Ungated Medstone outpatient lithotripsy

Changing Patient Position Can Eliminate Arrhythmias Developing During Extracorporeal Shockwave Lithotripsy

INTRODUCTION

Extracorporeal shockwave lithotripsy (SWL) has a low complication rate. While serious complications are rare, cardiac arrhythmias, such as ventricular tachycardia, may occur. The etiology of these arrhythmias is poorly understood, but it appears to be due to stimulation of the heart by the shock waves.

OBJECTIVE

This study examines the effect of rotating the patient 15° to 20° when an arrhythmia occurs.

METHODS

Eight hundred nineteen patients were prospectively evaluated for arrhythmias during SWL. The initial patient position was dependent on the location of the stone and the body mass index (BMI) of the patient. If a sustained arrhythmia developed, treatment was withheld for 2 minutes and then recommenced. If the patient developed an arrhythmia again, the patient was rotated 15°-20° away from the original position and treatment recommenced.

RESULTS

Twenty patients developed significant arrhythmias during SWL. Arrhythmias occurred more frequently in patients with a lower BMI (p < 0.01), of younger age (p = 0.01), and with right-sided stones (p = 0.035). After the first rotation, 11 patients had no further arrhythmias, and 4 patients had a reduction of their arrhythmia to unsustained minor arrhythmias that did not require cessation of the treatment. The remaining five patients required a second repositioning. Three of these patients required gated SWL to abolish the arrhythmia.

CONCLUSION

Changing the position of the patient by rotating the patient by 15 to 20° can eliminate arrhythmias that develop during SWL.

Variables influencing the likelihood of cardiac dysrhythmias during extracorporeal shock wave lithotripsy

INTRODUCTION

Extracorporeal shock wave lithotripsy (ESWL) is a safe and effective treatment of upper urinary tract calculi. While serious side effects are rare, transient cardiac dysrhythmias (CD) may be associated with ESWL. The exact etiology of these events, which are often unpredictable, is poorly understood. Awareness of CD during ESWL and identification of risk factors for developing them could help clinicians predict and manage them safely and effectively. The current study examines selected variables to determine whether they may predispose individuals to developing CD during ESWL.

METHODS

We compared 16 patients who experienced CD during ESWL to 56 control patients. Cases and controls were compared with respect to several continuous and discrete variables, including age, pre-treatment heart rate, number of shocks received during treatment, energy setting of the lithotripter, gender, presence of a ureteric stent, previous ESWL and side being treated.

RESULTS

Cardiac dysrhythmias occurred more frequently in younger patients and in those being treated for right-sided stones. The other variables did not influence the likelihood of CD. All CD resolved promptly following conversion to electrocardiogram (ECG)-gating.

CONCLUSION

Younger age and right-sided treatment predisposed individuals to developing CD during ESWL. Careful ECG monitoring should be performed during treatment.

Extracorporeal shock wave lithotripsy in impacted upper ureteral stones: a prospective randomized comparison between stented and non-stented techniques

OBJECTIVES

To assess the need for pre-extracorporeal shock wave lithotripsy (pre-ESWL) stenting in management of impacted upper ureteral stones of size < or = 2 cm and to verify whether stenting would influence the success of therapy.

METHODS

Between 2007 and 2008, a total of 60 patients with solitary, radio-opaque impacted upper ureteral stones measuring < or = 2 cm were divided into 2 equal groups: a stented group with a Double-J stent fixed pre-ESWL and a non-stented group treated by in situ ESWL. All patients were treated by ESWL using Dornier Doli S lithotripter. Results were compared in terms of clearance rates, number of shock waves and sessions, morbidity, and incidence of complications. Pretreatment KUB (kidneys, ureters, and bladder) and intravenous pyelogram and post-treatment KUB were used to evaluate fragmentation and clearance.

RESULTS

Overall stone-free rate was 88.3%. No significant statistical difference was observed in stone-free rate between the stented and non-stented groups being 90% and 86.7%, respectively (P = .346). One session was required in 28.3% of patients, whereas multiple sessions were required in 71.7% of patients. No significant statistical difference was noted in re-treatment rate in the 2 groups. Patients in the stented group significantly complained of side effects attributable to the stent predominantly dysuria, urgency, frequency, and suprapubic pain.

CONCLUSIONS

ESWL is an effective and reasonable initial therapy in the management of impacted upper ureteral stones measuring < or = 2 cm. Pre-ESWL ureteral stenting provides no additional benefit over in situ ESWL. Moreover, ureteral stents are associated with significant patient discomfort and morbidity.

Eighteen-year experience with the Medstone STS lithotripter: safety, efficacy, and evolving practice patterns

OBJECTIVE

To evaluate trends in safety, efficacy, and practice patterns for shockwave lithotripsy (SWL) procedures performed during a 18-year period and correlate the findings with recent evidence-based practice guidelines.

MATERIALS AND METHODS

From January 1988 to June 2006, 66,819 SWLs were performed using the Medstone STS lithotripter in patients with radiologic evidence of stones in the kidney or ureter. Treatment characteristics, such as stone location and size, need of re-treatment, and final success rate were recorded. The procedures were further divided by year for statistical consideration. Statistical analysis was performed using Student t test; P < 0.05 was considered significant.

RESULTS

Overall SWL success rate was 85% (39,667/46,669), and the overall re-treatment rate was 7.2% (3,417/46,669). There was no significant change in the overall proportion of lower-pole calculi managed with SWL, although there was a significant decrease in the proportion of SWL used for lower calix stones larger than 16 mm in the time period after 2000 (P = 0.006). There was a steady increase in the number of procedures performed for renal calculi in other locations per year, in particular for intrarenal calculi smaller than 20 mm. Intrarenal stones larger than 30 mm decreased as a proportion of procedures per year (P = 0.048) There was no significant change in the proportion of upper and distal ureteral stones managed, corresponding to a solid plateau in the percentage of SWL performed per year.

CONCLUSION

Our study did not demonstrate an overall drop in SWL; however, it did show the interference of endoscopic procedures on two case scenarios. There was a significant decrease (P = 0.048) in SWL for renal stones larger than 30 mm, and the same trend was noted for lower calix stones larger than 15 mm (P = 0.06).

Impact of Shockwave Coupling on Efficacy of Extracorporeal Shockwave Lithotripsy

PURPOSE

To evaluate the impact of a slow gated treatment rate on the efficacy of extracorporeal shockwave lithotripsy (SWL).

PATIENTS AND METHODS

From August 1990 to July 2002, 40,462 SWL procedures were performed using the slow frequency electrocardiography (ECG)-gated lithotripter (82.5%) and fast frequency ECG-ungated (17.5%) modes for the Medstone STS lithotripter. Treatment characteristics, including the mode of SWL, location and size of the stone, re-treatment status, auxiliary procedures required, perioperative complications, and treatment outcomes, were recorded. The stone-free rate was reported by the treating physician on the basis of the finding of no residual stone fragments on a plain radiographic image.

RESULTS

The treatment rate for the slow mode was a mean of 79.6 shocks/min, while the rate for the fast mode was 120/min. The total procedure time was 47.0 minutes for the slow mode and 40.6 minutes for the fast. The overall stone-free rate was higher for slow (66.9%) than fast (63.6%) procedures (P < 0.001). The stone-free rate for 1- to 10-mm stones was higher for the slow procedures (75.7%) than the fast procedures (70.7%; P < 0.001). Upper-ureteral stones responded better to slow treatment in terms of stone-free rate (79.5% v 72.6%; P < 0.001), re-treatment rate (6.5% v 8.0%, P = 0.05), auxiliary-procedure rate (6.1% v 8.9%; P = 0.01), and efficiency quotient (71 and 62). There was no significant difference in complication rates overall between slow and fast treatment.

CONCLUSIONS

With a minimal increase in procedure time, greater efficacy can be obtained for the treatment of radiopaque stones with a slower shock-delivery rate. In particular, upper-ureteral calculi and calculi <10 mm benefit from a slower treatment rate.

Extracorporeal shock wave lithotripsy with a transportable electrohydraulic lithotripter: experience with >300 patients

OBJECTIVE

To review a multicentre experience of using a transportable lithotripter (STS-T, Medstone, Inc, Aliso Viejo, CA. USA) for treating patients with urolithiasis in all parts of the urinary tract.

PATIENTS AND METHODS

In all, 326 patients with a total of 370 stones were treated as outpatients with the STS-T lithotripter. All patients received a single shock wave lithotripsy treatment and were followed after 4-6 weeks in the outpatient clinic, the primary endpoint being to determine the efficacy (as defined by the stone-free rate). Secondary objectives included establishing a database of patient demographic information, stone characteristics, stone location, procedural endpoints, and complication rates.

RESULTS

In all there were 370 procedures, with a mean of 2394 shocks administered at an energy level of 24 kV. The mean treatment time was 51 min, excluding anaesthesia-induction time. The mean stone aggregate size was 8.2 mm; 62% of the stones were in the kidney while 38% were in various locations in the ureter. Of the treated stones, 90% had definite or probable evidence of fragmentation. The overall stone-free rate after one treatment with the STS-T was 52.8%. Of patients with residual fragments, most (61%) had fragments of <4 mm in aggregate diameter. The overall complication rate was 3.8%, the most common complication being postoperative pain.

CONCLUSION

The Medstone STS-T lithotripter was an effective device for treating urolithiasis in all parts of the urinary tract. This system had a high margin of safety, as shown by the low complication rate. With no apparent sacrifice of efficacy compared to first-generation or fixed (not transportable) second-generation devices, the Medstone STS-T represents an important advance in the development of a truly transportable lithotripter.

Shockwave frequency affects fragmentation in a kidney stone model

PURPOSE

To study the effect of altering shockwave frequency on the efficiency of stone fragmentation using the MFL 5000 spark-gap lithotripter.

MATERIALS AND METHODS

Standardized solid plaster stones, 12.0 +/- 0.5 mm in diameter, were fragmented at an energy setting of 20 kV. The shockwave frequencies tested were 60, 80, and 117 per minute. Stones were fragmented throughout the entire lifespan of the electrode, from 0 to >100% consumption, at each frequency tested. Electrode pressure output was studied for each frequency.

RESULTS

A greater number of shocks was required to fragment the plaster balls at higher frequencies (regression coefficient 1.93; p < 0.003). An inverse relation was found between the number of shocks necessary to break the stones and electrode consumption (regression coefficient -2.16; p < 0.001). The analysis of delivered pressure from the electrode failed to demonstrate a linear relation with frequency (regression coefficient -0.40; p < 0.728) or consumption (regression coefficient -1.11; p < 0.158).

CONCLUSIONS

The number of shocks required to fragment a stone is influenced in part by the frequency at which the shockwaves are delivered. Increasing the shockwave frequency from 60 to 117 per minute in this study caused a significant rise in the number of shocks required to break the stone. The pressure output of the electrode was similar at the frequencies tested, thus making the difference in stone fragmentation secondary to the mechanism of stone disintegration and not the function of the electrode.