Transdermal nitroglycerine enhances postoperative analgesia of intrathecal neostigmine following abdominal hysterectomies

This study was carried out to assess the effect of nitroglycerine (transdermal) on intrathecal neostigmine with bupivacaine on postoperative analgesia and note the incidence of adverse effects, if any. After taking informed consent, 120 patients of ASA Grade I and II were systematically randomised into four groups of 30 each. Patients were premedicated with midazolam 0.05 mg/kg intravenously and hydration with Ringer's lactate solution 10ml/kg preoperatively in the holding room. Group I patients received Intrathecal injection of 15 mg bupivacaine with 1ml of normal saline and transdermal placebo patch. Group II patients received Intrathecal injection of 15 mg bupivacaine with 5 mcg of neostigmine and transdermal placebo patch. Group III patients received Intrathecal injection of 15 mg bupivacaine with 1ml of normal saline with transdermal nitroglycerine patch (5 mg/24 hours). Group IV patients received Intrathecal injection of 15 mg bupivacaine with 5mcg of neostigmine and transdermal nitroglycerine patch (5 mg/24 hours), applied on a non anaesthetised area after 20 minutes. Groups were demographically similar and did not differ in intraoperative characteristics like sensory block, motor block, haemodynamic parameters and SpO(2). The mean duration of analgesia was 202.17 minutes, 407.20 minutes, 207.53 minutes and 581.63 minutes in control group (I), neostigmine group (II), nitroglycerine group (III) and nitroglycerine neostigmine group (IV) respectively (P<0.01). To conclude, our results show that transdermal nitroglycerine itself does not show any analgesic potential but it enhances the analgesic potential of intrathecal neostigmine.