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30 de septiembre de 2006 |
| Original Text: Bipolar Resectoscope | ||||||||||||||||||||||||
"Bipolar Resectoscope: The future perspective of hysteroscopic." Authors: Luca Mencaglia *, Emmanuel Lugo, Cristiana Barbosa Introduction There are essentially two types of resectoscopes which differ in outer diameter: 7,5 mm and 9,2 mm. The 7.5 mm resectoscope should be used in case of narrow cervical canal or difficult dilatation, the 9,2 mm resectoscope allows to perform major surgery. 1 Electro surgery in hysteroscopy Biological tissue contains a more or less high concentration of electrolytes, making it sufficiently conductive to be treated by electro surgically. The thermal effect of high frequency current is used for separating (cutting) and coagulating tissue (desiccation of tissue). The high frequency currents must be used on the human since low-frequency currents can stimulate nerve and muscle cells in the currents flow due to electrochemical processes (electrolysis). These effects are small enough to be disregarded with frequencies above 100 kHz. 2 Monopolar or bipolar current system can be adopted: Monopolar Resectoscope: Bipolar Resectoscope: EquipmentThe new working element developed by Karl Storz System, the Autocon II 400 (Figure 1), is for use in laparoscopy, resectoscopy and open surgery. It can be equipped with four different HF output sockets: monopolar, bipolar, multifunction and neutral electrode sockets. The user can assign a socket with the following parameters: cutting mode, coagulation mode or cutting and coagulation activation type. A mode is characterized by different generator setting such as frequency, peak voltage, modulation etc. A total of 9 monopolar and 8 bipolar modes are available. However, each specific socket is only available for a part of these modes. The user can also assign the following parameters to a mode: power limitation cutting, cutting effect, power limitation coagulation or coagulation effect. Using bipolar system, in the Saline Time-C-Cut mode as the Saline Coagulation mode, the HF voltage form is unmodulated sinusoidal, the rated frequency is 350 kHz (at RL=500ohms) +/- 10%, the crest factor is 1.4, the rated load resistance is 50 ohms, the maxim HF peak voltage is 190 Vp, the number of power/effects are 8, the maxim power output 370 W+/- 20% and the parameter standard of use is effect setting 4 for cut and also effect setting 4 for coagulation. The average applied HF-power is approximately 130 Watts for resection. Its is important to point out that, this peak voltage are much lower compared with monopolar systems.
The bipolar components (Figure 2,3) are compatible of existing resectoscope (optics, sheath). The sheat designed by Karl Storz- Endoskope is electrically completely isolated, the current return direct via the return electrode, prevent a current flow via the sheath, guarantying a high level of safety. Karl Storz has available a variety of cutting loops (GP, GPV, GD, GDV) in 24 Fr., but for the market there are still other bipolar loops for resection in gynecology and urology under development.
Figure 2 (left). The bipolar element of the resectoscope. Figure 3 (right).
The direct current return via the electrode prevent a current flow via the sheath. In 2000, Loffer FD 7 , reported a preliminary experience with the Versa Point bipolar resectoscope in gynecology, using in 15 patients, vaporizing electrode in saline solution distending medium, showing be effective in the removal of sub mucous myomas. Golan et al 8 in 2001 reviewed outcomes of operative hysteroscopy, using bipolar electrical energy (Versa Point) in saline solution in 116 women with intrauterine pathology and they proposed this new technique to potential replacement of the monopolar resection. Furthermore many studies had demonstrated their benefits in urology. Recently Singh H et al 9 reported the utility of bipolar system in the transurethral prostate resection (TURP) with less postoperative dysuria. Wendt-Nordahl 10 et al underlined in 2004 the advantage of the bipolar system in TURP, with the Vista System, and stressed the theoretical benefit to avoid the risk of TUR Syndrome. Our preliminary experience in gynecology consist in 57 patients (Table I) treated by Karl Storz 26 Fr bipolar resectoscope and Autocon II 400 high frequency unit with parameters standard selected 180 (in effect 4) for cut and 120 (in effect 4) for coagulation. The resection loops are completely insulated from the sheath of the resectoscope and are reusable loops. Saline solution (NaCl 0,9%) was used as distension medium with no complications.
cm = centimeters Table 1. Bipolar Resection in 57 patients Cutting power and coagulation appears sensible better in comparison with monopolar resection. Especially the first cut in case of fibroid tissue doesn't give any problem, thanks to the plasma effect. Furthermore the vision during resection is not disturbed from the presence of air bubbles. We included in our series complex cases to evaluate the technical characteristics of the instruments, including an important number of uterine fibroids, that in some cases where more than 4 cm of size and G1 and G2 (partially or totally intramural localization). Results in terms of time of surgery, intra operatory bleeding, complete removal of the pathology were better if compared with traditional monopolar resection. (Fig. 4,5,6,7)
Conclusion In our experience and also in the analysis of the published data appears very clear that the bipolar resectoscope presents some advantages in comparison with the monopolar. The current flow through tissue is restricted to the area between the two electrode's loops that are under direct vision of the surgeon. Current can be regulated at all times and set to the lowest possible: optimal flow of current for minimally invasive treatment. The plasma effect of bipolar current allows better cut and coagulation. In the monopolar technique the current passes through many tissues outside the surgeons' visual control before it can return to the generator. 5,11 The risk of thermal injuries at distant organs or tissues, by direct contact of instruments, imperfection of insulation or diffusion of the electric current, is reduced in the bipolar technique. 12,13 It has minor risk of interference on other electronic equipments (ECG, pace makers and others) simultaneously connected to the patient. 5,14 Furthermore there is reduced stimulation of peripheral nerves including the obturator nerve, because no flow of current through the body of the patient. Distension media: Main concerns in urological and gynecological conventional monopolar resection are fluid absorption with hiponatremia, hipervolemia and glycine toxicity. This syndrome is very dangerous for the patient leading to neurotoxic coma and death in the worst cases. Most of the morbidities of the overflow syndrome are related to the use of hypotonic non electrolyte irrigation fluid. For this reason require close and continuous peri operative monitoring of the balance of distension medium by a nurse and frequent laboratory investigations. Bipolar resection system, permits resection using saline solution. The use of saline solution for distension media of the uterine cavity, is the principal advantage of this technology so avoid use of hypotonic non electrolyte solution that can cause fluid overload during the surgical procedure. Saline solutions is easily metabolized, is not toxic and can be used with higher quantity and it is also less expensive than conventional hypotonic non electrolyte solutions. Singh et al 9 in a bipolar versus monopolar TURP randomized controlled study reported a significant difference in serum sodium concentration post operatively. In bipolar TURP the change in serum sodium was -1.2 mEq/L (not different from preoperative serum Na concentration), whereas in the monopolar group the mean decrease was 4.6 mEq/L. In three patients serum Na was >125 mEq/L at risk of TUR syndrome. However also balance of distension medium using saline solution should be under control. Starkman and Santucci 20 retrospectively reviewed 43 undergoing TURP, 18 consecutive patients treated with the monopolar TURP and 25 with bipolar TURPs. These investigators found an unexpected case of hiponatremia and pulmonary edema in a bipolar TURP patient. Patel et al. also expressed concern for potential problems with hipervolemia and hiponatremia. They suggest warming the saline solution and emptying the bladder from time to time during surgery. In our experience no overflow syndrome occurs. Tissue alterations: Less bleeding during resection. Better visibility. Reduced costs: The outcomes of studies in gynecology and urology with bipolar system demonstrate its versatility and the possibility of rapid replacement of "old" monopolar system. The bipolar system is technically superior, cost-effectiveness and safer in comparison with the monopolar system. If we take in consideration also the medical-legal aspects, it will be very dangerous to maintain the old system, especially in case of complications. Preliminary findings of decreased morbidity using bipolar system using saline solution, force us to consider others factors involved in possible complications as duration of surgery as well as the experience of the surgeon. These variables must be included in our future investigations. However the decrease of "theorical risk" of overflow syndrome that give the bipolar system doesn't allows to avoid close peri operative monitoring of distension medium balance and laboratory investigations. Larger prospective randomized clinical trails examining cost-effectiveness and long-term outcome need to be performed, although it seems already very clear that this technology will replace in a near future the conventional monopolar electro surgery.
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