Comparison of the depth of the desiccated zone with selected vaporizing-cutting electrodes: a basic study in animals

Objective To evaluate in an animal model the haemostatic efficacy of vapori zing-cutting (VC) electrodes recently developed for use in high-energy tran surethral resection of the prostate (TURP). Materials and methods Four VC electrodes were assessed for their haemostati c efficacy in the muscle and. liver of pigs (in vitro) and dogs (in vivo). The devices tested were the roller-cutting and Vapor Cut (Karl Storz GmbH, Germany); the Wedge (Boston Scientific Corp,, Boston, USA); and the Uroloop (Endocare Inc., Irvine, CA). In each the depth of the desiccated zone was compared with that produced by a standard cutting loop electrode. Each elec t-rode was attached to a scanning system (developed previously) that allowe d the elect-rode pressure on the tissue surface (in 3% sorbitol solution) a nd the running speed to be adjusted. The same generator was used with all d evices. The tissue (muscle or liver) was cut by running the electrode over the surface at 200, 250 or 300 W, with the loop electrode used as the refer ence. After completing the procedure, the surgical wound and the surroundin g tissue were dissected out and the depth of the heat-affected zone (HAZ, d efined as the desiccated zone) measured. Results In pig muscle (stroke speed 5 mm/s) there was no significant differ ence in the depth of the HAZ between the four VC electrodes and the loop, o r among the VC electrodes at any of the power levels tested. In pig liver ( stroke speed 5 mm/s), the roller cutting and Vapor Cut electrodes produced a thicker HAZ than the loop at all power levels tested (P<0.01) . The Wedge electrode produced a significantly thicker HAZ than the loop at 200 and 30 0 W (P<0.01). There were no significant differences in HAZ among the VC ele ctrodes at any power level. In dog muscle in viva (stroke speed 10 mm/s), t he roller cutting. Vapor Cut and Wedge electrodes produced a significantly thicker HAZ at 250 W than the loop at 150 W (the usual power for TURF) (P<0 .01). There was no significant difference among the VC electrodes. In dog l iver in vivo (stroke speed 10 mm/s), the roller cutting electrode produced a significantly thicker HAZ at 250 W than the loop at 150 W (P<0.01). Conclusions The present VC electrodes produced a thicker desiccation zone a t higher powers (200-300 W) than the standard loop at the usual power (150 W). The four VC electrodes produced a similar desiccation zone. With pig mu scle and liver in vitro, regular loops used at a higher power created a des iccation zone that was 70-80% of the depth created by the VC electrodes.