Complications of Lithotripsy

Definition

Extracorporeal shock wave lithotripsy (ESWL) is accomplished by the transmission of shock waves through the patient’s body to pulverize urinary calculi. Unlike second-generation lithotriptors, first-generation units require that the patient be immersed in a water bath ( Fig. 47.1 ). In addition to anesthetic risks, this unique environment exposes patients to potential complications from water immersion and the release of energy by the shock waves.

During ESWL a mechanically generated shock wave passes through water as a single pressure impulse. On reaching the patient, the wave passes through the patient’s tissues en route to the “target zone,” which is defined as the area that contains the calculus ( Fig. 47.2 ). Fluoroscopy is used to confirm that the urinary calculi remain in the target zone. When the shock wave encounters a different density, such as the urinary calculus, it releases energy to fragment the calculus into sandlike particles, which is the desired therapeutic effect. However, damage to other tissues or implanted mechanical devices can occur. To prevent cardiac arrhythmias, the lithotriptor can be synchronized to trigger the shock wave during the refractory period of the patient’s cardiac cycle. In certain patients, hydrostatic pressure created by immersion can significantly compromise cardiovascular and pulmonary function.