More energy, same results: high energy settings do not improve the efficiency of dual energy lithotripsy during percutaneous nephrolithotomy.

INTRODUCTION AND OBJECTIVE: No prior in vivo clinical trial has investigated the effect of varying energy settings on the performance of a dual-energy lithotripsy. We prospectively evaluated various impact and frequency settings during PCNL procedures to achieve optimal fragmentation and extraction of large stones of varying density. METHODS: Four impact and frequency settings were chosen based on a prior in vitro study and applied sequentially for 1 min each in a randomized manner during PCNL for large renal calculi greater than 3 cm in 24 patients: 4 Hz + 100% impact, 4 Hz + 30% impact, 12 Hz + 100% impact, and 12 Hz + 30% impact. Suction and ultrasonic settings were kept constant. For each setting, all removed fragments were collected, weighed, and dried to quantify stone removal rates. Fragments were categorized based on particle size, < 2 vs. ≥ 2 mm. Extraction rates (g/min), were expressed as medians and interquartile ranges (IQR). Statistical comparisons used the paired Wilcoxon Signed-Rank test. A sub-analysis was conducted based on density (≥ 1000 HU). RESULTS: 24 patients were enrolled. Median stone burden was 36 mm (IQR 32-54) and HU was 1170 (IQR 944-1336). Median extraction rates, 0.50 g/min (IQR 0.24-0.93), 0.55 g/min (IQR 0.22-0.87), 0.40 g/min (IQR 0.22-0.89), and 0.48 g/min (IQR 0.30-0.69), respectively, were not statistically different (Fig. 1a). Particle size was not influenced by impact and frequency settings (Fig. 1b). Fragmentation and extraction efficiency of highly dense stones (HU ≥ 1000) were not influenced by settings (Fig. 2). There was no significant difference in fragmentation or extraction efficiency based on stone composition (primarily calcium-based vs. non-calcium-based). CONCLUSION: Increased frequency and impact settings do not improve the efficiency of a dual-energy lithotripsy for clearance of large or hard stones and are unnecessary.