Experimental justification of laser parameters for preventive laser (970 nm) vessel coagulation in intraoperative bleeding

Intraoperative bleeding impairs visualization of the surgical field. Working in a practically bloodless operating field reduces the duration of surgery and reduces the need for cautery use, which reduces pain in the postoperative period and the risk of delayed bleeding after tonsillectomy.

Objective – to select the parameters of a diode laser with a wavelength of 970 nm in order to get optimal hemostatic effect and to develop a technique for safe preventive coagulation of vessels in the surgical wound using diode laser with a wavelength of 970 nm for their bloodless section.

Materials and methods. 47 Wistar rats weighing 300–400 g were used in the experiment. After preparation of the surgical field, three groups of vessels were isolated from each rat. The rat vascular bed was used as a model of tonsillar vascular bed in the patients undergoing tonsillectomy. All animals were divided into groups, depending on the laser power. For the experiment we used a diode surgical laser with a wavelength of 970 nm in a constant mode, a fiber diameter of 400 microns. After coagulation of each vessel, a visual and microscopic assessment of the vessels was performed. The study of the possibility of vascular coagulation was evaluated after the vessel was cross-sectioned with a scalpel.

Results. Damage to the walls of blood vessels was not observed at powers from 5.0 W to 7.0 W. At the same time, at the laser power from 5.0 W to 6.0 W there was no hemostasis after crossing the vessels. At a power of 6.5 W, adequate hemostasis was observed only in 42 % of cases. The coagulation mode of a diode laser with a wavelength of 970 nm, which is the most effective and safe for surrounding tissues, was observed at a power of 7.0 W

Conclusions. Exceeding the power levels of a diode laser with a wavelength of 970 nm leads to the formation of carbonization of the surrounding tissues, to a damage of the vascular wall. In order to prevent bleeding, arteries with a diameter of more than 1.5 mm must be stitched. Small vessels with a diameter of less than 0.4 mm do not require preventive coagulation and can be coagulated during the incision with a laser fiber.

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