Bartholomus Bhm Jeffrey W Milsom and Kiyokazu Nakajima

In laparoscopic surgery, abdominal tissues are dissected using a combination of cutting and coagulation, often with specialized electrosurgi-cal instruments or ultrasonic devices. Precise dissection with minimal bleeding is especially important in laparoscopic surgery. Even minor oozing compromises the laparoscopic view and clearing blood from the field of vision with suction and irrigation may be tedious. Therefore, dissection must be performed with tools that optimize precise tissue cutting and coagulation.

Although many different coagulation and dissection devices are available, they all divide and coagulate tissue by converting various types of energy into heat. Therefore, the effect on tissue is thermal and depends on exposure time and the amount of energy applied to the tissue. Before embarking on a specific discussion of each instrument used to cut or coagulate tissue, reviewing some basic concepts about thermal alteration of tissue is worthwhile.

Tissue reaction to thermal injury depends primarily on the temperature used (Figure 3.1). An increase in tissue temperature up to 60°C results in almost indiscernible changes to the naked eye. Coagulation begins at temperatures above 60°C; it is characterized by shrinkage and blanching caused by the denaturation of proteins, particularly colla-gen.1,2 When the tissue temperature reaches 100°C, the cell water boils, water is converted to steam, and the cell wall ruptures. When the water has evaporated and heat is still applied, the tissue temperature increases rapidly until it reaches 200°-300°C. At this point, the tissue carbonizes and begins to vaporize and smoke. At temperatures more than 500°C, tissue burns and evaporates.1-3

The effect of heat on tissue depends not only on the absolute amount of heat applied to tissue but also on the exposure time to heat. If heat is applied over a very short time (less than 1-2 seconds), the effect is localized because the heat is not conducted to surrounding tissues; even when the heat is great enough to vaporize the tissue, the vaporization is localized. If, however, the same amount of heat is applied for a longer period (greater than 2 seconds), the heat is conducted to the

Figure 3.1. Visible and histologic alterations of tissues as related to tissue temperature.

Figure 3.1. Visible and histologic alterations of tissues as related to tissue temperature.

surrounding tissue, thus increasing thermal necrosis and broadening the vaporization area.

Cutting quality and coagulation quality are inversely related, regardless of the dissection device used (Figure 3.2). Good cutting quality depends on rapid local vaporization of tissue with minimal lateral heat damage. No coagulation will occur because the lateral heat damage is not wide enough to seal the blood vessels. In contrast, the quality of coagulation depends on the width of lateral heat damage: the wider the lateral heat damage, the better the hemostasis. Because as cutting quality improves, the coagulation quality worsens, simultaneously combining excellent cutting qualities with excellent hemostasis is impossible.

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