Surgical Diathermy
Surgical diathermy is an equipment that
generates a high- frequency current. The patient is connected to a large
contact electrode. The other electrode is small.
• when
the current is passed through the patient’s body between two electrodes, the
effect is to produce a concentration of current at the smaller electrode in
the hand of the surgeon
• As the
surgeon applies his ‘live’ (small) electrode to the tissues, the current passes
through the touched tissue cells and owing to the tissues electrical
resistance, heat is generated at this small contact point (Fig. 2.3A)
• The
effect is localized because with monopolar system the current from
the‘live’(small) electrode spreads out in the patient’s body and travels to the
‘indifferent’ electrode which is a large electrode placed in contact with the
patient’s body (thigh or sacrum)
• A high
density of current occurs only immediately beneath the live electrode because
further away (except under fault conditions) the current density is too small
to have any heating effect.
The
purpose of the indifferent large surface electrode 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 or even
thousands more cells than the live electrode which results in a correspondingly
lower density of current in each cell
• If the electrode is applied correctly as
described below, negligible heat is generated in this area
• The commonest types 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 wide contact with the skin
• It is unnecessary to use electrode jelly,
though if the patient is hairy, shaving beforehand is advisable—as hair acts as
an electrical resistance
• If the patient’s skin is dry, moistening
with water or saline and can be used with advantage before applying the plate.
• Replace a plate electrode which becomes
buckled 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.
With 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 and thus only through the tissue
gripped between the tips of the forceps, thereby eliminating the need for an
indifferent electrode
Any questions be sent to drmmkapur@gmail.com
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