Comparison of the effects of clonidine and ketamine added to ropivacaine on stress hormone levels and the duration of caudal analgesia

BACKGROUND: The purpose of this study was to compare the analgesic quality and duration of ropivacaine 0.2% with the addition of clonidine (1 microg.kg(-1)) with that of ropivacaine 0.2% and the addition of ketamine (0.5 mg.kg(-1)) to that of ropivacaine 0.2% and also compare the postoperative cortisol, insulin and glucose concentrations, sampled after induction and 1 h later following caudal administration in children. METHODS: According to the randomization, patients in the ropivacaine group (R; n = 25) received ropivacaine 0.2%, 0.75 ml.kg(-1); those in the clonidine group (RC; n = 25) received ropivacaine 0.2% 0.75 ml.kg(-1) plus clonidine 1 microg.kg(-1) and those in the ketamine/ropivacaine group (RK; n = 25) ropivacaine 0.2% 0.75 ml.kg(-1) plus ketamine 0.5 mg.kg(-1) (10 mg.ml(-1) concentration). Drugs were diluted in 0.9% saline (0.75 ml.kg(-1)) and prepared by a staff anesthesiologist not otherwise involved in the study. In all groups, the duration of analgesia, analgesic requirements, sedation and insulin, glucose, cortisol concentrations were recorded and statistically compared. RESULTS: There were no significant differences among the three study groups with respect to age, weight or duration of surgery. Caudal administration of clonidine 1 microg.kg(-1) or ketamine 0.5 mg.kg(-1) induced a longer duration of analgesia (P < 0.05) compared with ropivacaine alone. Insulin levels were increased and cortisol reduced in all groups. Glucose concentration was increased in all groups and statistically significant (P < 0.05). CONCLUSIONS: Addition of ketamine and clonidine to ropivacaine 0.2% 0.75 ml.kg(-1), when administered caudally in children, prolongs the duration of postoperative analgesia. The need for subsequent postoperative analgesic is also reduced. Caudal analgesia attenuates or allows partial changes to postoperative cortisol, insulin or blood glucose responses to surgery.