Ultrasonically-activated devices for endoscopic surgery

Summary

In an ultrasonically-activated device (USAD), the controlled electric current is transformed into mechanical vibration in the transducer. The amplitude of this vibration is amplified in a conical metal horn, attached to the end of the transducer. The shaft of the USAD houses an extension rod, which transmits the amplified vibration to the end effecter. The end effecter in the scissor-type USAD is termed the ‘active blade’. The target tissue is clamped between the active blade and an opposed tissue pad, and effective coagulation occurs. In the USAD technique, frictional heat generated is mostly lower than boiling point, which allows collagens to denature with water and form a glue-like material to seal the vessel. Division of the tissue is caused mainly by ‘mechanical wear’ from the vibrating blade. Cavitation occurs at the tip of the active blade. As cavitation can be traumatic and fragment the tissue, any contact of the tip of the active blade with important tissue should be avoided. Recent reports on the USAD's ability to achieve haemostasis are excellent, suggesting that the cut-ends of the vessels withstand the high intraluminal pressure. However, the following four factors are considered pitfalls: the vessel could be divided before it is sufficiently occluded, due to excessive tension; the active blade could cross the vessel incompletely; adjacent vessels could be injured with the reverse side or the tip of the active blade.

Key Words:

• ultrasonically-activated device
• ultrasonic dissection
• endoscopic surgery
• vessel coagulation
• vessel division