Article 4 - Complications of laparoscopic surgery - Thermal injury
There are different mechanisms by which ‘burns’, i.e. thermal injury to body structures can occur, with an estimated quarter of all injuries being due to the effect of the heat generated by the diathermy instruments used to control bleeding.
Electric current is used to generate heat which, when applied to tissues that are bleeding, can coagulate the blood and adjacent bleeding tissues, and sealing the disrupted blood vessels (this process is known as diathermy). The current usually passes from the area that is being sealed (i.e. at the end of the instrument used) back to the ‘return plate’. Most often the current is dissipated on its arrival to the return plate (a broad area of material that provides earthing of current in a safe manner, dissipating the energy). However, if the current passes across different structures that are close together or adherent, then as a small surface area is involved, the current may be sufficiently powerful enough to cause a burn at that point
The use of pulsed energy helps the avoidance of build up energy at such high-risk sites. The duration of the application of the electric current and current strength also affects the likelihood of a thermal injury.
Methods of injury
A. Direct application
C. Stray current
D. Capacitive coupling
Thermal injury occurs owing to the direct application of diathermy to tissues. Factors implicated in these injuries include the hand co-ordination and visual-spatial co-ordination of the surgeon, mistaken identification of a tissue/mistaken contact with tissue or close proximity to tissues and the duration and amount of current used, the longer and the stronger the application of energy, the greater the amount of damage. Adjacent spread can be reduced by keeping the forceps blades apposed.
When the activated electrode is close to another metal instrument or device, then the current may be diverted along the course of that other instrument or device, with injury occurring at contact sites. Looking at the electrode when it is in use and not making contact with other instruments or devices are key in avoiding such a thermal injury.
This is due to the leakage of current from the diathermy apparatus. This may be from the shaft, which may be due to faulty/insufficient insulation as seen after frequent re-sterilization of the equipment.
This is seen when a current pass from the active electrode into adjacent structures which may occur when high prolonged voltage use is seen. This is more likely to happen in longer diathermy tools, and where there is less in the way of insulating materials on the diathermy device. These are important factors to note in operative complications.
Return site burns
The return plate (also called the dispersive pad) provides the pathway of lowest resistance for flow of electric current; however, if it is improperly attached, or there is an excessive amount of current, then the current may, in part, be diverted e.g. to other earthed points of contact such as the ECG leads, or intravenous stand or other conducting materials, so causing a thermal injury.
The next article in this series outlines the clinical manifestations of complications seen post laparoscopic surgery.