Lateral thermal damage to rat abdominal wall after harmonic scalpel application.

Background: Use of the Harmonic Scalpel transduces a lower amount of energy to tissues, thereby limiting the potential for lateral thermal damage and deep penetration because only low temperatures are reached. The working principle of the Harmonic Scalpel is the transformation of electric power into the longitudinal mechanical movement of the instrument tip. This study aimed to determine the effects from varying durations of Harmonic Scalpel application on the experimental model of rat abdominal wall without skin.

Methods: After the rats had been anesthetized, and a laparotomy was performed. The Harmonic Scalpel shears were used on the muscular part of the abdominal wall without skin. Different durations of output power 3 were applied: a single 5-s application, a single 10-s application, and a regimen of two sequential 5-s applications. Each animal in each group of 10 received five individual activations, after which the animals were killed. Tissue samples were fixed and embedded in paraffin before sections were taken and stained. Using light microscopy and morphometric imaging analysis, the width of tissue lateral thermal damage was measured from the point of Harmonic Scalpel incision.

Results: The rat abdominal wall showed lateral thermal damage over a mean width of 0.0522 +/- 0.0097 mm after a 5-s Harmonic Scalpel application, a damage width of 0.1544 +/- 0.0419 mm after a 10-s application, and a damage width of 0.1020 +/- 0.0430 mm after a 5-s application followed by 5 s of inactivity and another 5 s of activity. These differences in thermal damage width between all the groups are statistically significant.

Conclusions: The findings lead to the conclusion that tissue lateral thermal damage after Harmonic Scalpel application at standard output power is greater when a longer sustained period of application is used. Lateral thermal damage also is greater if the Harmonic Scalpel application time is continuous rather than of the same total duration with a brief midpoint interruption.