1. Different classification

A plasma knife is a surgical tool that uses a small jet of high temperature against the surface of tissue to simultaneously cut and cauterize tissue, in some cases sealing blood vessels up to 3mm in diameter. For example, transecting a large lobe of a dog's liver with a plasma knife can result in minimal blood loss without the need to ligate or block the blood flow into the liver.

High-frequency electrosurgical knife (high-frequency surgical instrument) is an electrosurgical instrument that replaces mechanical scalpels for tissue cutting. It heats the tissue through the high-frequency high-voltage current generated by the effective electrode tip when it is in contact with the body, so as to realize the separation and coagulation of the body tissue, so as to achieve the purpose of cutting and hemostasis.

2. Different cutting principles

There is a DC arc in the tip of the plasma knife. When the working gas (argon or helium, or a mixture of the two gases) passes through the arc, the electric energy is converted into thermal energy, ionizing the gas and increasing the temperature. The neutral electric high-temperature plasma gas emitted from the tip of the knife is a visible jet with a diameter of less than 1 mm, a length of about 1 cm, and a temperature of 3000C.

When the high-frequency high-voltage current generated by the high-frequency electrosurgical knife passes through the high-impedance tissue, it will generate heat in the tissue, causing the tissue to vaporize or coagulate. During electrosurgical use, the resistance varies from 100 ohms to 2000 ohms. As the tissue coagulates, the water in the cells vaporizes, drying out the tissue, causing a constant increase in electrical resistance, and eventually a complete cessation of current flow.

3. Different functions

Plasma knives work similarly to carbon dioxide laser knives, cutting and cauterizing tissue. Lasers use electromagnetic energy in the infrared wavelength range, while plasma knives use high-temperature jets. Electrosurgical knives are another type of hot knives that were used clinically as early as the early twentieth century, where electrical energy is applied to tissue.

Because high-frequency electrosurgery can perform cutting and coagulation at the same time, it is widely used in operations that are difficult to access and perform with mechanical scalpels (e.g., abdominal duct ligation, prostate urethral tumor resection).