Introduction: Opioids when added to local an aesthetic for sub arachnoid block are known to prolong postoperative an algesiaas the two drugs act at different sites.

Aim: To compare µ opioid agonist fentanyl and partial agonist nalbuphine for post-operative analgesia, hemodynamic parameters and adverse effects as and juvant to hyperbaric bupivacaine

Material and Methods: Sixty patients of either sex, scheduled for elective lower limb surgeries under sub arachnoid block belonging to ASA class Ι and ΙΙ were included in this study. Patients received 0.5% hyperbaric bupivacaine 15 mg along with either 25mcg fentanyl or 0.8mg nalbuphine hydrochloride. Onset and duration of sensory and motor block, hemodynamic parameters, adverse effects, effective duration of analgesia and postoperative VAS scores and sedation scores were noted.

Results: Duration of postoperative analgesia was significantly longer with nalbuphine (318±13.88 min)as compared to fentanyl (296.26±13.31min). Side effects like nausea vomiting, hypotension and bradycardia and shivering was more with fentanyl while sedation was minimal with both the drugs.

Conclusion: Nalbuphine hydrochloride is a better alternative as an adjuvant for postoperative analgesia and less side effects than fentanyl for lower limb surgeries.