Postoperative analgesic and adverse effects of two low doses of intrathecal neostigmine and its influence on spinal bupivacaine anaesthesia after knee arthroscopy

Background

Neostigmine is a spinal analgesic that could be a useful adjunct. This study was conducted to evaluate the postoperative analgesic efficacy and the safety of two low doses of intrathecal (IT) neostigmine in patients undergoing knee arthroscopy under spinal bupivacaine anaesthesia.

Methods

By using a double-blinded study design, 80 patients undergoing knee arthroscopy during spinal anaesthesia were divided into four groups: bupivacaine group (Group B) received 15 mg hyperbaric bupivacaine; bupivacaine + fentanyl group (Group BF) received 15 mg hyperbaric bupivacaine mixed with 25 μg fentanyl; bupivacaine + neostigmine group 1 (Group BN1) received 15 mg hyperbaric bupivacaine mixed with 25 μg neostigmine; bupivacaine + neostigmine group 2 (Group BN2) received 15 mg hyperbaric bupivacaine mixed with 35 μg neostigmine. The postoperative visual analog scale (VAS) and the incidence of adverse effects were recorded for 24 h after administration of study drugs.

Results

VAS scores were significantly lower in group BN2 compared with group B, group BF and group BN1 at 2, 4, 6, 12, and 24 h after operation (P < 0.05). The time to the first patients’ demand for morphine administration after surgery was significantly prolonged in group BN2 compared with group B or group BN1 (P < 0.05). There was no significant difference between four groups in incidence of nausea and vomiting.

Conclusion

Our study showed that IT neostigmine (35 μg) enhanced bupivacaine spinal anaesthesia (15 mg) and produced prolonged postoperative analgesia for about 24 h without producing significant more adverse effects such as nausea and vomiting.