[The role of lubrication in transurethral electrical resection]. / Die Rolle des Gleitmittels bei der transurethralen Elektroresektion.

Transurethral resection inevitably leads to thermal as well as mechanical stress on the urethra, and it is important to reduce both. This can be achieved by using a suitable lubricant. Measurements in saline irrigation fluid as long as 30 years ago showed that the distribution of high-frequency current in the region of the urethra during transurethral electrical resection depends on the different resection systems, i.e. the varying placement of the neutral electrode. Application of a lubricant with appropriate conductivity makes it possible to avoid dangerous current surges in the region of the urethra. When it is used for reduction of the mechanical stress on the urethra, the consistency and amount of the lubricant used and also the frequency of application are important. Theoretically, even in the case of the so-called bipolar transurethral resection procedure in saline used today, the possibility that the electric current will cause thermal damage to the urethra is as great as when a conventional monopolar resection procedure using nonconductive irrigation fluid is performed.

Electrocautery: principles and practice.

We explain the basic physics of transurethral resection of the prostate (TURP). Modifications of electrodes or high-frequency units that should improve TURP are discussed. Finally, we introduce Coagulating Intermittent Cutting (CIC), which is a TURP using a modified high-frequency generator. Results of in vitro experiments and the first data from a multicenter trial are demonstrated.

Coagulating intermittent cutting. Improved high-frequency surgery in transurethral prostatectomy.

OBJECTIVES: Transurethral prostatectomy (TURP) is the gold standard in surgical therapy of symptomatic bladder outlet obstruction. TURP is characterised by immediate treatment success, due to the removal of obstruction combined with a long-lasting improvement of symptoms and voiding parameters. In spite of good long-term results of TURP, intraoperative blood loss produces morbidity. We investigated a blood-sparing cut using a new high-frequency technology. METHODS: (1) A standard high frequency generator was extended in its function by additional electronics. (2) The possibility of a blood-sparing cut using 'coagulating intermittent cutting' (CIC cocut BMP) was quantified ex vivo using a blood-perfused porcine kidney. Four cuts next to each other were performed through the parenchyma using a standard resectoscope with a standard loop. This was done with a commercially available generator and CIC cocut BMP. The blood loss was determined semiqantitatively. RESULTS: (1) In a first step 'coagulating cutting' with coagulating and cutting periods (10/94-- 08/96) was developed. During each cut, phases with predominant cutting effect alternate with coagulating phases of defined duration. As a disadvantage, operation time increased due to lower cutting speed. In a second step cutting combined with coagulation effect with high voltage pulses -- 'coagulating intermittent cutting' (08/96--06/97) -- was developed. In this technique, the output signal consists of a pulse-modulated sinusoidal voltage with high amplitudes. But gas bubbles impaired vision. This finally resulted in the 'coagulating intermittent cutting' with constant voltage pulses and control of pulse intervals (CIC cocut BMP, since 07/97 up to now). (2) Comparing the function of the high-frequency generators in vitro, the Wilcoxon test for paired samples revealed a significant reduction of the observed bleeding with the CIC cocut BMP (p = 0.002). CONCLUSIONS: 'Coagulating intermittent cutting' improves the gold standard of TURP with reduced blood loss. The procedure is feasible with a standard resection equipment. The already trained surgeon has no further learning cure, and teaching of classical TURP is maintained.

Coagulating intermittent cutting: improved high-frequency surgery in transurethral prostatectomy.

PURPOSE: Despite the good long-term results of transurethral resection of the prostate (TURP), intraoperative blood loss and TUR syndrome produce morbidity. Thus, TURP is still considered invasive therapy. Many minor invasive alternative treatment modalities have been developed in recent years. MATERIAL AND METHODS: To minimize the risk of bleeding, we have improved on the high-frequency technology. The output signals of commercially available high-frequency generators were modulated such that each cut results in an efficient coagulation zone in the tissue with excellent cutting quality. RESULTS: Laboratory and in vitro studies using porcine kidneys as well as clinical trials showed good cutting characteristics accompanied by a significant reduction of bleeding. As a result, blood transfusions were less necessary, TUR syndrome occurred less often, the indwelling catheter could be removed earlier in the postoperative period, and hospitalization time was reduced. CONCLUSIONS: We believe that this improved high-frequency technology, termed coagulating intermittent cutting, results in blood-sparing tissue resection and reduction of morbidity.

[Coagulating intermittent cutting. Improved high-frequency surgery in transurethral prostatectomy]. / Koagulierendes Intermittierendes Schneiden. Weiterentwicklung der Hochfrequenzchirurgie bei der TURP.

In spite of the high and lasting efficiency of transurethral prostatectomy, intraoperative blood loss results in increased morbidity in this procedure. This led to the development of many alternative treatment modalities in the last years. To minimize the risk of bleeding, we improved the high-frequency technology in several steps. To achieve this, the output signals of commercially available high-frequency generators were modulated to the effect that each cut results in an efficient coagulation zone in the tissue at excellent cutting quality. Laboratory and in vitro studies using porcine kidneys as well as clinical trials showed good cutting characteristics accompanied by a significant reduction of bleeding. As a result, blood transfusions were less necessary, the transurethral catheter could be removed earlier in the postoperative period, and hospitalization time was significantly reduced. In conclusion, the improved high-frequency technology in form of the "coagulating intermittent cutting" results in a blood-sparing tissue resection with a consecutive reduction of morbidity.

Optimization of high-frequency electrosurgery of the meniscus.

In an in vitro study of the sheep's meniscus, the possibilities to reduce the thermal tissue necrosis caused by high-frequency electrosurgery of the meniscus were studied. Under standardized conditions, machine-made sections through the meniscus were cut using electrodes of various thicknesses and different settings of the electric generator. The thermal tissue necrosis near the cut through the meniscus was determined using light microscopy and image analysis on the specimen stained according to Masson-Goldner. With a constant voltage of 250 V tissue necrosis was significantly less for electrodes of a diameter of 0.5 mm than for 1.5-mm electrodes (187.3 microns as compared with 368.0 microns). For electrosections carried out using a commercially available electrode with a low voltage of 250 V as well as with a power-controlled generator, tissue necrosis was also significantly less than with a constant high voltage of 395 V (181.4 microns and 210.2 microns as compared with 325.0 microns). Thus, an effective reduction of thermal tissue necrosis in arthroscopic partial meniscectomy is possible when thin electrodes and power-controlled generators are used.

[High-frequency dental surgery near metal reconstructions]. / Zahnärztliche Hochfrequenzchirurgie in der Nähe metallischer Rekonstruktionen.

Dental electrosurgery carries the risk of incidental contact between the active electrode and metallic restorations. So far, on-line measurements of basic physical parameters during dental electrosurgery have not been performed under realistic conditions. The aim of our experimental study in pig jaws was to describe the physical phenomena more closely. 86 teeth in the jaws of freshly slaughtered pigs received occlusal amalgam fillings. Using 3 different units electrosurgical procedures were performed adjacent to the fillings. Voltage, current, impedance and power output were registered using a computer-controlled measuring system with high temporal resolution and broad dynamic range. The impedances of the amalgam fillings ranged from 0.5 to 9 k omega, with half of them being in the lower range of 0.5 to 1.5 k omega. During contact to amalgam fillings the dental electrosurgical unit had a high power output. Contact to fillings with low impedance yielded a power output up to 50 W. The other two electrosurgical units were equipped with different power output control systems thus preventing high power output during contact to metallic restorations. In conclusion, dental electrosurgery should be improved by units with dynamic power output control.

[Cutting and coagulating with high frequency currents: electrophysical effects of application of HF-surgery in dentistry]. / Schneiden und Koagulieren mit Hochfrequenzströmen: Die elektro-physikalischen Effekte bei Anwendung der HF-Chirurgie in der Zahnheilkunde.

In HF-surgery the patient is part of the electric circuit. Often the surrounding of the patient and the dental surgeon himself are included in the electric circuit, especially if no neutral electrode is used. In the patients mouth metallic elements such as amalgam, gold crowns and other parts of metallic restorations influence the flow of the electric high frequency current, used for cutting and coagulating. Due to this very complex situation, sure and quick cutting without hazards for the patient is only possible, if the dentist understands the electro-physical principles of HF-surgery.

[Measurement of physical parameters in HF surgical techniques in dentistry]. / Messung physikalischer Parameter bei HF-chirurgischen Massnahmen in der Zahnheilkunde.

A method for measuring electrical parameters in dental electrosurgery and new data on this surgical technique are presented. A computer-controlled system which measures voltage, current, phase, power and impedance with high temporal resolution was applied to dentistry. Statistical analysis of many operations on freshly butchered pig jaws was performed. The impedance of oral soft tissues is higher during cutting, the power required smaller than stated in the literature. The influence of frequency, power-output control, anatomical structures, and metallic restorations on dental electrosurgery is discussed in detail.

Regulated high frequency diathermy for bipolar electrocoagulation--a new method for the treatment of carcinoma of the bladder.

In the endoscopic treatment of bladder cancer, especially for stages beyond T2, transurethral resection does not seem to be sufficient. The risk of bladder wall perforation, the possibility of incomplete resection, seeding of tumor cells and high recurrence rates support the former statement [6]. Results of a multicentre prospective randomised study have exemplified that irradiation with the Neodymium-YAG Laser has been a reasonable alternative in the therapeutic approach to bladder cancer [2]. Diathermy coagulation must produce a sufficiently deep, homogeneous and well demarcated tissue necrosis. The coagulation depth has to be adjustable and heat production during coagulation should not lead to bladder wall perforation and consequent damage to the bowel. These criteria were investigated using regulated bipolar high frequency diathermy. The innovation in this method is, that thermal side effects on the tissue, e.g. vaporisation and carbonisation are prevented by a protective relay with constant current flow. Animal experimental studies have shown that this method meets all postulated requirements and therefore clinical trials can proceed.

Controlled bipolar high-frequency coagulation for transurethral application: a new method for the destruction of urinary bladder tumors.

The coagulation of small bladder papillomas or of the resection base after transurethral resection by unipolar high-frequency current has turned out not to be sufficiently radical so far. There is no definite and reproducible correlation between the achieved biological effect. Bipolar high-frequency current produces the desired necrosis in the deeper layers of tissue. When providing the high-frequency generator with a new experimental automatic control equipment, reproducible deep and homogeneous necrosis of the tissue can be achieved without taking a great deal of time. Moreover, adherence of the probe and carbonization are prevented. First, the experiments had been carried out in vitro on livers of cattle and secondly, in vivo on canine livers. By the conventional unipolar high-frequency coagulation a reproducible and homogeneous necrosis cannot be achieved. With the regulated high-frequency coagulation, however, we are able to produce homogeneous tissue necroses up to a depth of 7 mm, the extension of which can definitely be assigned to the adjusted technical parameters. The electrodes do not adhere, since carbonization does not occur because of the automatic control. Premature interruption of the coagulation process, even if the generator is adjusted too high by mistake, can be considered a further advantage of this protective switch. A first clinical experience is reported.

[Results of local transurethral high frequency hyperthermia in bladder carcinoma (author's transl)]. / Ergebnisse der lokalen transurethralen Hochfrequenzhyperthermie beim Harnblasenkarzinom.

On the basis of controversial results from clinical use of hyperthermal irrigation of the bladder lumen published by various authors a procedure was developed for transurethral local high frequency hyperthermia using phantom experiments and experimental bladder tumors. Encouraging results from experiments on animals led to clinical use of this technique with pretreated recurring bladder tumors (n = 64) at various stages. Poorly differentiated tumors at higher stages responded especially well. Typical pathohistological findings induced by hyperthermia were in these cases extensive tumor-necroses, and as late finding stromahyalinoses. Permanent changes of tumorfree urothelium have not been observed. During the observation period up to the present (maximum 48 month) the 3-year-survival rate has been 92.5% (T1G2-3), 59.4% (T2G3) and 22.0% (T3G3).

High frequency current effects during transurethral resection.

Transurethral resection has been simulated electrically to detect the current pathways and locations of heat production inside the patient. Different electrical behavior was noted with instruments using electrically insulated or metal sheaths. Conductive lubricating jelly should be used with the metal sheath and non-conducting jelly should be used with the insulated sheath.

[The significance of the characteristics of lubricating jellies in use during transurethral prostate resections with metallic sheaths (author's transl)]. / Zur Frage des Gleitmittels bei der transurethralen Prostataresektion unter Verwendung von Metallschäften.

If a metallic sheath is used during a transurethral resection of the prostate with high-frequency currents, the lubricating jelly has to exceed a prescribed conductivity, in order to prevent dangerous current-density spots within the urethra. Furthermore, the mechanical behaviour of the lubricating jelly and the mode of its application have to be considered carefully.

[Capacitive effects during transurethral resections with high-frequency currents (author's transl)]. / Zur Frage der kapazitiven Leckströme bei der transurethralen Prostataresektion bei Verwendung von Metallschäften

The cutting probe of transurethral resection devices has to be fed through a line inside of the shaft. The capacitive high-frequency currents between this feeder and the shaft flow through the urethra and may cause destructive heat within the urethra if a metallic shaft is used. This paper shows that no danger is caused from these capacitive currents as long as the capacity between feeder and shaft is less than 120 pF.

[Electrial aspects of transurethral resection with high-frequency currents (author's transl)]. / Die transurethrale Prostataresektion mit Hochfrequenzströmen aus elektrotechnischer Sicht

With the help of electrical models the current-density distributions within the human body during transurethral resection have been measured for systems with various electrodes. The results lead to rules for avoiding mistakes.