Altok M et al, 2016: Comparison of shockwave frequencies of 30 and 60 shocks per minute for kidney stones: a prospective randomized study.
Altok M, Güneş M, Umul M, Şahin AF, Baş E, Oksay T, Soyupek S.
Department of Urology, Faculty of Medicine, Süleyman Demirel University, Isparta, Turkey.
Department of Urology, Faculty of Medicine, Şifa University, Izmir, Turkey.
Abstract
OBJECTIVE: One of the factors that determines the treatment success of shockwave lithotripsy (SWL) is the frequency of the shockwaves during the procedure. This study compared the efficacy and pain perception of shockwave frequencies at 30 versus 60 shocks/min for kidney stones.
MATERIALS AND METHODS: From August 2013 to May 2015, 160 patients with solitary, radiopaque kidney stones were randomized to SWL at 30 shocks/min (group 1) or 60 shocks/min (group 2), with 80 patients in each group. The primary outcome measure was success rate at 3 months after the last SWL session. The secondary outcome measure was pain perception during the procedures.
RESULTS: Of the 160 randomized patients, data for a total of 148 patients (74 patients in group 1 and 74 patients in group 2) were analyzed, after the exclusion of the patients lost to follow-up or who required secondary intervention within 3 months. There was no statistically significant difference between the two groups in terms of the success rate at 3 months (68.9% vs 71.6%, p = .719). However, the mean visual analogue scale scores of all the sessions were significantly higher in group 1 than in group 2 (5.83 vs 4.06, p < .05). Stone location, especially the lower calyceal location, was the only significant negative predictor for success according to multivariate logistic regression analysis.
CONCLUSIONS: The success rate was similar between these two frequencies. However, pain perception was significantly higher at 30 than at 60 shocks/min.
Scand J Urol. 2016 Sep 27:1-6. [Epub ahead of print]
Comments 1
In this randomized comparison between patients treated with SWL frequencies of 30 and 60 per minute (0.5 and 1.0 Hz) the conclusion was that the low frequency was without advantage in terms of treatment results and patients’ pain experience. Any tissue damage was not analysed!
Interestingly the low frequency was associated with higher pain scores. The authors assumed that this was an effect of greater bubble expansion. Although that might be possible theoretically, my personal guess is that patients feel more uncomfortable when there is a longer interval between successive shockwaves.
It should be noted that all patients in this study were treated following i.m. administration of only 75 mg of diclofenac and no other analgesic. This apparently resulted in earlier termination of the treatment in a number of patients in Group 1 (0.5 Hz). It had indeed been of interest to know if the lower frequency had been more effective if the patients had been given more advanced pain treatment during SWL.
The bottom-line of the report is, however, that reducing shockwave frequency below 1 Hz does not make sense, at least in terms of the variables measured in this study. It is important to emphasize that any further studies of this kind definitely also need measurement of indicators of tissue damage.