Effect of pre- vs postoperative inguinal field block on postoperative pain after herniorrhaphy

The analgesic effects of an identical inguinal field block, performed before or immediately after inguinal herniorrhaphy, were evaluated in 32 healthy patients in a double-blind, randomized study. During surgery, all patients received a light general anaesthesia with thiopentone, alfentanil and nitrous oxide in oxygen. After induction of general anaesthesia, patients were allocated randomly to receive an inguinal field block with lignocaine, either 15 min before operation or immediately after operation, after closure of the surgical wound, but before the patients were awake. Pain score on a visual analogue scale and on a verbal scale at rest, during mobilization from supine into sitting position and during cough was assessed 1, 2, 4, 6, 8 and 24 h, and 7 days after operation. No significant differences between the groups were observed in VAS scores or verbal pain scores during rest or ambulation at any time. There was no significant difference in time to first request for morphine or total morphine consumption. These results do not show pre-emptive analgesia with a conventional inguinal field block to be of clinical importance compared with a similar block administered after operation.