Harmonic scalpel: vibration, cutting and coagulation

The Harmonic system turns electrical energy into mechanical vibration inside an ultrasonic transducer. The blade vibrates about 55,500 times per second, or 55.5 kHz. Electricity does not pass through the patient.

The blade cuts by an oscillating-saw effect. At the same time, vibration and heat denature proteins. The resulting coagulum seals vessels whose walls have been pressed together. Tissue temperatures are lower than with conventional electrosurgery, but the active blade can still overheat with prolonged use.

Vessel size depends on the device and the test. In Landman's 2003 porcine study, the older Harmonic scalpel did not reliably seal vessels larger than 3 mm. Acute collateral tissue injury extended 0–1 mm. By contrast, the HARMONIC FOCUS+ Long Shears specification includes vessels up to and including 5 mm, based on preclinical testing. These two contexts explain the 3–5 mm memory cue. The exact device and mode determine its vessel limit.

References

Johnston & Tobias, Veterinary Surgery: Small Animal, 2nd ed., Ch. 15; Landman et al., J Urol 2003;169:697–700, doi:10.1097/01.ju.0000045160.87700.32; J&J HARMONIC FOCUS+ Long Shears brochure, 059862-180701.