Effective Concentration of Lidocaine Plus Fentanyl for Caudal Block in Patients Undergoing Transrectal Ultrasound Guided Prostate Biopsy.

Objective. This study determined the effective concentration (EC) of lidocaine plus 75  μ g fentanyl for caudal block in patients undergoing transrectal ultrasound (TRUS) guided prostate biopsy. Methods. Consecutive male patients scheduled for TRUS guided prostate biopsy were enrolled. The mixed solution for caudal block contained lidocaine and 75  μ g fentanyl, in total 20 mL. The concentration of lidocaine was determined using the up-and-down method, starting at 0.8% (a step size of 0.1%). A successful caudal block was defined by no pain perception during biopsy. The EC50 of lidocaine for successful caudal block was calculated and side effects were evaluated. Results. A total of 23 patients were recruited. The EC50 of lidocaine for successful caudal block was 0.53%. Conclusions. Lidocaine of 0.53% combined with 75  μ g fentanyl resulted in excellent caudal block in 50% of male patients undergoing transrectal ultrasound guided prostate biopsy.