Effect of wound infiltration with bupivacaine on pulmonary function after elective lower abdominal operations

Background: Subcutaneous or intrafascial wound infiltration of local anaesthetic with systemic opioids has been shown to enhance patient comfort with improved analgesia and reduced opioid requirements.. Objective: To demonstrate improved pulmonary function when postoperative analgesia was provided by combined bupivacaine wound infiltration and systemic opioid. Methods: In a prospective, randomized, placebo-controlled study, 46 patients (23 per group) scheduled for elective gynaecological surgery under general anaesthesia had subcutaneous and intrafascial wound infiltration of 40 ml, 0.25% bupivacaine (study patients) or 40 ml 0.9% saline (control) just before the end of surgery. Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1) and peak expiratory flow rate (PEFR) were done before surgery and at 6, 12 and 24 hours postoperatively. Student's T and chi-square tests were used for tests of significance set at P < 0.05. Postoperative analgesia was provided with intramuscular morphine 0.15mg/kg 4hourly and 10mg/kg of intravenous paracetamol as rescue analgesia. Results: PEFR, FVC and FEV1 were reduced in both the control and study groups but the reduction was greater in the control group. Conclusion: Bupivacaine wound infiltration produced statistically significant elevations in pulmonary function tests results at all assessment periods.