Tissue Loss During TURP

1. No. 109 Tissue Loss During TURP Trenton Barrett, Melvyn Kuan, Dickon Hayne Introduction In clinical practice, the mass of chips retrieved after TURP with the bipolar Gyrus system seems less than would be expected after a resection using a monopolar system. A commonly proposed explanation for this phenomenon is that more tissue is lost during a bipolar resection (perhaps due to a process of vaporisation) than during a monopolar resection. There are no reports in the literature to confirm this assumption[1,2,3] Results A reduction in mass was seen in all resected tissue (fig. 2). The tissue resected with monopolar technology had a mean weight loss of 10.20g (9-13g). The tissue resected using bipolar technology had a mean weight loss of 10.25g (8.2-14g). Analysis using the Mann-Whitney U test was unable to demonstrate a statistically significant difference between the two groups. There was no significant change of weight in any of the control samples. Aim An experimental model was designed to determine whether there is a true difference in the amount of tissue loss during bipolar and monopolar resection techniques. Fig. 1 Experimental model Bovine skeletal muscle was resected ex vivo using either a monopolar or a bipolar electrosurgical system Methods Bovine skeletal muscle[4] was resected ex vivo (fig. 1) using either a bipolar (Gyrus PK Super Pulse, 5.15mm Olympus loop) or monopolar (Valleylab Force Triad, Storz 6mm loop) system. Monopolar and bipolar samples were resected in 500ml of 1.5% glycine and 0.9% saline respectively. The mass of each sample was measured pre and post resection and any change in weight was recorded. The experiment was run five times in each arm. For each experimental sample a control sample was soaked in either saline or glycine for 10 minutes to account for any weight change that may occur though absorption of fluid. The variable of loop size was accounted for by calculating the difference in length of wire and adjusting the bipolar results to assume a similar loop size. Standard clinical energy settings were used*. The resections were performed in a reproducible manner (300 swipes timed by metronome over 10 minutes) by a single operator[5,6]. g Fig 2. Weight loss consistency Despite variation in weight amongst tissue samples (blue columns) the mass of tissue lost after each resection was similar (red columns) This suggests reproducibility and a valid experimental model g g g g g Bipolar Monopolar  5.15mm   6mm  14 mm2 19 mm2 Fig. 3 Comparative loop sizes# The marginally smaller diameter of the Gyrus loop results in approximately 26% less volume per swipe Conclusions There is unlikely to be a significant difference in the amount of tissue loss during bipolar vs. monopolar TURP. This is the first experiment in the literature to investigate this question. The reduced specimen weight after bipolar TURP is likely real, but due to a reduced volume per swipe taken when using a Gyrus loop of marginally smaller diameter (fig. 3) rather than tissue loss. To resect an equal volume of adenoma, a surgeon operating using a bipolar Gyrus system needs to account for a smaller loop size by increasing either the rate or duration of resection compared to their monopolar technique. References Talic RF et al: Prospective Randomised Study of Transurethral Vaporisation Resection of The Prostate Using the Thick Loop And Standard transurethral Prostatectomy Urology 55: 886-890, 2000 Talic RF: Transurethral electrovaporization-resection of the prostate using the “Wing” cutting electrode: preliminary results of safety and efficacy in the treatment of men with prostatic outflow obstruction. Urology 53: 106 –110, 1999. Gilling PJ, Cass CB, Cresswell MD, et al: Holmium laser resection of the prostate: preliminary results of a new method for the treatment of benign prostatic hyperplasia. Urology 47: 48 –51, 1996. Lim LM. Patel A. Ryan TP. Stranahan PL. Fuchs Quantitative assessment of variables that influence soft-tissue electrovaporization in a fluid environment. Urology. 49(6):851-6, 1997 Jun. Narayan P, Tewari A, Croker B et al. Factors affecting size and configuration of electro-vaporization lesions in the prostate. Urology 1996; 47: 679±88 Einarsson OJ. Lyrdal F. Neidhardt FO The "shrinkage" of the prostate during transurethral resection BJU. 55(1):38-41, 1983 * Valleylab Force Triad 120 watt pure, Gyrus PK Super Pulse 180 watt ‘Vaporpulse’ mode # as per manufacturer specifications Poster presentation sponsor