Abstract
The postoperative analgesia afforded after colonic surgery by IV opioid, clonidine and lignocaine given intra- and postoperatively was evaluated. In a double-blind randomised trial, 80 male patients scheduled for colonic resection under general anaesthesia received fentany 15 μg.kg−1 at induction and another 4 μg.kg−1 before skin incision (group A) or fentanyl (same dose) plus clonidine 4 μg.kg−1 in 20 min + 2 μg.kg−1.h−1 (group B, C) or fentanyl plus clonidine (same dosage) plus lignocaine 2 mg.kg−1 before skin incision, repeated before peritoneal incision and retractor placement (group D). In the four groups, intraoperative boluses of fentanyl 2 μg.kg−1 were given in response to the painful stimulation of the procedure. Postoperative pain was managed with PCA delivering 2 mg morphine per request in group A, 1.5 mg morphine in group B, 1.5 mg morphine + 15 μg clonidine in group C and 1.2 mg morphine + 15 μg clonidine + 23 mg lignocaine in group D.
Postoperative analgesia was assessed by recording the analgesic demands (met and unmet) and the dose of morphine delivered at 6, 12, 18, 24, 36 hours. Side-effects, pain and sedation analogue scores were also recorded. A nalgesic demands and delivered morphine dose were reduced, at any time interval considered, in groups B, C, D, compared with A (P <0.001). No differences were noted between the groups B, C, D. Pain analogue scores were better in groups B, C, D compared with group A (P <0.001). Sedation and side-effects were not increased in groups B, C, D.
Intraoperative clonidine was the major determinant of the reduction in analgesic demands and morphine delivered. Lignocaine, at the dose used, failed to afford any additional benefit.