Conversion of the Electrohydraulic Electrode to an Electromechanical Stone Impactor: Basic Studies and a Case Report

AbstractA 3.3F electrohydraulic electrode (Wolf 2137.23) has been confined within a spring with a metal end cap, irrigated with water and covered with a 0.003-inch metal sheath (outside diameter 5F). The electrohydraulic lithotripsy discharge (Wolf Generator 2137.50) at El causes the metal cap to extend 3mm. at 1,500cm. per second and creates an impact pressure of 600 to 800 bar. Stone fragmentation efficiency of the electromechanical impactor was equivalent to unshielded electrohydraulic lithotripsy (gallstone 2.83mg. per pulse, struvite/apatite 1.41mg. per pulse, cystine 0.41mg. per pulse, uric acid 1.48mg. per pulse and 100% calcium oxalate monohydrate 0.10mg. per pulse).Studies of the discharge of the electromechanical impactor within the pig ureter showed that minimal ureteral submucosal edema and hemorrhage occurred at 300 shocks discharged at a single point, and disruption of the mucosa and partial injury to the muscle layer occurred after 600 shocks given at the site of a pinched pig ureter. Pushi...