To the Editor:

With regard to the article by Soderstrom and Levy entitled "Bipolar systems--do they perform?" (OBSTET GYNECOL 69.425, 1987), the authors make the following statements which need to be reviewed:

1. "Because the electrical energy available in a bipolar system is restricted by its design, complete coagulation of the fallopian tube cannot be determined by a visual endpoint." Most bipolar generators available today produce 50 watts of power, although only approximately 20 watts are needed to totally seal the fallopian tube. The problem is not the amount of energy available, but the waveform of the current being used, that is, the peak to peak voltage. The problem with visual inspection, as pointed out by Hausner' during bipolar surgery for female sterilization, is the realization or judgment of the surgeon evaluating the degree of blanching. The visually observed blanching, left and right of the jaws of the forceps, should extend at least 2-3 mm. Both ELMED and the Richard Wolf Company use a meter to objectively measure the existence of current flow. Such meters can also be deceived by capacitive current discharge between the conductors of the bipolar forceps or the RF-cables, particularly at higher frequencies. In a study by Hausner,² we measured the capacitance and impedances of various bipolar forceps and RF-cables, and found an enormous difference at a frequency above 1 MHz. For example, the Kleppinger forceps with its standard 8-foot RF-cable measured 86 pF, the Martin forceps with an ELMED RF-cable measured 38 pF, and the same Martin forceps with an original Martin cable measured 726 pF. A 3-mm 0 Eder forceps with an ELMED RF-cable measured 132 pf. It is obvious that the RF-cable used is as important as the type of bipolar forceps used. We consider the standard Martin RF-cable unacceptable for use in laparoscopic sterilization. The jaw configuration of the forceps is also of great importance. The pressure used during current application is significant with respect to success or failure in sealing the fallopian tube. The Kleppinger forceps and some others depend on the pressure applied by the surgeon, while the Martin and some of the ELMED forceps are spring-loaded, providing constant pressure during the coagulation process. The springloaded forceps perform in a more reliable and consistent fashion, particularly when energized by systems that do not include any type of coagulation monitor. The above study clearly shows that.

2. "Most electrogenerators do not increase the current output as the resistance increases. The Wolf bipolar generator, which was designed in conjunction with the Kleppinger forceps, compensates as tissue impedance develops." This is an untrue statement. The Wolf bipolar unit used in this study does not incorporate the output compensation system described. Such a system was introduced by ELMED in 1973, with the ELEKTROTOM 120 models. Wolf should retract its claim. When we introduced the bipolar sterilization approach, which offered many advantages over the unipolar method, we warned that the observation criteria must be altered. Unipolar current burns the fallopian tube at a high temperature in a relatively short time, while a proper bipolar coagulation may require between 30-60 seconds. Many surgeons do not have the patience to apply current for such a long time; thus, the result is recannulization of the fallopian tube and pregnancy. It is too bad that investigators did not use the Wolf bipolar unit with non-Wolf forceps. In the article they state that "because of its design, the Wolf bipolar generator will not adapt to the other bipolar forceps." On what is this statement based? If the Wolf bipolar unit measures current flow, why should it not work with competitive forceps?

3. The Cameron-Miller, Storz, and Valleylab generators provide a modulated current for bipolar application, not recommended because of the relatively high voltage and surface coagulation temperature and effect. Dr. Hulka recommended a musical current flow indicator in and above the visual indicator, because the endoscopist can more easily coordinate the current flow pattern by sound. ELMED developed such an audible/visual indicator, based on this recommendation.

Karl Hausner, President ELMED, Inc. 60 West Fay Avenue Addison, IL 60101

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