Of the 66 patients studied in the analysis, one more patient in the control group was also excluded because of failure to localize the sciatic nerve with stimulator guidance (Figure ). The groups were comparable with respect to demographic data (age in years, weight, and sex), the type of operation, and the total anesthesia time (Table ). A remarkable similarity of attempts to the ease of sciatic nerve localization was observed (p = 0.503).
Demographic and surgical data of the study population
Intraoperatively in clonidine, and clonidine plus ropivacaine groups the hemodynamic parameters SAP, DAP, HR were maintained to the lower normal values so that no patient needed nalbuphine, under 0.6 MAC sevoflurane anesthesia. On the contrary, in the control group, increased sevoflurane concentration (MAC up to1.3), and nalbuphine infusion (0.09 mg/kg/h, mean value: 5.097 ± 3.33), were required in the patients, to maintain the parameters to the lower normal values until the end of the operation.
Postoperatively, the Kaplan- Meier analysis (Figure ), shows the time from the end of anesthesia to the first analgesic request which differed significantly between the three groups (overall p < 0.0005). Particularly, the patients in the clonidine plus ropivacaine group had a significantly longer time to first analgesic request compared to clonidine group (Figure ), [mean time: 21.5 hours, SEM: 1.26, SD:5.90, 95% CI:19.0-23.9 versus 11.6 hours, SEM:1.74 SD: 8.33, 95% CI: 8.2-15.1, median time: 24 hours, range:0-24, 95% CI: 21.6-26.4 versus 6 hours, range:6-24, 95% CI: 5.6-6.4], (p = 0.001). On the contrary to the control group that all patients required rescue nalbuphine in the recovery room (time:0), the patients in the clonidine group had a longer mean time to first rescue nalbuphine (p < 0.0005) (Figure ).
Kaplan-Meier analysis. Estimation of survival analysis of the time from the end of anesthesia to the first analgesic request in the Control, Clonidine and Clonidine plus 0.2% Ropivacaine groups.
The mean pain CAS score also differed significantly between the three groups (overall p < 0.0005), (Figure ). In the recovery room (time 0) the mean pain CAS score was similar in normal values concerning the clonidine and clonidine plus ropivacaine groups and significantly lower than in the control group (p < 0.0005) (Figure ). No patient in the clonidine and clonidine plus ropivacaine groups complained for tourniquet pain, indicating the success of the femoral block as a supplement of perioperative analgesia. On the contrary, all patients in the control group complained for tourniquet pain.
CAS pain between groups. The mean pain CAS score (mm) at rest in the Control, Clonidine, and Clonidine plus 0.2% Ropivacaine groups at 0, 2, 4, 6, 8, 10, 18, 24 h time points after surgery.
In the ward the mean pain CAS score in clonidine and clonidine plus ropivacaine groups was lower than in the control group (p < 0.0005), while at 4 and 6 hours postoperatively the mean pain CAS score in clonidine plus ropivacaine group was lower than in the clonidine group (p < 0.05), (Figure ).
According to the protocol, a rescue dose of 0.2 mg/kg nalbuphine was given as follows: In the clonidine plus ropivacaine group four patients required one rescue dose and one required 3 doses. In the clonidine group, 16 patients required one rescue dose (Figure ). In the control group 15 patients required 3 rescue doses of nalbuphine and 5 required 2 doses. However, nine of them required a rescue dose of 0.3 mg/kg, because of a pain CAS score more than 45 mm at 6 hours postoperatively.
Rescue doses of Nalbuphine. Rescue doses of Nalbuphine in the Control, Clonidine and Clonidine plus 0.2% Ropivacaine groups at 0 up to 24 h after surgery.
The sensory block in the distribution of all the area of the sciatic nerve or/the CPN, and in the area of the femoral nerve, in the clonidine plus ropivacaine group lasted 16.45 ± 5.81 hours, and 8.6 ± 2.6 hours respectively. No patient in the clonidine group presented sensory block.
Furthermore, most children of clonidine plus ropivacaine, and clonidine groups, eliciting plantar flexion or strong inversion of the foot presented better postoperative analgesia and required fewer rescue doses of nalbuphine compared to children eliciting dorsiflexion of the foot (Chi-Square = 18.66, p = 0.003).
None of the patients in clonidine, and clonidine plus ropivacaine groups presented motor block.
In the recovery, all the patients of clonidine and clonidine plus ropivacaine groups were calm versus 9 patients of the control group (p < 0.005). In the ward during the 24 hours postoperative observation period, 10 of the 20 patients of control group presented PONV once, but none in the clonidine/clonidine plus ropivacaine groups (p < 0.005).
In clonidine plus ropivacaine group 6 of the 22 patients were sedated (level 1) lasting one hour versus sedation level 0 in all patients of control and clondine groups. In this study, none of the patients presented side effects due to SLPB.
During the second postoperative day, the parents of children, of control, clonidine and clonidine plus ropivacaine groups expressed a satisfaction mean score of 7.50 ± 0.70, 9.74 ± 0.45, 9.73 ± 0.70 respectively (p < 0.0005) about the perioperative management of their children.