To evaluate dose range on analgesic effect on ropivacaine in pediatric caudal anesthesia.

Eighty American Society of Anesthesiologist(ASA)physical status I children, aged 1 ~3 years, were admitted in West China Hospital, Sichuan University in 2007. They were randomly divided into four groups according to the varied ropivacaine concentration. After the sevoflurane inhalation induction, caudal injection was performed by a fixed catheter. As the basic anesthesia, 1 % lidocaine(1 mL/kg)was infused. One hour later, ropivacaine was given at different concentrations(1 mL/kg)to the group A(0. 075%), the group B(0. 100%), the group C(0. 125%). The group D children were the control group with saline solution(1 mL/kg). Informed consent was obtained from all participants. The major outcomes, like the analgesia duration and the numbers needed to treat were recorded after operation. Additional analgesia in the following 24 h was assessed by an independent expert of the Children and Infants Postoperative Pain Scale(CHIPPS)on the ward, and would be carried out once the Children and Infants Postoperative Pain Scale scores higher than or equal to four. Improved Bromage score was used to evaluate the lower limb motor blockade. The postoperative analgesia duration among different groups were calculated by Kanplan-Meimer survival analysis with the statistical inference at 0. 05.

Four groups had no significant difference with respect to the patient age, height, weight and surgical procedures. The postoperative analgesia duration of A, B, C and D groups were 5. 13 h(95%CI3. 90 h~6. 36 h), 7. 20 h(95 %CI 6. 46 h~7. 94 h), 7. 65 h(95%CI7. 25 h~8. 05 h)and 3. 78 h(95 %CI 2.45 h~5. 10 h), respectively. There was a significant difference among four groups(P<0. 01)and no difference between the group B and the group C(P>0. 05). Cases for additional analgesia were 11, 4, 3 and 14 in four groups.

Caudal ropivacaine 0. 100% can provide satisfactory postoperative analgesia for children undergoing elective sub-umbilical surgery at 1~3 years old.