A Comparative Study of Intrathecal Isobaric 0.5% Bupivacaine and Intrathecal Isobaric 0.75% Ropivacaine in Elective Lower Segment Cesarean Section

IntroductIonSubarachnoid block has been the gold standard for providing anesthesia in lower segment cesarean section (LSCS) with advantages such as with rapid onset of action, being easy to perform, being an effective anesthesia in mother, and with least fetal toxicity, being a few of them.[1] Bupivacaine, a long-acting amide local anesthetic (LA), is used most commonly for spinal anesthesia (SA), both as a hyperbaric and isobaric solution.[2] However, the major concern about the cardiotoxicity of bupivacaine led to the development of ropivacaine, a new long-acting amide LA. [3] Ropivacaine, a pure S-enantiomer, is less cardiotoxic, has shorter duration of action, and has lesser lipid solubility than bupivacaine.[4] Ropivacaine also exhibits differential blockade property (sensory > motor), leading to early return of motor activity and postoperative ambulation.[5] Various studies till date have compared the efficacy and side effect profile of equipotent doses of intrathecal hyperbaric bupivacaine and hyperbaric or isobaric ropivacaine both with and without adjuvants in different types of surgeries.[6] However, our novel study was undertaken with the primary aim to compare the anesthetic efficacy of intrathecal use of isobaric 0.75% ropivacaine (18.75 mg) and isobaric Objective: To compare the anesthetic efficacy of isobaric 0.75% ropivacaine with isobaric 0.5% bupivacaine in patients undergoing elective lower segment cesarean section (LSCS) under spinal anesthesia (SA) with respect to the nature of sensory block, motor block, and duration of analgesia.Materials and Methods: In this prospective, randomized, double-blinded study, sixty full-term parturients of American Society of Anesthesiologists Grade I-II, aged 20-35 years, scheduled for elective LSCS, were randomized into two groups namely B and R (n = 30).Preoperative medication regimen and anesthesia protocol followed, were uniform for all patients.Patients received 2.5 ml of either local anesthetic agent intrathecally.Hemodynamic parameters, onset and duration of sensory and motor blockade, level achieved, and side effects were compared between the two groups.Postoperative analgesia was assessed using the Visual Analog Scale scoring and also by noting the time of requirement of the first dose of rescue analgesic.Qualitative data were analyzed by Chi-square test and quantitative data were analyzed by independent sample t-test.Results: All the thirty patients in each arm completed the study without any dropouts.Baseline demographic variables, hemodynamic parameters, characteristics of sensory block (onset, time to reach peak sensory level, and duration), postoperative analgesia, and neonatal outcome were similar in both groups.However, intrathecal isobaric 0.75% ropivacaine demonstrated delayed onset (P = 0.005), and a significantly shorter duration (P = 0.001) of motor block.Conclusion: In view of the shorter duration of motor blockade, with similar duration of sensory blockade, hemodynamics, and postoperative analgesia, 0.75% isobaric ropivacaine (18.75 mg) is an efficient and safe alternative to bupivacaine for SA in elective LSCS.