Experimental study on heat production by a 23.5-kHz ultrasonically activated device for endoscopic surgery

Abstract.

An experimental study was carried out to evaluate heat production by an ultrasonically activated device (USAD) using an animal model. In an anesthetized living pig, the gastroepiploic and mesenteric vessels were coagulated and cut by an USAD at a power level of 70% (n= 8) or 100% (n= 8). During the division, the time-discrete temperature change on the surface of the animal tissue adjacent to the blade was measured by thermography. To compare the USAD with conventional electrocautery (EC), a full-thickness incision of the gastric wall was performed by each device, and the temperature change was measured. With the USAD, the temperature increased gradually and remained below 150°C during the entire activating time at both power levels. By contrast, with EC at 30 W, the temperature increased rapidly and exceeded 350°C within only a few seconds. The area above 60°C reached a final width of 10 mm for the USAD, as compared with 22 mm for EC. Microscopically, thermal alterations such as carbonization and vaporization were much more severe and extensive in the adjacent tissue when using EC rather than the USAD. With the USAD, heat production is much slower and more limited than with conventional EC; thus, the USAD causes fewer thermal alterations in adjacent tissue. USAD should be preferred for tissue coagulation and cutting during endscopic surgery.