EFFECTS OF POWER AND ELECTRICAL-CURRENT DENSITY VARIATIONS IN AN IN-VITRO ENDOMETRIAL ABLATION MODEL

Objective: To investigate the thermal effects of electrical power and waveform on uterine tissue in vitro, using the gynecologic resectoscop e with a 2.5-mm roller-bar electrode. Methods: The power setting was i ncreased in a serial fashion using both the modulated or damped (coagu lating) and unmodulated or undamped (cutting) current to ablate endome trial uterine tissue, using a technique similar to that employed in cl inical situations. The power setting ranged from 20-75 W with the modu lated waveform and 40-160 W with the unmodulated waveform. Measurement s of tissue damage were made by staining for hematoxylin and eosin and the respiratory enzyme dehydronicotinamide adenine dinucleotide phosp hate diaphorase. Results: The amount of thermal injury present correla ted linearly with the amount of wattage used for either current. Regar dless of the power used, the maximum amount of injury into the myometr ium was 4.2 mm, representing 19% of the uterine wall thickness, well w ithin the limits of safety. Destruction to 3 mm of myometrium was achi eved significantly more often using an unmodulated waveform at greater than 90 W (chi2, P = .03). Conclusions: Although the correlation betw een power and tissue damage achieved statistical significance, the rel ationship was weak; less than 12% of the observed variation was attrib utable to increasing wattage. Power and waveform alone do not appear t o be clinically significant determinants of the amount of thermal inju ry occurring during endometrial ablation.