Comparison of analgesic efficacy and safety of bupivacaine plus ketamine versus bupivacaine alone in rectus sheath block for midline laparotomy

Background & Objective: Addition of ketamine affects pain modulation through multiple mechanisms and may enhance the analgesic effect of local anesthetics in rectus sheath block (RSB). However, limited studies have evaluated the analgesic efficacy and safety of ketamine added to RSB for midline laparotomy. We aimed to evaluate the analgesic efficacy and safety of ketamine as an adjuvant to 0.25% bupivacaine in ultrasound-guided RSB following major abdominal or gynecological surgery with midline incision. Methodology: Fifty-four patients of ASA class I−II, aged 18−65 y, who underwent midline laparotomy under general anesthesia were studied. The patients were randomly allocated to two groups: ultrasound-guided RSB was performed in the control group (n = 28) with 40 ml of 0.25% bupivacaine, while in the ketamine group (n = 28) it was performed with 40 ml of 0.25% bupivacaine plus ketamine 1 mg/kg. Postoperatively, both groups received IV morphine patient-controlled analgesia. The Numeric Rating Scale (NRS) pain scores at rest and on movement were assessed at 0, 1, 12 and 24 h postoperatively. The total 24-h postoperative morphine consumption and psychomimetic side effects were recorded. Results: The mean NRS pain score on movement was significantly lower in the ketamine group at most time points compared to the control group (P < 0.05). The ketamine group had a significantly reduced total 24 h postoperative morphine consumption (14.3 ± 6.55 mg) compared to the control group (21.86 ± 15.46 mg) (P < 0.05). No psychomimetic adverse effects were reported in both groups. Conclusion: The addition of ketamine to bupivacaine in RSB resulted in effective postoperative analgesia by reducing postoperative pain scores on movement in patients who underwent midline laparotomy. Such combination also reduced postoperative morphine requirement without serious side effects. Abbreviations: ERAS - Enhanced Recovery After Surgery; LA - Local anesthetics; NRS - Numeric Rating Scale; PAC - Patient-controlled analgesia; RSB - Rectus sheath block; Key words: adjuvant; Bupivacaine; Ketamine; Laparotomy; Rectus sheath block Citation: Hassan SK, Thang PY, Wan Shukeri WFWM, Ismet S. Comparison of analgesic efficacy and safety of bupivacaine plus ketamine versus bupivacaine alone in rectus sheath block for midline laparotomy. Anaesth. pain intensive care 2023;27(2):220−226. DOI: 10.35975/apic.v27i2.2188 Received: December 21, 2022; Reviewed: January 17, 2023; Accepted: January 19, 2023