Prostatic desiccation: a preliminary report of laboratory and clinical experience

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 vaporizing-cutting (VC) electrodes recently developed for use in high-energy transurethral resection of the prostate (TURP).

MATERIALS AND METHODS

Four VC electrodes were assessed for their haemostatic 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 electrode was attached to a scanning system (developed previously) that allowed the electrode pressure on the tissue surface (in 3% sorbitol solution) and the running speed to be adjusted. The same generator was used with all devices. 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 reference. After completing the procedure, the surgical wound and the surrounding tissue were dissected out and the depth of the heat-affected zone (HAZ, defined as the desiccated zone) measured.

RESULTS

In pig muscle (stroke speed 5 mm/s) there was no significant difference in the depth of the HAZ between the four VC electrodes and the loop, or 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 300 W (P < 0.01). There were no significant differences in HAZ among the VC electrodes at any power level. In dog muscle in vivo (stroke speed 10 mm/s), the 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 TURP) (P < 0.01). There was no significant difference among the VC electrodes. In dog liver 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 at 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 muscle and liver in vitro, regular loops used at a higher power created a desiccation zone that was 70-80% of the depth created by the VC electrodes.

Efficacy of transurethral electrovaporization of the prostate with respect to standard transurethral resection

Transurethral electrovaporization of the prostate (TVP) has been introduced as an alternative to standard transurethral resection of the prostate (TURP) with lesser morbidity. However, the efficacy of this new technique has not been well known. To compare the results of standard TURP and TVP, 76 patients with symptomatic benign prostatic hyperplasia (BFH) were divided into two groups in a randomized clinical trial. Preoperative assessment included AUA Symptom score, maximum flow rates (Qmax), digital rectal examination, serum prostate specific antigen, and transrectal ultrasonography, with biopsy if the patient was randomized to vaporization. Transrectal temperature measurements and the hemoglobin concentration of the irrigation fluid were investigated in all the patients during the procedure. Although the transrectal temperature was higher in the TVP group (0.53-1.27 degrees C; mean 0.83 degrees C), no associated complication were determined. However, blood loss was significantly lesser than with TURP (340 mL v 60 mL). Two patients in the TURP group required blood transfusions, and one had sphincteric incontinence, whereas one postoperative retention, one reoperation with bladder perforation, and one sphincteric incontinence were seen in the TVP group. On the other hand, 12-month follow-up demonstrated that the uroflow rates improved in a similar manner. The Qmax increased in the TURP and TVP groups from 8.8 and 8.3 mL/sec to 19.6 and 17.2 mL/sec, respectively. The mean AUA Symptom Score decreased from 13.7 to 7.9 and 6.1 at 6 and 12 months, respectively. In the TVP group and from 14.6 to 7.3 and 7.0 at 6 and 12 months, respectively, in the TURP group. There were significant differences in the mean catheterization time (P < 0.0001) and hospital stay (P < 0.0001) in favor of TVP. Our results suggest that TVP is a safe and effective alternative treatment for symptomatic BPH.

Applicability of the new ITKA GSD Basic 250 electrosurgical unit to urologic endoscopic surgery, laparoscopic surgery and urologic open surgery

The purpose of the study was to assess the applicability of a new ITKA GSD Basic 250 electrosurgical unit (ESU) to urologic endoscopic surgery, laparoscopic surgery and open urologic surgery, its possible interference with videorecording and stray currents in healthy tissues. A new ITKA GSD Basic 250 ESU (test ESU) was used and compared to conventional ESU (Berchtold Elektrotom 390 as reference ESU). Experimental surgery was carried out on three female pigs, which underwent endoscopic, laparoscopic and open surgery. Altogether 29 patients underwent either endoscopic or open surgery with the test ESU. In experimental surgery, the ideal cutting and coagulation settings of the test ESU were in the range 15-25% for endoscopic surgery. In laparoscopic surgery, tissues were ideally resected and removed at 10-15% power settings. In open experimental surgery, the ideal power settings were 25-30%. In human surgery, the test ESU operated well at 25-35% power settings in endoscopic surgery, while in open surgery on humans the ideal settings were 25-35% in monopolar use and 20-25% in bipolar use. When used for endoscopic operations, the test ESU did not interfere with videorecording. Nor were any adverse effects seen in the surrounding tissues. The patients had neither early nor late complications. Histopathological findings revealed no differences in healing between the test ESU and reference ESU. Experimental and patient surgery showed the test ESU to be both safe and effective. It is suitable to be used in urologic endoscopic surgery, laparoscopic surgery and open urologic surgery. It does not interfere with videorecording or cause harmful stray currents in surrounding tissues. Power can be adjusted linearly and precisely. Low-power operation is also possible.

Applications of electrical energy to the prostate: an evolutionary perspective

PURPOSE

We review modern electrosurgical treatments for removing benign prostatic tissue based on an historical perspective of medical applications of electrical energy.

MATERIALS AND METHODS

We reviewed historical reports and landmark observations concerning the evolution of medical applications of electrical energy in the literature, with a special focus on the development of principles pertinent to the transurethral electrosurgical removal of prostate tissue.

RESULTS

Modern transurethral electrosurgery of the prostate in a fluid medium has been well founded on key electrosurgical principles. Traditionally, the best clinical results and the least complications have been obtained through an understanding of the important precepts of this form of energy. These precepts have included distinctions between the reliability of effect and safety with direct and alternating current, and how different tissue effects can be achieved, either with selective current modes (cutting and coagulating waveforms) or by varying the size and configuration of the active electrode and its application time.

CONCLUSIONS

This review chronicles the prominent role of electrosurgery in our efforts to debulk an enlarged prostate in patients with symptomatic voiding dysfunction. History reminds us that many of today's "new ideas" are merely updated variations on a theme, have often been tried before in a fashion by our predecessors and have for one reason or another fallen by the wayside. The conundrum of the perfect combination of electrosurgical variables that can fulfill our goal of making this an efficient and complication-free treatment continues to stimulate and challenge us as we move towards the next millennium.

Electrosurgical vaporization of the prostate in the canine model

OBJECTIVES

To investigate the histopathologic changes and heating patterns caused by electrosurgical vaporization of the prostate in the living canine model.

METHODS

Prostate electrosurgical vaporization was undertaken in the canine model. Temperatures within and near the prostate and of the irrigation fluid were measured during a single pass and during the creation of a vaporized cavity. The prostate and adjacent tissues were examined by gross and microscopic pathology.

RESULTS

Coagulation occurred deep to the vaporization zone for 1.38 to 1.44 mm for a single pass of the rolling cylinder and up to 2.52 mm for multiple passes. Thermometry revealed temperature increases of only 4 degrees C 5 mm away from the vaporization site. The largest temperature increases were found in the irrigation fluid as it passed through the prostatic fossa. Microscopic pathology revealed no damage to adjacent tissues.

CONCLUSIONS

Electrosurgical vaporization creates minimal deep heating and coagulation beyond the vaporized cavity. The majority of the heat is removed by the irrigation fluid.

Review: transurethral microwave thermotherapy in benign prostatic hyperplasia

The transurethral microwave thermotherapy (TUMT) method combines the principles of microwave radiative heating and conductive cooling to destroy tissue within the prostate while preserving the other structures of the lower urinary tract. The method is effective in benign prostatic hyperplasia (BPH), as demonstrated by laboratory and clinical studies. The ease of the 1-hour office treatment, the dramatic symptomatic improvement and reasonable uroflow rates that result, the preservation of sexual function, the apparent safety, and the durability of the result may mean that TUMT will introduce changes in the management of BPH as dramatic as those brought about in lithiasis management by ESWL.

Temperature measurements and histology of the canine prostate during transurethral hyperthermia

Intraprostatic temperature measurements during transurethral hyperthermia at 44.5C were obtained in 5 dogs. Temperatures were also recorded in the bladder neck wall and the rectal wall. After completion of the temperature measurements, hyperthermia was continued for 3 hours. The prostates were then removed and taken for histologic examination immediately after hyperthermia and 1 week and 1 month later. The mean temperatures obtained in the 5 canine prostates were 44.5 +/- 0.4C at the heating electrode; 43.8 +/- 0.4C at a distance of 3 mm. from the electrode; 42.6 +/- 0.5C, 40.8 +/- 0.4C and 39.4 +/- 0.5C, 6, 9 and 12 mm. from the heating electrode, respectively, in the right, prostatic lobe. Similar temperatures were measured in the left lobe. The thermal gradient in the prostatic tissue was therefore about 4C per 1 cm. On histology, hemorrhagic necrosis of the prostatic tissue adjacent to the urethra was found. These histologic changes were found as much as 5 mm. from the heating antenna (where the temperatures measured were above 43C). The findings of our study may have major clinical importance. We found that thermal energy above 43C provides enough penetration to cause tissue damage and be clinically effective in most patients, while the thermal gradient around the heating electrode of 4C per 1 cm. is steep enough to confine histologic damage within the prostate.

Interstitial temperature measurements during transurethral microwave hyperthermia

Microwave hyperthermia is presently being investigated as a treatment for alleviating the symptoms of urinary outlet obstruction associated with benign prostatic hyperplasia. Two clinical techniques using intracavitary microwave applicators are being evaluated for safety and efficacy at various institutions. The transrectal technique uses a directional microwave radiator that is inserted into the rectum adjacent to the prostate. The transurethral approach uses a symmetrically radiating applicator located within the prostatic urethra. Transrectal prostatic heating techniques require surface cooling to prevent hazardous temperatures in the intervening rectal mucosa. Since transurethral applicators radiate from within the prostatic urethra, heating is confined to the obstructive tissue immediately surrounding the applicator. Concern has been expressed regarding the possibility of thermal injury to the prostate and adjacent rectum during transurethral hyperthermia treatment. In this report we present interstitial temperature measurements of prostatic and rectal temperatures in 5 patients. Temperature was observed to decrease at a rate of about 6C/cm. outward from the applicator. No clinically significant temperature increase was observed beyond 1 cm, outside the prostatic capsule or in the rectal mucosa.