POWERED INSTRUMENTS

Electric Instruments

Mono-polar diathermy(cont)


The purpose of the indifferent large surface electrode in mono-polar diathermy, is to provide a surface of sufficient area to avoid any heat effects at this site.

- This is because the indifferent electrode is in contact with hundreds and thousands of more cells than the live electrode which results in a lower density of current in each of these cells.
- If the electrode is applied correctly as described below; little heat is generated in this area.
- The commonest type of indifferent electrode is a flexible metal plate. The thin flexible metal plate electrode can either be placed under the patient’s body (sacrum) or carefully bandaged round the thigh to ensure even contact with the skin.
- It is necessary to use electrode jelly, if the patient is hairy, shaving beforehand is advisable as hair acts as an electrical resistance.
- If the patient’s skin is dry as in our dry climate, moistening with water or saline can be used with advantage before applying the plate. The plate can be wrapped in a moist sheet.
- Replace a plate electrode which becomes uneven, otherwise areas of irregular contact with the skin result, which could allow points of high current density and risk of burns.
- The electrode is connected to the high frequency electrosurgical unit indifferent or earth terminal by a heavy insulated wire.
- Risk of accidents is possible.
Bipolar diathermy is a safer alternative.


With a bipolar system the surgeon’s instrument, usually in the form of a forceps, Combines both electrodes so that current flows down both limbs of the forceps
Only the tissue gripped between the tips of the forceps receives the current.
Eliminating the need for an indifferent electrode.
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