Opioid-sparing effect of bupivacaine wound infiltration after lower abdominal operations

Pain management has traditionally been provided by opioid analgesics. However, the reluctance of some health personnel to prescribe or administer opioids because of the fear of side effects has hindered their use. Local anaesthetic wound infiltration has been shown to improve postoperative pain management.

To determine the efficacy of combined subfascial and subcutaneous infiltration of bupivacaine in providing an opioid- sparing effect following abdominal surgery.

It was a prospective, randomized, double blind, placebo-controlled study.

The study was carried out at the University of Ilorin Teaching Hospital, Ilorin, Nigeria.

The study group received subcutaneous and subfascial infiltration with 40ml of 0.25% bupivacaine while the control group received 40ml of 0.9% saline administered by the surgeon after the closure of the peritoneum. Postoperative analgesia was provided with intramuscular morphine 0.1mg/kg 4hourly on demand and the time to first analgesic request was noted. Intravenous paracetamol was used as rescue analgesia. Postoperative pain was assessed using the verbal rating scale (VRS) at 6, 12 and 24 hours postoperatively at rest and during coughing.

The mean time to first analgesic request was significantly prolonged (p <0.05) in the study group (174 ± 117.6 min) than in the control group (102 ± 84 min). The patients in the control group received more morphine which was not statistically significant (p > 0.05). Request for rescue analgesia and the patients' impression of the analgesia were not significant (Fishers exact test two tailed p-value = 0.7164 and 0.4506 respectively).

Bupicacaine wound infiltration improved pain scores at rest within the first 6 hours and pain scores on coughing within the first 24 hours postoperatively. Although the technique increases the options available for postoperative pain relief after lower abdominal surgery, it cannot be used alone in this type of surgery.