[Obturator nerve block for transurethral surgery. comparing ropivacaine 0.75 % vs. prilocaine 1 %]

Obturator nerve block is used for transurethral resection of lateral bladder wall tumors to prevent adductor muscle spasm and associated complications. Therefore, the local anesthetic applied should provide an adequate motor blockade. Ropivacaine 0.75 % was compared to prilocaine 1 % and motor blockade assessment performed by the Medical Research Council (MRC)-scale.

40 patients (20 per group) scheduled for transurethral resection were randomized to either receiving 10 ml ropivacaine 0.75 % or prilocaine 1 % for direct obturator nerve block in a controlled user-blinded study. Motor block was assessed with the MRC-scale 5 and 10 minutes after local anesthetic injection followed by an assessment 120 and 180 minutes after surgery. Surgery was performed in equally distributed spinal or general anesthesia, intraoperative adductor spasm intensity was evaluated by surgeon's ranking.

Motor blockade intensity was significantly higher with ropivacaine 0.75 % at all time points of assessment. Intraoperatively, severe spasm only occurred in the prilocaine 1 %-group.

Ropivacaine 0.75 % is a more appropriate agent for direct obturator nerve block than prilocaine 1 %, providing a faster onset and a more intense and longer-lasting motor blockade. This may reduce surgical complications and facilitate early surgical re-intervention. In this study, MRC-scale was appropriate for motor blockade assessment in a peripheral nerve block.