COMPARATIVE-EVALUATION OF 4 DIFFERENT INFUSION RATES OF ROPIVACAINE (2 MG ML) FOR EPIDURAL LABOR ANALGESIA/

Background and Objectives. Previous studies have reported comparable e fficacy for ropivacaine and bupivacaine when used for labor analgesia at concentrations of 2.5 mg/mL. In this multicenter study, we assessed ropivacaine at the commercially available concentration of 2 mg/mL (0 .2%) for labor pain management. Methods. After Institutional Review Bo ard approval and informed consent, 128 women at term were randomly ass igned to receive ropivacaine at one of the four infusion rates via a l umbar epidural catheter. Analgesia was initiated with a 5-mL test dose , followed by injections of 5-15 mt of 2 mg/mL ropivacaine. The contin uous infusion was then started at 4, 6, 8, or 10 mL/hour. Rescue analg esia was provided with 5-mL ''top-up'' injections as necessary to prov ide maternal comfort. Pain relief was assessed by using a visual analo g pain scale (VAPS) and motor block was assessed by using a modified B romage scale. Results. All infusion regimens effectively decreased VAP S, and most patients in all groups had minimal or no motor block at th e end of the first stage of labor. Mean total number of the top-up inj ections required per patient were 3, 2, 1.5, and 1.4 respectively, in the 4, 6, 8, and 10-mL/hour groups (P < .05, 4 mL/hour vs. all other g roups). Despite receiving more total bolus dosages, the 4 mL/hour grou p had less motor block in the lower extremities (P < .05). Apgar score s and neurological adaptive capacity scores were similar for all group s. Conclusions. The 2 mg/mL of ropivacaine produces satisfactory labor analgesia at epidural infusion rates of 4, 6, 8, and 10 mL/hour, prov ided supplemental bolus dosages are available. Clinically, a rate of 6 mL/hour may be the lowest effective rate that provides the best combi nation of pain relief, motor block, and rebolusing, although rates of 8 and 10 mL/hour produced similar results.