V. Hausmann

5.1 General aspects - 42

5.1.1 How it works/Definition - 42

5.1.3 Coagulation - 44

5.1.4 Influences on the surgical effect - 45

5.2 Neutral electrode - 46

5.2.2 Safety systems - 46

5.2.3 The neutral electrode - which, where, how? - 46

5.2.4 Burns under the neutral electrode? - 47

5.3 Rules for safe use - 48

5.3.2 Use of high-frequency surgery in minimally invasive surgery - 48

5.3.3 Other information - 49

Glossary - 50

References - 54

5.1 General aspects

5.1.1 How it works/Definition

What is electrosurgery?

High-frequency surgery or electrosurgery today is an established feature in every operation. Its advantages compared to other techniques are as follows: 4 Tissue dissection possibly with simultaneous haemostatic effect (stops bleeding). 4 Combinations with other techniques, e.g. argon gas surgery or ultrasonic dissection (e.g. CUSA) result in further simplification in surgery.

In addition, electrosurgery is used in both open surgery and also in minimal invasive surgery (MIS).

The user's know-how about handling high-frequency surgical devices is based on what he has been told and also on his own experience. But training literature contains little information about how high-frequency surgery works and its risks.

Basic idea: heat

The basic idea behind electrosurgery is to generate heat. This principle was already known in the past. It was known that glowing metal or hot stones would have a haemostatic or coagulating effect on a wound. Later, technological developments provided other sources of energy, namely electricity (O Fig. 5.1).


One simple means of generating heat by electricity is to reduce the diameter of an electrical conductor to increase

Fig. 5.1. Instruments from the past

Fig. 5.2. The cauterisation technique

the electrical resistance. Heat is produced at the point of reduced diameter by the greater current density (O Fig. 5.2).

Using normal mains power (230 V, 50 Hz), a corresponding transformer could be used to make a generator which lets a thin wire glow red hot for use for local haemostasis. This technique is called cauterisation. But the drawback is that more tissue is damaged by radiant heat than is actually wanted. In addition, this technique cannot be used for cutting.

Cautering or cauterisation are frequently incorrectly confused with high-frequency surgery.

High-frequency surgery

Another possibility is to consider the tissue as resistance between two electrical conductors. In order to generate a surgical effect at the specific site, a small contact surface is required (active electrode), generating a very high current density at the metal/tissue interface. This causes the required heat in the corresponding tissue.

A far larger, conductive area is provided on the other side of the tissue (neutral electrode) which ensures that the current leaves the tissue with a very low density without developing any heat (O Fig. 5.3).



Low current density = no heat generated

Fig. 5.3. High and low current density

Low current density = no heat generated

Fig. 5.1. Instruments from the past

Fig. 5.3. High and low current density

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