Nitrous oxide vs periprostatic nerve block with 1% lidocaine during transrectal ultrasound guided biopsy of the prostate: a prospective, randomized, controlled trial

PURPOSE: We compared the efficacy of Entonox (BOC Gases, Manchester, United Kingdom), a mixture of 50% nitrous oxide and oxygen, with periprostatic infiltration of 1% lidocaine to provide analgesia during transrectal ultrasound (TRUS) guided biopsy of the prostate. MATERIALS AND METHODS: The study included 235 consecutive men undergoing TRUS guided biopsy of the prostate for elevated prostate specific antigen or abnormal digital rectal examination. Patients were randomized to 3 groups, including group 1-84 controls who did not receive any form of analgesia prior to the procedure, group 2-75 who received periprostatic infiltration with 10 ml 1% lidocaine with biopsies performed 5 minutes after infiltration and group 3-76 who received Entonox for 2 minutes through a breath activated device prior to the procedure and thereafter according to patient preference. All patients were asked to indicate the level of pain experienced before and after the procedure on a 10 cm, nonnumerical, horizontal visual analog score. Results were analyzed using 1-way ANOVA. RESULTS: Mean patient age was 68.8, 64.9 and 65.2 years, and mean visual analog score was 2.9, 1.6 and 2.2 in groups 1 to 3, respectively. Patients in groups 2 (1% lidocaine infiltration) and 3 (Entonox) experienced significantly less pain during the procedure compared with group 1 controls (p <0.001 and 0.028, respectively). There was no statistical difference in pain scores between groups 2 and 3 (p = 0.08). CONCLUSIONS: Inhalation of Entonox or periprostatic infiltration with 1% lidocaine can be used for analgesia during TRUS guided biopsy of the prostate since each provides significant and similar pain relief.