Ropivacaine 0.5% administered via a femoral catheter: is the obturator nerve also blocked?

摘要

Weber et al. sought to determine the optimal dose of ropivacaine 0.5% for analgesia injected through a femoral catheter, and as a secondary endpoint the suc- cess rate of obturator nerve block. The authors found a very high rate of effective block of the obturator nerve (up to 95%). This is in contrast with the results found by Parkinson et al. We have some concerns regarding the observations of Weber et al. due to the limitations of their study design. First, threading a femoral catheter up to 12 cm is hazardous. Capdevila et al. demonstrated that threading the catheter 16 to 20 cm results in a correct placement close to the lumbar plexus in only 23% of the patients, emphasizing that the course of the catheter was unpredictable. Ritter was unable to demonstrate in cadavers, a femoral nerve sheath capable of conveying a solution - or a catheter - from the inguinal ligament to the lumbar plexus. Unfortunately, Weber et al. did not verify radiologically the position of the catheter tip, leaving some doubt regarding its position.