How to prolong postoperative analgesia after caudal anaesthesia with ropivacaine in children: S-ketamine versus clonidine

Background: The aim of the study was to determine whether caudal S-ketamine or clonidine prolonged analgesia together with ropivacaine. Methods: Sixty-three boys, aged 1–5 years, who were undergoing minor surgery, were allocated in order to receive one of three solutions for caudal anaesthesia. Group R received 2 mg·kg–1 0.2% ropivacaine; group C, 2 mg·kg–1 0.2% ropivacaine + clonidine 2 μg·kg–1; and group K, 2 mg·kg–1 0.2% ropivacaine + S-ketamine 0.5 mg·kg–1. Results: Postoperative analgesia assessed by CHEOPS lasted 701 min in group K (P < 0.05) compared with 492 min in group C and 291 min in group R. There were no significant differences between the groups for incidence of haemodynamic and respiratory alterations, motor block or sedation. Conclusions: This study demonstrates that S-ketamine 0.5 mg·kg–1 when added to 0.2% caudal ropivacaine provides better postoperative analgesia than clonidine without any clinically significant side-effect.