The dose-response of caudal ropivacaine in children

Background: Ropivacaine, a new local anesthetic, is less cardiotoxic in adu lts and is less likely to cause motor blockade than is bupivacaine. The aut hors evaluated the clinical effectiveness and hemodynamic effects of ropiva caine compared with bupivacaine and the pharmacokinetics of ropivacaine whe n 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); ropiva caine, 0.5% (R0.5 group); or bupivacaine, 0.25% (B0.25 group). Postoperativ e measurements included the duration of analgesia, which was our primary ou tcome variable, and hemodynamic and respiratory monitoring for 4 h in the r ecovery room. Thereafter, analgesic requirements for the following 24 h wer e assessed by an independent observer on the ward using an observational pa in-discomfort scale, which gives a cumulative score from 5 to 15 to estimat e the quality of analgesia by assessment of behavioral objective parameters . Plasma levels of ropivacaine were measured before the procedure was start ed 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 th e R0.25 group (208 [175-340] min) and the B0.25 group (220 [100-390] min) w ere comparable. All groups showed a significant decrease in mean arterial b lood 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 .