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

An experimental study was carried out to evaluate heat production by an ult rasonically activated device (USAD) using an animal model. In an anesthetiz ed living pig, the gastroepiploic and mesenteric vessels were coagulated an d cut by an USAD at a power level of 70% (n = 8) or 100% (n = 8). During th e division, the time-discrete temperature change on the surface of the anim al tissue adjacent to the blade was measured by thermography. To compare th e USAD with conventional electrocautery (EC), a full-thickness incision of the gastric wall was performed by each device, and the temperature change w as measured. With the USAD, the temperature increased gradually and remaine d below 150 degrees C during the entire activating time at both power level s. By contrast, with EC at 30 W, the temperature increased rapidly and exce eded 350 degrees C within only a few seconds. The area above 60 degrees C r eached 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 r ather than the USAD. With the USAD, heat production is much slower and more limited than with conventional EC; thus, the USAD causes fewer thermal alt erations in adjacent tissue. USAD should be preferred for tissue coagulatio n and cutting during endscopic surgery.