Intrathecal neostigmine with hyperbaric bupivacaine on the effects of spinal anaesthesia and postoperative analgesia-randomised prospective double blind study

Postoperative analgesia after intrathecal bupivacaine is limited to a few hours. The aim of this study was to assess the effects of intrathecal Neostigmine added to hyperbaric bupivacaine on the onset and duration of spinal anaesthesia and in prolonging postoperative analgesia.

A prospective, randomized double blind study was conducted in 90 patients of ASA grades I and II, in three groups of 30 each, scheduled for lower limb surgeries under subarachnoid block. Patients in Group 1 received 0.5% hyperbaric Bupivacaine 2.5ml (12.5mg) + 0.1ml of sterile normal saline, Group 2 received 0.5% hyperbaric Bupivacaine 2.5ml (12.5mg) + 0.05ml Neostigmine (25μg) + 0.05 ml sterile normal saline and Group 3 received 0.5% hyperbaric Bupivacaine 2.5ml + 0.1ml Neostigmine (50μg). The onset and duration of sensory and motor block, time of two segment regression of sensory block, postoperative analgesia and side effects were studied.

The mean onset time of sensory and motor block were comparable in the three groups. The sensory and motor block were prolonged by the addition of Neostigmine, of which adding 50g Neostigmine was found to be statistically significant (p value <0.001). The visual analog scale (VAS) scores were significantly lower compared to control group upto 4 hours postoperatively in the 50g Neostigmine group.

50g Neostigmine is needed to produce significant prolongation of analgesia without significantly increasing the adverse effects, and it reduces the VAS score and analgesic consumption postoperatively.