The dose-response of caudal ropivacaine in children

Background: Ropivacaine, a new local anesthetic, is less cardiotoxic in adults and is less likely to cause motor blockade than is bupivacaine. The authors evaluated the clinical effectiveness and hemodynamic effects of ropivacaine compared with bupivacaine and the pharmacokinetics of ropivacaine when given for caudal blocks in 56 children 4.1 +/- 1.2 yr old (mean +/- SD). Methods: Patients scheduled for inguinal hernia repair were randomly given a caudal injection (0.75 ml/kg) of ropivacaine, 0.25% (R0.25 group); ropivacaine, 0.5% (R0.5 group); or bupivacaine, 0.25% (B0.25 group). Postoperative measurements included the duration of analgesia, which was our primary outcome variable, and hemodynamic and respiratory monitoring for 4 h in the recovery room. Thereafter, analgesic requirements for the following 24 h were assessed by an independent observer on the ward using an observational pain-discomfort scale, which gives a cumulative score from 5 to 15 to estimate the quality of analgesia by assessment of behavioral objective parameters. Plasma levels of ropivacaine were measured before the procedure was started and 5, 10, 15, 20, 25, 30, and 45 min and 1, 2, 4, 6, 8, and 24 h after caudal block. Results: A significantly longer (P < 0.0001) duration of analgesia (median [range]) was observed in the R0.5 group (1,440 [335-1,440] min), whereas the R0.25 group (208 [175-340] min) and the B0.25 group (220 [100-390] min) were comparable. All groups showed a significant decrease in mean arterial blood pressure and heart rate from baseline values, but differences between groups were not observed. Conclusion: Ropivacaine is well tolerated and provides effective analgesia when given for caudal blockade in small children for inguinal hernia repair.