Caudal regional anesthesia, ropivacaine concentration, postoperative analgesia, and infants.

In this randomized, double-blind trial we evaluated the quality and duration of analgesia and motor effects after caudal block using 1 mL/kg of ropivacaine 0.1% (Group 1), 0.15% (Group 2), 0.175% (Group 3) compared to 0.2% (Group 4) in infants 1-12 mo old. Postoperatively, the number of infants who received pain medication differed among the groups (P < 0.0005). There were more infants in Groups 1 and 2 compared with Group 4 and there was no difference between Groups 3 and 4. In the postanesthesia care unit, infants in Groups 1 and 2 received more pain medication than did those in Group 4 (P = 0.0098). In the day surgery unit, there was a significant difference among the groups (P = 0.0326); infants in Groups 3 and 4 required no pain medication. The analgesia duration differed among the groups (P = 0.034). Infants in Groups 1 and 2 had a shorter duration, and there was no difference between Groups 3 and 4. Infants in Group 4 took longer to regain their motor power compared with those in Group 3 (P = 0.0347). We conclude that in infants, ropivacaine 0.175% provided postoperative analgesia and duration similar to that of ropivacaine 0.2%, whereas ropivacaine 0.1% and 0.15% did not, and it was associated with fewer motor effects.