Comparison of nalbuphine versus fentanyl as an adjuvant to 0.75% isobaric ropivacaine in subarachnoid block for orthopedic surgery of lower limbs: A randomized, double-blind study

Background: Ropivacaine is an effective and safe alternative local anesthetic for subarachnoid block with a lesser duration of motor blockade and less neuro-cardiotoxicity. While fentanyl is commonly used as an adjuvant, nalbuphine recently got popular by its μ-attenuation and k-accentuation effects. We compared the efficacy of intrathecal fentanyl versus nalbuphine as an adjuvant to ropivacaine in subarachnoid block. Materials and Methods: In this prospective, randomized, double-blind study, seventy adult patients who were posted for elective lower limb orthopedic surgeries were randomly allocated to two groups. Group F received 22.5 mg of 0.75% isobaric ropivacaine with 25 μg fentanyl, and Group N received 22.5 mg of 0.75% isobaric ropivacaine with 1 mg nalbuphine intrathecally. Hemodynamics, onset, block duration, peak sensory level, two-segment regression time, and adverse effects such as nausea, vomiting, pruritus, sedation, hypotension, and bradycardia were studied. P < 0.05 was considered statistically significant. Results: Both groups achieved the target sensory level of T10. Time for onset of sensory and motor blockade, time to achieve peak sensory level, and motor block duration were statistically comparable in both groups. The duration of the sensory block was 254.45 ± 20.69 min in Group F and 297.4 ± 19.0 min in Group N (P < 0.001). The duration of analgesia was 275.6 ± 18.76 min in Group F and 318.2 ± 14.14 min in Group N (P < 0.001). Conclusions: Nalbuphine prolongs the duration of the sensory block along with the duration of postoperative analgesia in comparison to fentanyl as an intrathecal adjuvant to 0.75% isobaric ropivacaine for subarachnoid block