Effect of different doses of intrathecal nalbuphine as adjuvant to ropivacaine in elective lower limb surgeries: A dose finding study

Background and Aim: Nalbuphine as an adjuvant intrathecally can produce significant analgesia with minimal side effects. However, no research has been done with isobaric ropivacaine. We, therefore, in this prospective, randomised double-blind study tried to find the optimal dose of intrathecal nalbuphine with isobaric 0.75% ropivacaine for elective lower limb surgeries. Materials and Methods: One hundred American Society of Anaesthesiologists I and II patients undergoing elective lower limb surgery were divided into four groups randomly: groups A, B, C and D, who received 0.5 mL normal saline or 0.4, 0.8 and 1.6 mg nalbuphine made up to 0.5 mL normal saline added to 22.5 mg (total volume 3.5 mL) isobaric 0.75% ropivacaine, respectively. The onset of sensory and motor block, two-segment regression time, duration of sensory and motor block, Visual Analogue Scale (VAS) and the incidence of adverse effects were compared between the groups. Results: The onset of both sensory and motor blockade was faster with addition of 0.4, 0.8 and 1.6 mg of nalbuphine when compared with ropivacaine alone; however, it was not statistically significant (P > 0.05). Two-segment regression time and duration of analgesia and motor blockade were highest with 1.6 mg of nalbuphine followed by 0.8, 0.4 and plain 0.75% ropivacaine (P < 0.05). The duration of sensory blockade in all four groups was slightly more than the duration of motor blockade. VAS readings were comparable in all nalbuphine groups when compared with ropivacaine group. Haemodynamic variability among the four groups was comparable. Incidence of adverse effects was highest in the 1.6-mg group when compared with others, although it was statistically insignificant (P > 0.05). Conclusion: Nalbuphine can be a good alternative to other opioids as an adjuvant intrathecally to prolong postoperative analgesia with a minimal side effect profile. Addition of nalbuphine to isobaric 0.75% ropivacaine gives the added advantage of significant analgesia with early motor recovery. We infer from our study that when compared with 1.6 mg of nalbuphine, both 0.4 and 0.8 mg nalbuphine are equally good as adjuvants to isobaric 0.75% ropivacaine in elective lower limb surgeries with prolonged analgesia, a reliable block with equal efficacy but with lesser side effects.