Impact of type of anesthesia on efficacy of medstone STS lithotripter

To evaluate the impact of the type of anesthesia on treatment efficacy, using a comparison of general anesthesia (GEN) and monitored anesthesia care with intravenous sedation (MAC), for patients undergoing extracorporeal shockwave lithotripsy (SWL) on the Medstone STS lithotripter.

A case-control study was conducted of 660 patients treated from 1986 to 2002. General anesthesia and MAC were utilized in 330 procedures each. Case matching was performed for stone size, stone location, and body mass index. All lithotripter units were staffed by a rotating schedule of the same 10 SWL-certified radiologic technicians. Patient characteristics, treatment parameters, complications, repeat procedures, and secondary procedures were recorded. Stone-free success rates (no residual fragments) were reported by the treating physician on the basis of plain radiographs. Chi-square analysis was used to compare patients in the two groups.

The overall stone-free rate was better with GEN (67%) than MAC (55%; P = 0.04). Stone-free rates were not affected for stones

This study helps define that population that may benefit most from the use of GEN: those with stones >10 mm or in an upper calix. General anesthesia may decrease excursion of the calculus out of the focal area secondary to breathing or patient movement.