.