Background and Aims: Central neuraxial blockade is the one of the most commonly performed technique in modern anesthesia. The basics for the combination of local anesthestics and opioids is that these two groups of drugs provide analgesia by their action at two different sites. Nalbuphine {mixed  antagonist and ĸ agonist} and Fentanyl {µ agonist} are two opioids. The aim of this study is to compare their onset of action and duration of sensory and motor blockade, post-operative analgesia and to see whether any side effects.

Materials and Methods: Fiftyfour patients belonging to ASA Ⅰ and ASA Ⅱ scheduled for infraumbilical surgery were divided into two groups of twenty-seven each. Group A received 0.5% hyperbaric Bupivacaine 3 ml (15 mg) plus Nalbuphine 1 mg in 0.5 ml normal saline. Group B received 0.5% hyperbaric 3 ml (15 mg) plus fentany l 25 mcg. Onset of actions of sensory and motor blockade, post-operative analgesia, hemodynamics and side effects were assessed.

Results: Onset, duration of sensory and motor blockade and duration of effective analgesia were comparable between both groups. mean onset time of sensory blockade of group A was 250.22±17.542 seconds and group B was 189.48±16.960 seconds. mean onset time of motor blockade in group A was 357.48±10.420 and group B was 343.56±8.317. Mean duration of sensory blockade (149.63±3.702 mins) and motor blockade (199.52±7.778 mins) of group A was highest compared to Group B in sensory blockade (133.48±5.072 mins) and motor blockade (184.81±7.000 mins) which was statistically significant (P < 0.001).

Conclusion: Nalbuphine had slower onset of sensory and motor blockade, while duration of motor blockade was prolonged in Nalbuphine group compared to fentanyl group.