Electrovaporization as a treatment modality for transurethral resection ofthe prostate: Influence of generator type

Objectives. To study the influence of the electrosurgical generator on the vaporization efficacy during electrovaporization (EVAP) using different vap orization elements. Methods. Electrical properties of human prostatic (in vivo) and bovine myoc ardium (in vitro) tissue were measured under electroresection and electrova porization conditions. The effective output power of four different generat ors ("old generation" Force 4 and Force 40 and "new generation" Force 300 a nd Force FX) was measured at different impedance loads. In vitro, the coagu lation and vaporization capabilities of the electrosurgical generators in c ombination with resection and vaporization elements were studied on homogen eous tissue (bovine myocardium). Results. The electrical impedance of human prostatic tissue and bovine myoc ardium increases from 400 to 1000 Omega when coagulated. The effective outp ut power of the old generation electrosurgical devices depends strongly on tissue impedance. This implies that working on already coagulated tissue us ing such devices is not well controlled and not reproducible. By contrast, new generation electrosurgical devices correct for the higher impedance of coagulated tissue, thus delivering constant output power and corresponding tissue effects. Conclusions. For an effective application of the EVAP technique, the use of a new generation impedance independent electrosurgical unit is highly reco mmended. (C) 1999, Elsevier Science Inc. All rights reserved.