The reliability of epidural anesthesia for repeat ESWL: a study of changes in epidural compliance.

Changes in epidural compliance were investigated before and after extracorporeal shock wave lithotripsy (ESWL) in 11 outpatients. Epidural pressures were unchanged acutely by ESWL (p greater than 0.15). In contrast to previous reports of failures of epidural anesthesia in patients having repeat ESWL treatments, a review of our population of patients having repeat ESWL indicates that epidural anesthesia is reliable and not associated with any greater failure rate than for initial ESWL treatments. The difference between our results and previous reports of high failure rates is likely due to differences in anesthetic and surgical techniques such as: (1) use of air for loss-of-resistance when locating the epidural space, (2) differences in the time interval between ESWL treatments, and (3) frequency of use of epidural catheters.