Comparison of Two Different Doses of Nalbuphine With Isobaric Ropivacaine in Patients Undergoing Lower Segment Cesarean Section Under Subarachnoid Block: A Randomized Controlled Trial

Introduction: Obstetric analgesia and anesthesia is a challenge in itself. It requires an understanding of the physiological changes during pregnancy and labor and the effect of anesthetic agents on the fetus and newborn. Because neuraxial techniques provide superior analgesia and materno-fetal benefits, their use have increased significantly over the past three decades or so. A combination of local anesthetics like ropivacaine with opioids like nalbuphine has been shown to have additive beneficial effects in subarachnoid block (SAB) in lower segment cesarean section (LSCS). However, the optimal dose combination of ropivacaine and nalbuphine to maximize their benefits and minimize side effects remains to be established. Our study has compared the clinical efficacy and safety of 0.75% isobaric ropivacaine (15 mg) with two different doses of nalbuphine (0.4 mg and 0.6 mg) when given intrathecally for LSCS in terms of quality of sensory and motor blocks, hemodynamic parameters, duration of effective analgesia, Apgar score in newborn, and associated side effects. Method and materials: In this prospective, randomized, double-blind study, a total of 69 parturients between the age of 20-45 years, belonging to American Society of Anesthesiologists (ASA) grade I and II, undergoing cesarean section under SAB were evaluated. Patients were randomly allocated into three groups of 23 each by using the draw-of-lots technique. The patient and the observer were kept blinded as to which dose of drug (intrathecal) was being given to the patient. Patients in Group A received 0.75% isobaric ropivacaine 15 mg (2 ml) + 0.3 ml normal saline; patients in Group B received 0.75% isobaric ropivacaine 15 mg (2 ml) + 0.4 mg of nalbuphine (0.2 ml) + 0.1 ml normal saline; patients in Group C received 0.75% isobaric ropivacaine 15 mg (2 ml) + 0.6 mg of nalbuphine (0.3 ml). The total volume of drug solution in all three groups was 2.3 ml. Result: We found that the time to onset of sensory block was shortest in Group A (5.87±1.290 minutes) followed by Group C (6.00±1.087 minutes) and Group B (6.17±1.696 minutes); time to two-segment regression of sensory block was longest in Group C (101.74±8.996 minutes) followed by Group B (85.87±15.348 minutes) and Group A (65.00±7.071 minutes); duration of effective analgesia was longest in Group C (206.09±18.766 minutes) followed by Group B (183.91±15.880 minutes) and Group A (121.74±11.833 minutes); and time from SAB to complete regression of motor block was longest in Group C (216.52±15.553 minutes) followed by Group B (203.48±20.138 minutes) and Group A (174.78±14.731 minutes). Side effects were comparable among all three groups. Conclusion: The optimal dose combination in SAB for cesarean section was 15 mg of 0.75% isobaric ropivacaine + 0.6 mg nalbuphine, with minimal side effects.