The Use of Ungating with the Medstone Lithotriptor

Safety of ungated shockwave lithotripsy in pediatric patients

OBJECTIVE

Ungated extracorporeal shockwave lithotripsy (ESWL) in adults is associated with cardiac arrhythmias. We report on the safety and efficacy of this method for treatment of renal calculi in children.

PATIENTS AND METHODS

Children under 14 years with radio-opaque renal stones were treated by ungated ESWL. Pre-treatment plain radiographs and intravenous urography and post-treatment ultrasonography and plain films were used to follow up clearance of fragments. All children were monitored for arrhythmias.

RESULTS

Thirty-seven children (28 males, nine females) with a median age of 5 years (range 2-14 years) underwent 69 ungated ESWL sessions for renal calculi. Nineteen children had stones located in the left kidney, 17 had stones located in the right kidney and one child had bilateral renal stones. The stone size ranged from 6 to 25 mm (mean 9.9 mm). Shockwave number ranged from 800 to 3650 (mean of 2500 shockwaves per session). All children underwent lithotripsy with a gradual incremental energy increase from 14 to 20 kV. No patient had cardiac arrhythmias or other intra-procedural complications. No patient required conversion to gated ESWL. The overall stone-free rate was 86%.

CONCLUSION

The results suggest that ungated ESWL is safe in children under 14 years. The efficacy was comparable to that of gated ESWL from previously published series.

Ungated extracorporeal shock wave lithotripsy in children: an initial series

OBJECTIVES

Ungated extracorporeal shock wave lithotripsy (ESWL) is associated with cardiac arrhythmias in adults. However, the incidence of arrhythmias in children undergoing ungated ESWL has not been established. Therefore, we report on the safety and efficacy of ungated ESWL of renal calculi in children.

METHODS

We evaluated all patients younger than 18 years of age who were undergoing ungated ESWL of renal calculi. All patients were monitored for arrhythmias, along with other standard monitoring, by the anesthesiologist.

RESULTS

Eight consecutive children (three boys and five girls) between 3.5 and 17 years of age (median 13.5) underwent 10 ESWL procedures for renal calculi. Of the 10 stones, 9 were located in the left kidney and 1 was located in the right kidney. The stone size ranged from 5 to 19 mm. Six patients underwent 3000 shocks and 2 patients underwent 800 and 2200 shocks. All patients underwent lithotripsy with a gradual incremental energy increase from 17 to 24 kV, except for 1 child (maximum of 18 kV) because of the patient's age (3.5 years). No patient had cardiac arrhythmias or other intraoperative complications. No patient required conversion to gated ESWL. The overall stone-free rate was 90.0% as determined by abdominal radiography and renal/bladder ultrasonography.

CONCLUSIONS

The results of this initial series suggest that ungated ESWL is safe and efficacious in patients younger than 18 years of age. Additional studies are warranted to evaluate further the use of ungated ESWL in the pediatric population.

The effect of rate of shock wave delivery on the efficiency of lithotripsy

PURPOSE OF REVIEW

The potential mechanisms of a shock wave rate effect are reviewed here, together with a report on the results of in-vitro, in-vivo and clinical studies that have assessed the effect of altering the shock wave rate on stone breakage and tissue injury by shock wave lithotripsy.

RECENT FINDINGS

The vast majority of studies assessing shock wave rate have reported improved stone fragmentation and a reduction in shock wave lithotripsy-induced tissue damage with slower rates of shock wave delivery. However, the optimal shock wave rate has not been determined.

SUMMARY

Slower rates of shock wave lithotripsy appear to improve the efficiency of this approach and therefore this suggests the need for a randomized clinical trial to assess shock wave rate.

Cardiac arrhythmias with external fixed-rate signal generators in shock wave lithotripsy with the Medstone lithotripter

OBJECTIVES

To evaluate the incidence and outcome of cardiac arrhythmias associated with an external fixed-rate generator and the Medstone lithotripter with regard to stone location, anesthesia type, patient age, and gender.

METHODS

Data were obtained on 933 patients who underwent shock wave lithotripsy (SWL) with the Medstone lithotripter. Patients were randomly divided into two study groups, including those with pre-existing cardiac disease, hypertension, and cardiac medications. Group 1 (576 patients) were treated with the external fixed-rate signal generator (cardiac simulator). Group 2 (357 patients) underwent electrocardiogram-gated SWL (no simulator). All patients were monitored for arrhythmias during SWL. Patients who developed arrhythmias on the simulator were converted to gated SWL.

RESULTS

In group 1, 463 patients (80%) had no arrhythmias during treatment, whereas 113 patients (20%) developed cardiac arrhythmias (primarily premature ventricular contractions [PVCs]) and were successfully converted to gated SWL. Only 1 patient in group 2 (0.3%) had a documented arrhythmia (PVC). Group 1 patients who developed arrhythmias with a cardiac simulator were more likely to have renal rather than ureteral stones. Chi-square analysis showed a significant correlation between patients with and without arrhythmias in group 1 with regard to stone location (P <0.0001). In group 1, regional anesthesia, intravenous anesthesia, and general anesthesia had an arrhythmia rate of 14%, 27%, and 38%, respectively. The only patient in group 2 who developed arrhythmias was under general anesthesia. The differences between groups 1 and 2, with regard to anesthesia type and arrhythmia, were statistically significant (P <0.001). No patients required additional medical therapy or hospitalization for cardiac events, and all patients safely completed the SWL treatment.

CONCLUSIONS

With careful monitoring and adequate precautions, external fixed-rate signal generators are safe, effective methods for pacing the Medstone shock wave lithotripter and probably other extracorporeal shock wave lithotripters.