PD42-07 THE EFFECT OF CLEAVE TECHNIQUE AND LITHOTRIPSY DURATION ON LASER FIBER POWER OUTPUT

Abstract

INTRODUCTION AND OBJECTIVES: Efficient laser lithotripsy is dependent on laser fiber tip power output. Burnback degradation is a well-documented cause of decreased power output, which may increase operative time. Reusable fibers are cleaved to remove the degraded tip and restore power output. The rate of power output loss during lithotripsy after cleaving with various techniques is not known. Such information is necessary to determine the optimal cleaving frequency and technique. The purpose of this study is to evaluate power output degradation with increasing lithotripsy duration following various cleave techniques. METHOD(S): In this randomized, prospective, single-blinded study 330 calcium oxalate monohydrate calculi were fragmented in a ureteral tube model submerged in normal saline using 200 and 365 mm diameter Lumenis reusable fibers. A Dornier Medilas H20 Ho: YAG pulsed laser was utilized at 8 Hz and 800 mJ (6.4 W). Fibers were cleaved using a ceramic scissor, a straight Mayo scissor, a scribe pen cleave tool, a diamond cleave wheel, and a #11 blade scalpel. Power output was measured at baseline and subsequently at 1 min intervals during stone ablation up to 15 min by an investigator blinded to the cleave technique. One hundred,15 min trials were performed including 10 per cleave technique on each fiber diameter. Independent-samples Mann-Whitney U, Kruskal-Wallis, and homogeneity of variances tests were used for statistical analysis with a significance of p<0.05. RESULT(S): Both fibers showed similar ranked trends in initial power output: new fibers (6.54 W); ceramic scissor (6.20 W); scribe pen (5.95 W); scalpel (5.68 W); suture scissor (5.39 W); diamond wheel (4.74 W). Degradation analyses revealed a significant decrease of 0.85 W in the 200 mm fiber compared to the 365 mm fiber after 1 min (p<0.05). The mean power output of all cleave techniques in the 200 mm fiber decreased significantly by 0.73 W (13.25%) over the first 7 min (p<0.05), after which there was no further change. This constituted an average loss of 0.1 W (2.0%) per min, although the power decreased rapidly by 0.62 W (11.34%) over the first 4 min. The 365 mm fiber showed no significant decrease in power output (p=0.908). CONCLUSION(S): The ceramic scissor is the optimal device for cleaving between cases. Cleaving increased power output by only 11.34% for approximately 4 min in the 200 mm fiber therefore, these results do not imply a benefit to intra-operative cleaving to increase power output. The 365 mm fiber maintained a significantly higher power output over 15 min of lithotripsy, emphasizing greater durability compared to the 200 mum fiber for all cleave techniques.