Harmonic Scalpel uses the ultrasound technology, the only form of energy that simultaneously cuts and coagulates the tissue, at the precise point of application, resulting in minimal tissue damage. Because this technique uses ultrasounds, there is less smoke than is generated by both lasers and electrosurgical instruments. The Harmonic Scalpel cuts and coagulates by using lower temperatures than those used by electrosurgery or lasers.

Harmonic Scalpel technology controls bleeding by low temperature coagulation, ranging from 50ºC to 100ºC: vessels are tamponaded and sealed by a protein coagulum. Coagulation occurs by means of protein denaturation when the blade, vibrating at 55,500 Hz, couples with protein, denaturing it to form a coagulum that seals small blood vessels. When the effect is prolonged, secondary heat is produced that seals larger vessels. Because ultrasound is the basis for Harmonic Scalpel technology, no electrical energy is conducted to the patient.

By contrast, electrosurgery coagulates by burning at temperatures higher than 150ºC. Blood and tissue are desiccated and oxidized. The reduced postoperative pain after Harmonic Scalpel hemorrhoidectomy as compared to electrocautery controls, likely results from the avoidance of lateral thermal injury.

The protein coagulum caused by the application of the Harmonic Scalpel is superior at sealing off large bleeding vessels during surgery. Experience has shown that this method is useful in the treatment of large hemorrhoids that may bleed during surgery, thus minimizing blood loss and reducing surgery time.