Analgesic effects of intrathecal bupivacaine with neostigmine or morphine among elective surgical patients in selected comprehensive specialised hospitals, Southern Ethiopia: a prospective cohort study.

Objectives: To compare the analgesic effects of intrathecal neostigmine with bupivacaine, morphine with bupivacaine and bupivacaine alone among patients undergoing surgical procedures below the umbilicus.

Design and setting: A multicentre prospective cohort study was conducted from 29 May to 29 August 2023 at Wolaita Sodo University Comprehensive Specialized Hospital, Nigest Mohammed Eleni Memorial Comprehensive Specialized Hospital and Werabe Comprehensive Specialized Hospital. A systematic random sampling technique was used to select the participants from the sample of 180.

Participants: The study included American Society of Anesthesiologists classes I and II patients aged 18-85 years scheduled for elective surgeries under spinal anaesthesia with bupivacaine with neostigmine (50 µg), bupivacaine with morphine (100 µg) and bupivacaine alone at a dose of 17.5 mg.

The primary outcome measures: The duration of pain relief, the severity of pain and the time of first analgesic requirement.

The secondary outcome measures: Postoperative complications such as respiratory depression, pruritus, nausea and vomiting RESULTS: Administration of intrathecal bupivacaine with neostigmine group (NG) and morphine group (MG), respectively, produces a long duration of postoperative analgesia with a first analgesia request mean time of 9.4±3.18 and 9.65±4.9, while using bupivacaine group (BG) alone produces a shorter duration of postoperative analgesia with a mean first analgesia request time of 3.58±0.98 hours. The mean visual analog scale scores in 28 hours were 0.99, 0.79 and 2.05 for the NG, MG and BG, respectively. The overall postoperative pain severity was highest in the BG. The mean total analgesic consumption was 77.5, 73.8 and 189.2 mg for diclofenac, whereas 54.2, 63.9 and 151.7 mg for tramadol in the NG, MG and BG, respectively. Incidence of nausea (31.3%) and vomiting (30%) was highest in the NG, while pruritus (15%) and respiratory depression (15%) were more in the MG.

Conclusion: Compared with BG, MG and NG had longer-lasting postoperative analgesic effects, less severe pain and required fewer analgesics overall. Patients in the NG had more incidences of nausea and vomiting. The incidences of pruritus and respiratory depression were highest in the MG. Effective analgesia appeared to work better in the MG and NG. We recommend morphine and neostigmine as adjuvants to local anaesthetics for effective postoperative analgesia. We also recommend researchers compare different doses of neostigmine and morphine as adjuvants to bupivacaine in further studies.