【Abstract】 Objective To evaluate the efficacy and safety of dexmedetomidineropivacaine combination for caudal block in elderly patients which received transurethral resection of prostate surgeries. Methods This prospective, doubleblind clinical trial included 80 patients of American Society of Anesthesiologist Grade I and II in the age group of 6080 years which received selected transurethral resection of prostate surgeries. Patients were divided into ropivacaine group and dexmedetomidineropivacaine group. The ropivacaine group (Group R, n=40) was received 02% ropivacaine 25 ml. The dexmedetomidineropivacaine group (Group D, n=40) was received 02% ropivacaine 25 ml plus 05μg/kg dexmedetomidine. The hemodynamic changes, block characteristics which included time to onset of analgesia, maximum sensory analgesic level, time of sensory analgesia duration, and motor block scores (Bromage). Pain (NRS) and sedation (OAA/S) scores were documented at the 1th(T1), 6th(T2), 12th(T3), 18th(T4), 24th(T5) and 48th(T6) after the operation. Rescue analgesic consumption and time to the first dose of rescue analgesia for 48 h also were recorded. The other recordings included sideeffects (nausea and vomiting, bradycardia, hypotension and shivering) during 48h after the operation. Results Significant differences were observed in relation to duration of sensory block (35048 +/4979 min in Group R and 43385 +/5165 min in Group D［P＜0.05］), duration of postoperative analgesia (38563 +/6009 min in Group R and 49345 +/7317 min in Group D［P＜0.05］) and consequently low doses of rescue analgesia in Group D (8375 +/3279) as compared to Group R (6900 +/2687) (P＜0.05). No difference of Bromage scores between two groups was observed. After blocks, the HR and MAP of two groups decreased than before, especially the decrease of HR in group D compared with the group R(P＜0.05). The NRS scores were lower in Group D from 6h to 18h after the operation(P＜0.05). There was no difference in sedation scores between two groups (P> 0.05). The incidence of bradycardia and hypotension in two groups were not different significantly (125% in group R and 275% in group D) and (50% in group R and 175% in group D)(P 005). Conclusion These results suggest that, in elderly patients which receive transurethral resection of prostate surgeries, dexmedetomidine is an effective additive to ropivacaine for caudal block, which is associated with prolonged sensory block and postoperative analgesia, reduced demand for rescue analgesics when compared to plain Ropivacaine. The dose of 05 μg/kg is safe for elderly patients without hemodynamic and other adverse effect.