A Systematic Review of the Effective Dose of Intrathecal Ropivacaine for Cesarean Section

Ropivacaine is a frequently used agent in neuraxial anesthesia for cesarean section (C-section). The optimal dose has not been determined yet, and reported doses vary significantly. Higher doses are associated with higher success of anesthesia but also higher rates of adverse effects, such as hypotension. This study aimed to critically appraise current literature in order to determine the optimal dose of ropivacaine, as well as to highlight gaps in current knowledge. Systematic review of comparative studies, without an attempt at meta-analysis due to expected heterogeneity in examined arms. Medical Literature Analysis and Retrieval System Online (MEDLINE), Scopus, and Web of Science were accessed to look for pertinent studies written in English, regardless of time of publication. Included studies compared groups with at least two different doses of ropivacaine for neuraxial anesthesia for C-section in adults. Ten randomized control trials fulfilled eligibility criteria and included a total of 756 patients. Examined doses varied significantly, with 4 mg being the lowest and 25 mg being the highest. The success rate of neuraxial anesthesia ranged from 8.3% to 100%, with this extensive variance being attributed to significant heterogeneity in doses, the definition of success, and methods of measuring it. The effective dose for 50% of patients (ED50) ranged from 6.1 mg to 16.7 mg, while the effective dose for 95% of patients (ED95) ranged from 11.4 mg to 26.8 mg. Quality assessment of studies revealed no significant bias. Current literature on the optimal dose of ropivacaine consists of average and high-quality studies. Those ranked as best describe an ED50 of 8 to 10 mg and an ED95 of 12 to 15 mg. However, the large heterogeneity of tested doses and measures needs to be highlighted, as well as the lack of representation of patients at the upper normal of height.