Analgesic effect of intrathecal neostigmine combined with bupivacaine and fentanyl.

BACKGROUND: The spinal route of analgesia has consolidated its place as a major modality in the management of both acute and chronic pain. The search for ideal additives to local anaesthetic agents to prolong the analgesic effects poses a challenge to the anaesthetists. Neostigmine, an anticholinesterase, presents a novel approach to providing analgesia. Neostigmine, when given intrathecally, inhibits breakdown of an endogenous spinal neurotransmitter, acetylcholine, thereby inducing analgesia. We aimed to determine the analgesic and adverse effects of intrathecal neostigmine combined with hyperbaric bupivacaine and fentanyl.

METHOD: Sixty male adults, ASA I-II requiring lower abdominal surgical procedures under spinal anaesthesia were randomly allocated to 2 groups: Neostigmine group, received intrathecal (IT) 0.5% hyperbaric bupivacaine 15 mg, fentanyl 25 microg and preservative-free neostigmine 25 microg while saline group, received same dose of bupivacaine and fentanyl plus 0.5 ml saline. The duration of analgesia, time to use first rescue analgesics and the incidence of adverse effects were recorded.

RESULTS: The mean duration of effective analgesia was 485.6 +/- 37.6 minutes in neostigmine group compared with saline group, 316.0 +/- 49.15 minutes, p < 0.001. Total analgesic consumption 12 hours post-intrathecal injection was also less in the neostigmine group. The incidence of adverse effects such as hypotension, bradycardia, nausea and vomiting were not statistically significant in both groups, p > 0.05.

CONCLUSION: This study showed that spinal neostigmine 25 microg added to hyperbaric bupivacaine and fentanyl provided a significantly longer surgical analgesia and insignificant adverse effects in male adults who had lower abdominal surgery under spinal anaesthesia.