A pilot study of energy utilization patterns during different transurethral electrosurgical treatments of the prostate.

摘要

OBJECTIVES: During a prospective randomized study of prostatic and periprostatic heating during transurethral electrosurgical treatment, energy utilization was studied with respect to electrode configuration and prostate size. METHODS: Patients were stratified for gland volume (transrectal ultrasound [TRUS] 50 cc or less and more than 50 cc) and randomized to treatment either with loop resection (transurethral resection of the prostate [TURP]) or electrovaporization (transurethral electrovaporization [TUEVAP]. VaporTrode-Grooved Bar, CIRCON ACMI). Power was provided by a radiofrequency unit (Force FX, Valleylab) initially set at 150 W. A passive feed-through system was connected to the patient circuit to record current and voltage at 10 Hz during each activation of the cut mode in real time. RESULTS: Patients (6 per group) were well matched for prostate volume (P < 0.57) and operating time (P < 0.33). Power settings were also similar (120 to 190 W). Both total energy utilization (P < 0.025) and energy used per minute of treatment (P < 0.004) were greater for TUEVAP than for TURP. The higher energy deposition per unit time for TUEVAP was not associated with undesirable periprostatic heating. For TURP, more energy was used per unit time for each gram resected in small prostates than in larger glands. Comparing energy consumption per minute per cubic centimeter of prostate, we found a 2:1 ratio between TUEVAP and TURP in large prostates, which increased to 3.4:1 (P < 0.049) in small glands. CONCLUSIONS: For the same panel power settings, more energy is deposited at the tissue interface during TUEVAP than during TURP. This extra energy provides better surface hemostasis without undesirable deep heating and can be explained by the larger contact surface and contact time (slower speed of excursion) of the VaporTrode than a regular loop. The novel observation that more energy is required for small prostates during both treatments suggests that these glands have different electrical properties and higher tissue impedance than larger glands.