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A computer based, temperature controlled bipolar electrocoagulation system
OBSTETRgS ELSEVIER
European Journal of Obstetrics & Gynecology and Reproductive Biology 68 (1996) 119-122
GYNECOLOGY
A computer based, temperature controlled bipolar electrocoagulation system K . K a t o *a, K. Biihler a, C. K l e s s e n b, R . K o c h c, A . E . S c h i n d l e r a aDepartment of Obstetrics and Gynecology, University of Essen, Hufelandstrasse 55, 45122 Essen, Germany bDepartment of Anatomy, University of TfLbingen, Tiibingen, Germany CMHT Medical High Tech GmbH, OberrimsingenGermany Accepted 3 May 1996
Abstract
Objective: To reduce complications during electrocoagulation particularly injury of other organs, a computer based, temperature controlled bipolar coagulation system has been developed. Under this system temperature in the tissue is kept between 60°C and 95°C during coagulation. A real time graphic display provides the surgeon with an actual temperature at the tip of the forceps during coagulation. Study design: Rabbit uterine horns were coagulated at 900C and were examined histologically and histoehemicailyat 6 weeks after coagulation. Results: Electrocoagulation at 90°C induced a total loss of LDH activity in the tissue. Lumen of the uterus was completely occluded when examined 6 weeks later. Conclusion: This system with low temperature is sufficient for homogenous coagulation of the tissue. Keywords: Electroeoagulation; Bipolar coagulation; Hemostasis ; Adhesions; Endometriosis; Laparoscopic surgery
1. Introduction
2. Materials and methods
Electrocoagulation became an indispensable tool for surgeons. For the gynecologists, it is a quite useful technic for hemostasis, lysis of adhesions or coagulation of endometriosis at laparoscopic surgery. Tubal sterilization is another frequent indication of electrocoagulation [11. Introduction of bipolar electrocoagulation has brought a great improvement in this method, but still a variety of complications related to this technic are reported [2]. Among these complications injury of other organs is the most serious problem, particularly when an injury of bowel or ureter is left unnoticed during laparoseopy [3,41. We have developed a computer based, temperature controlled bipolar electrocoagulation system to reduce these risks, in which temperature in the tissue is measured in real time. This temperature is demonstrated on a graphic display during the procedure.
2.1. Coagulation system
* Corresponding author, Tel.: +49 201 7232440; fax: +49 201 7235962.
Fig. 1. Tip of the forceps. A microthermoclement is assembled in the upper part of the forcps.
The tip of the coagulation forceps is shown in Fig. 1. The forceps is 5 mm in width and has blunt jaws at the top, so that the tissue will not slip out from the forceps. The actual temperature of tissue is measured continuously by means of a microthermoelement, which is assembled in the upper part of the forceps. The temperature can be adjusted between 40°C and 95°C. The level
0301-2115/96/$15.00 © 1996 Elsevier Science Ireland Ltd. All rights reserved PII S0301-2115(96)02474-8
120
K. Kato et aL /European Journal of Obstetrics & Gynecology and Reproductive Biology 68 (1996) 119-122
of radiofrequency current is regulated by an automatic feedback mechanism, so that the target temperature is reached quickly, usually within a few seconds, and is kept constant during the coagulation. These changes in temperature and current power are displayed in real time on the monitor of a personal computer. A high frequency generator (COAG-T: MHT Medical High Tech, Oberrimsingen, Germany) with output power of 50 W into a 100-fl load and radiofrequent currency at 500 KHz was chosen in this study for the safety purpose to prevent a lateral energy spread during coagulation [5,6]. This radiofrequency current is relatively low. Although the lowest frequence used for electrocoagulation is almost 200 KHz, most of the systems use 1-3 MHz and some systems in ophthalmology have adapted up to 12 MHz.
2.2. Coagulation materials Uterine horus of five mature female New Zealand rabbits were coagulated through either a laparotomy or a laparoscopy under anesthesia. Rabbit uterine horns are known to have a similar structure to that of human fallopian tube [7]. These uterine horns were coagulated at 90°C for 30 s and their healing processes were observed histologically and histochemically 6 weeks later.
2.3. Histochemistry of lactate dehydrogenase (LDH) Activity of LDH in the tissue was examined according to the methods of Peerse [8]. This enzyme was selected after preliminary experiments with different histochemical stainings, because it is highly sensitive to electrocoagulation. LDH activity in the tissue reflects exactly the degree of tissue damage after coagulation.
°C/watt 100-
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]
8070605040302010-
I ' ~ ~
,
10
i
20
i
30
,
40
i
50
*
60
|
TO
i
80
i
90 seconds
100
Fig. 2. Temperature and radiofrequency current curves during and
after coagulationat 90°C for 30 s. At the point A the generatorwas shut off (end of coagulation) and the temperature returned to body temperature at the point B.
3. Results
Typical changes in temperature and radiofrequency current during coagulation at 90°C are shown in Fig. 2. The temperature elevated to 90°C in 6 s, and once it reached the target temperature, it stayed fairly constant until the end of coagulation. The current power was downregulated when the target temperature was reached. A minor change in tissue temperature raised the current power immediately (at 13 s in Fig. 2), so that the temperature was kept within ± 3°C during the procedure. When the generator was shut off, the forceps cooled down rather slowly, taking about 70 s to return to the body temperature. Rabbit uterine horn has similar LDH activity as human fallopian tube (Fig. 3a). Electrocoagulation at 90°C was sufficient to induce a total loss of LDH activity in the tissue (Fig. 3b). When the uterine horn was examined 6 weeks later, the lumen of the uterus was completely occluded (Fig. 3c). Although LDH activity was observed in the muscle, no activity was seen in the luminal epithelium. The histology also showed a complete occlusion of the uterine horn (data not shown). 4. Discussion
Application of heat in medicine is not a new idea. In ancient Egypt heated oil was already used for this purpose. According to the development of electrotechnical instruments in this century, a monopolar high frequency current was first applied for laparoscopic surgery. In the monopolar system an electric current flows from the coagulation forceps to a neutral electrode through the patient's body surface and the extent of coagulation site is hardly controlled. Development of bipolar coagulation system is a hallmark for laparoscopic surgery, in which a high frequency current flows only between the arms of the coagulation forceps or tweezers. This allows a smaller and controlled coagulation field at a target organ and it may reduce the risk of injury of other organs, particularly bowel and ureter. A new bipolar electrocoagulation system has been developed to reduce these risks further. This system is originally designed for the use in neurological surgery, where very fine thermocoagulation is an utmost requirement; an overheating may induce haemorrhage and carbonization of the brain tissue easily [9]. An advantage in this temperature controlled coagulation system is a direct measurement of the tissue temperature at the tip of forceps with a microthermoelement. A surgeon can monitor the temperature as well as the level of frequency current on the graphic display during the procedure. Furthermore, if the forceps touches surrounding tissues during coagulation, temperature at the forceps decreases and a display demonstrates this change, so that the surgeon recognizes it immediately.
K. Kato et al./ European Journal of Obstetrics & Gynecology and Reproductive Biology 68 (1996) 119-122
121
Fig. 3. LDH activity in rabbit uterine horns. (a) Normal uterine horn before coagulation ( x 83): (b) immediately after coagulation at 90°C for 30 s (× 106~; (c): 6 weeks after coagulation at 90°C for 30 s (× 106~. The lumen of uterine horn was occluded completely.
122
K Kato et al. /European Journal of Obstetrics & Gynecology and Reproductive Biology 68 (1996) 119-122
These data can be printed out as a part of an operation report or they can be stored in a hard disk or a floppy disk and reproduced for the later use. A tissue impedance regulated coagulation system has an advantage in a microinstrument [10], in which more sensitive electrical control is required for a pinpoint coagulation. In addition, no thermal sensor can be built in the fine tip and monitoring of the tissue temperature during coagulation is not possible. For this reason a temperature controlled coagulation system has more advantages than has a tissue impedance regulated system for laparoscopic surgery, particularly for tubal sterilisation. The tissue temperature was set at 90°C in this study. The purpose of the electrocoagulation is a homogenous coagulation of the tissue. With a conventional electrocoagulation system, in which the tissue temperature cannot be regulated, we often find that the fallopian tube as well as the mesosalpinx beneath the tube are completely burned out. Actually, coagulation of protein begins at about 60°C [5] and a temperature of much higher than 100°C at a coagulation site is not always necessary. Histological and histochemical examinations on rabbit uterine horns in the present study confirm this theory. Coagulation at 90°C was sufficient to induce complete vanishment of LDH activity, and a total occlusion of the lumen was achieved when it was examined 6 weeks later. It has been shown that a temperature of 90°C is sufficient for coagulation in a laparoscopic appendectomy [11]. Experimentally induced endometriosis was also successfully coagulated at 85°C [12]. In addition, sticking of the forceps to the tissue becomes less marked at a temperature below 120°C [13]. This lower setting of temperature has been used also in dermatologic surgery [14]. It should be emphasized that the forceps needs a long cooling time. The forceps reaches up to 300°C in a conventional coagulation system [6]. Once the forceps has such a high temperature, it remains at a dangerous temperature even after the generator is shut off. Laparoscopists pay attention not to touch other organs during coagulation, but very often they pay less atten-
tion after coagulation, while the forceps is still at a high temperature. Low temperature at the coagulation site also reduces this risk.
Acknowledgement Supported by a grant of the German Ministry for Research and Technology (BMFT)
References [1] Population Reports, Voluntary female sterilization: number one and growing. 1990; Series C, Number 10: 1-23. [2] Haney AF. The risks/benefits of laparoscopic cautery for endometriosis. Fertil Steril 1991; 55: 243-245. [3] Levy BS, Sonderstrom RM, Dail DH. Bowel injuries during laparoscopy: gross anatomy and histology. J Reprod Med 1985; 30: 168-172. [4] Gomel V, James C. lntraoperative management of ureteral injury during operative laparoscopy. Fertil Steril 1991: 55: 416-419. [5] Reidenbach HD. Hochfrequenz- und Lasertechnik in der Medizin. Berlin: Springer Vertag, 1983. [6] Semm K. Physical and biological considerations limitating against the use of endoscopically applied high-frequency current in the abdomen. Endoscopy 1983; 15: 282-288. [7] Kastendieck E, Mestwerdt W. Tierexperimentelle und klinische Aspekte der laparoskopischen Tubensterilisation. Geburtsh Frauenheiik 1973; 33: 971-978. [8] Peerse AGE. Histochemistry. Edinburgh: Curchill Livingston, 1972. [9] Moringlane JR, Koch R, Sch/ifer H, Ostertag CB. Experimental radiofrequency (RF) coagulation with computer-based on line monitoring of temperature and power. Acta Neurochir 1989; 96: 126-131. [10] Patil AA, Yamanashi W. Electroconvergent cautery. Neurosurgery 1994; 35: 785-787. [11] Waleezek H, Roeknagel St, Hegelmaier Ch, W61k G. Temperaturentwicklung bei bipolarer Hochfrequenzcoagulation am Appendixstumpf. Chirurgia 1993; 64: 1036-1039. [121 Kato K, Biihler K, Schindler AE. Electrocauterization in rats of experimentally induced endometriosis at a low temperature. Hum Reprod 1995; 10: 2423-2426. [13] Bergdahl B, V,~llfors B. Studies on coagulation and the development of an automatic computerized bipolar coagulation. J Neurosurg 1991; 75: 148-151. [14] Bergdahl B, Stenquist B. An automatic computerized bipolar coagulator for dermatologic surgery. J Dermatol Surg Oncol 1993; 19: 225-227.
European Journal of Obstetrics & Gynecology and Reproductive Biology 68 (1996) 119-122
GYNECOLOGY
A computer based, temperature controlled bipolar electrocoagulation system K . K a t o *a, K. Biihler a, C. K l e s s e n b, R . K o c h c, A . E . S c h i n d l e r a aDepartment of Obstetrics and Gynecology, University of Essen, Hufelandstrasse 55, 45122 Essen, Germany bDepartment of Anatomy, University of TfLbingen, Tiibingen, Germany CMHT Medical High Tech GmbH, OberrimsingenGermany Accepted 3 May 1996
Abstract
Objective: To reduce complications during electrocoagulation particularly injury of other organs, a computer based, temperature controlled bipolar coagulation system has been developed. Under this system temperature in the tissue is kept between 60°C and 95°C during coagulation. A real time graphic display provides the surgeon with an actual temperature at the tip of the forceps during coagulation. Study design: Rabbit uterine horns were coagulated at 900C and were examined histologically and histoehemicailyat 6 weeks after coagulation. Results: Electrocoagulation at 90°C induced a total loss of LDH activity in the tissue. Lumen of the uterus was completely occluded when examined 6 weeks later. Conclusion: This system with low temperature is sufficient for homogenous coagulation of the tissue. Keywords: Electroeoagulation; Bipolar coagulation; Hemostasis ; Adhesions; Endometriosis; Laparoscopic surgery
1. Introduction
2. Materials and methods
Electrocoagulation became an indispensable tool for surgeons. For the gynecologists, it is a quite useful technic for hemostasis, lysis of adhesions or coagulation of endometriosis at laparoscopic surgery. Tubal sterilization is another frequent indication of electrocoagulation [11. Introduction of bipolar electrocoagulation has brought a great improvement in this method, but still a variety of complications related to this technic are reported [2]. Among these complications injury of other organs is the most serious problem, particularly when an injury of bowel or ureter is left unnoticed during laparoseopy [3,41. We have developed a computer based, temperature controlled bipolar electrocoagulation system to reduce these risks, in which temperature in the tissue is measured in real time. This temperature is demonstrated on a graphic display during the procedure.
2.1. Coagulation system
* Corresponding author, Tel.: +49 201 7232440; fax: +49 201 7235962.
Fig. 1. Tip of the forceps. A microthermoclement is assembled in the upper part of the forcps.
The tip of the coagulation forceps is shown in Fig. 1. The forceps is 5 mm in width and has blunt jaws at the top, so that the tissue will not slip out from the forceps. The actual temperature of tissue is measured continuously by means of a microthermoelement, which is assembled in the upper part of the forceps. The temperature can be adjusted between 40°C and 95°C. The level
0301-2115/96/$15.00 © 1996 Elsevier Science Ireland Ltd. All rights reserved PII S0301-2115(96)02474-8
120
K. Kato et aL /European Journal of Obstetrics & Gynecology and Reproductive Biology 68 (1996) 119-122
of radiofrequency current is regulated by an automatic feedback mechanism, so that the target temperature is reached quickly, usually within a few seconds, and is kept constant during the coagulation. These changes in temperature and current power are displayed in real time on the monitor of a personal computer. A high frequency generator (COAG-T: MHT Medical High Tech, Oberrimsingen, Germany) with output power of 50 W into a 100-fl load and radiofrequent currency at 500 KHz was chosen in this study for the safety purpose to prevent a lateral energy spread during coagulation [5,6]. This radiofrequency current is relatively low. Although the lowest frequence used for electrocoagulation is almost 200 KHz, most of the systems use 1-3 MHz and some systems in ophthalmology have adapted up to 12 MHz.
2.2. Coagulation materials Uterine horus of five mature female New Zealand rabbits were coagulated through either a laparotomy or a laparoscopy under anesthesia. Rabbit uterine horns are known to have a similar structure to that of human fallopian tube [7]. These uterine horns were coagulated at 90°C for 30 s and their healing processes were observed histologically and histochemically 6 weeks later.
2.3. Histochemistry of lactate dehydrogenase (LDH) Activity of LDH in the tissue was examined according to the methods of Peerse [8]. This enzyme was selected after preliminary experiments with different histochemical stainings, because it is highly sensitive to electrocoagulation. LDH activity in the tissue reflects exactly the degree of tissue damage after coagulation.
°C/watt 100-
-
,o ~-.__.
]
8070605040302010-
I ' ~ ~
,
10
i
20
i
30
,
40
i
50
*
60
|
TO
i
80
i
90 seconds
100
Fig. 2. Temperature and radiofrequency current curves during and
after coagulationat 90°C for 30 s. At the point A the generatorwas shut off (end of coagulation) and the temperature returned to body temperature at the point B.
3. Results
Typical changes in temperature and radiofrequency current during coagulation at 90°C are shown in Fig. 2. The temperature elevated to 90°C in 6 s, and once it reached the target temperature, it stayed fairly constant until the end of coagulation. The current power was downregulated when the target temperature was reached. A minor change in tissue temperature raised the current power immediately (at 13 s in Fig. 2), so that the temperature was kept within ± 3°C during the procedure. When the generator was shut off, the forceps cooled down rather slowly, taking about 70 s to return to the body temperature. Rabbit uterine horn has similar LDH activity as human fallopian tube (Fig. 3a). Electrocoagulation at 90°C was sufficient to induce a total loss of LDH activity in the tissue (Fig. 3b). When the uterine horn was examined 6 weeks later, the lumen of the uterus was completely occluded (Fig. 3c). Although LDH activity was observed in the muscle, no activity was seen in the luminal epithelium. The histology also showed a complete occlusion of the uterine horn (data not shown). 4. Discussion
Application of heat in medicine is not a new idea. In ancient Egypt heated oil was already used for this purpose. According to the development of electrotechnical instruments in this century, a monopolar high frequency current was first applied for laparoscopic surgery. In the monopolar system an electric current flows from the coagulation forceps to a neutral electrode through the patient's body surface and the extent of coagulation site is hardly controlled. Development of bipolar coagulation system is a hallmark for laparoscopic surgery, in which a high frequency current flows only between the arms of the coagulation forceps or tweezers. This allows a smaller and controlled coagulation field at a target organ and it may reduce the risk of injury of other organs, particularly bowel and ureter. A new bipolar electrocoagulation system has been developed to reduce these risks further. This system is originally designed for the use in neurological surgery, where very fine thermocoagulation is an utmost requirement; an overheating may induce haemorrhage and carbonization of the brain tissue easily [9]. An advantage in this temperature controlled coagulation system is a direct measurement of the tissue temperature at the tip of forceps with a microthermoelement. A surgeon can monitor the temperature as well as the level of frequency current on the graphic display during the procedure. Furthermore, if the forceps touches surrounding tissues during coagulation, temperature at the forceps decreases and a display demonstrates this change, so that the surgeon recognizes it immediately.
K. Kato et al./ European Journal of Obstetrics & Gynecology and Reproductive Biology 68 (1996) 119-122
121
Fig. 3. LDH activity in rabbit uterine horns. (a) Normal uterine horn before coagulation ( x 83): (b) immediately after coagulation at 90°C for 30 s (× 106~; (c): 6 weeks after coagulation at 90°C for 30 s (× 106~. The lumen of uterine horn was occluded completely.
122
K Kato et al. /European Journal of Obstetrics & Gynecology and Reproductive Biology 68 (1996) 119-122
These data can be printed out as a part of an operation report or they can be stored in a hard disk or a floppy disk and reproduced for the later use. A tissue impedance regulated coagulation system has an advantage in a microinstrument [10], in which more sensitive electrical control is required for a pinpoint coagulation. In addition, no thermal sensor can be built in the fine tip and monitoring of the tissue temperature during coagulation is not possible. For this reason a temperature controlled coagulation system has more advantages than has a tissue impedance regulated system for laparoscopic surgery, particularly for tubal sterilisation. The tissue temperature was set at 90°C in this study. The purpose of the electrocoagulation is a homogenous coagulation of the tissue. With a conventional electrocoagulation system, in which the tissue temperature cannot be regulated, we often find that the fallopian tube as well as the mesosalpinx beneath the tube are completely burned out. Actually, coagulation of protein begins at about 60°C [5] and a temperature of much higher than 100°C at a coagulation site is not always necessary. Histological and histochemical examinations on rabbit uterine horns in the present study confirm this theory. Coagulation at 90°C was sufficient to induce complete vanishment of LDH activity, and a total occlusion of the lumen was achieved when it was examined 6 weeks later. It has been shown that a temperature of 90°C is sufficient for coagulation in a laparoscopic appendectomy [11]. Experimentally induced endometriosis was also successfully coagulated at 85°C [12]. In addition, sticking of the forceps to the tissue becomes less marked at a temperature below 120°C [13]. This lower setting of temperature has been used also in dermatologic surgery [14]. It should be emphasized that the forceps needs a long cooling time. The forceps reaches up to 300°C in a conventional coagulation system [6]. Once the forceps has such a high temperature, it remains at a dangerous temperature even after the generator is shut off. Laparoscopists pay attention not to touch other organs during coagulation, but very often they pay less atten-
tion after coagulation, while the forceps is still at a high temperature. Low temperature at the coagulation site also reduces this risk.
Acknowledgement Supported by a grant of the German Ministry for Research and Technology (BMFT)
References [1] Population Reports, Voluntary female sterilization: number one and growing. 1990; Series C, Number 10: 1-23. [2] Haney AF. The risks/benefits of laparoscopic cautery for endometriosis. Fertil Steril 1991; 55: 243-245. [3] Levy BS, Sonderstrom RM, Dail DH. Bowel injuries during laparoscopy: gross anatomy and histology. J Reprod Med 1985; 30: 168-172. [4] Gomel V, James C. lntraoperative management of ureteral injury during operative laparoscopy. Fertil Steril 1991: 55: 416-419. [5] Reidenbach HD. Hochfrequenz- und Lasertechnik in der Medizin. Berlin: Springer Vertag, 1983. [6] Semm K. Physical and biological considerations limitating against the use of endoscopically applied high-frequency current in the abdomen. Endoscopy 1983; 15: 282-288. [7] Kastendieck E, Mestwerdt W. Tierexperimentelle und klinische Aspekte der laparoskopischen Tubensterilisation. Geburtsh Frauenheiik 1973; 33: 971-978. [8] Peerse AGE. Histochemistry. Edinburgh: Curchill Livingston, 1972. [9] Moringlane JR, Koch R, Sch/ifer H, Ostertag CB. Experimental radiofrequency (RF) coagulation with computer-based on line monitoring of temperature and power. Acta Neurochir 1989; 96: 126-131. [10] Patil AA, Yamanashi W. Electroconvergent cautery. Neurosurgery 1994; 35: 785-787. [11] Waleezek H, Roeknagel St, Hegelmaier Ch, W61k G. Temperaturentwicklung bei bipolarer Hochfrequenzcoagulation am Appendixstumpf. Chirurgia 1993; 64: 1036-1039. [121 Kato K, Biihler K, Schindler AE. Electrocauterization in rats of experimentally induced endometriosis at a low temperature. Hum Reprod 1995; 10: 2423-2426. [13] Bergdahl B, V,~llfors B. Studies on coagulation and the development of an automatic computerized bipolar coagulation. J Neurosurg 1991; 75: 148-151. [14] Bergdahl B, Stenquist B. An automatic computerized bipolar coagulator for dermatologic surgery. J Dermatol Surg Oncol 1993; 19: 225-227.