MRCS Surgical Diathermy

MRCS Surgical Diathermy
Definition:
Diathermy involves the use of high frequency alternating electrical current (A.C.
400kHz-10MHz) to produce a localised heating effect which in turn causes local tissue
destruction. It can be employed to cauterize, cut, desiccate and fulgurate (destroy) tissue.
It is also known as electrosurgery/electrocautery/electrocoagulation.
Note:
1. Greek root - ‘Dia’ - through and ‘thermy’ - heat.
2. Low frequency may stimulate neuromuscular tissue.
Types:
Monopolar
• Current flows from generator to instrument then through patient to a second electrode
(indifferent return electrode) - the diathermy plate.
• Due to surface area of instrument being much smaller than plate there is localised heat
produced at tip of instrument and relatively minimal heat at the plate.
• Surface area of plate over 70cm3.
• Higher power/wattage required.
Bipolar
• Within the instrument two electrodes are combined e.g. forceps.
• When the two forceps tips or electrodes are in contact the circuit is completed -
creating localised heat.
• No patient plate electrode required.
• Lower power/wattage required.
• Safer in patients with pacemakers.
Modes:
The effect of diathermy relies on the current and wave-form.
Cutting
• Continuous current with a sinus wave-form allowing cutting and parallel cauterizing of
the tissue edges.
Coagulation
• Interrupted pulses of current with a square wave-form - mainly for cauterizing and
fulguration.
Blend
• A mixture of both cutting and coagulation modes.

MRCS Surgical Diathermy
Complications:
Complication Cause
Burns • Superficial burns from pooling of flammable liquid - spirit based
skin preperations.
• Erroneously placed patient plate electrode.
• Retained heat in electrode.
• Poorly insulated diathermy lead.
• Inadvertent use.
Explosion • Ignition of volatile anaesthetic agents e.g. anaesthetic gases in
bowel.
Electrocution • Poorly insulated diathermy leads.
Pacemaker
interference
• Can reprogram pacemaker.
• Pacemaker wires may conduct current to the heart causing
myocardial burns.
• Prevent - preferentially use bipolar. Only use monopolar in
short, low power waves and ensure plate is positioned so that
current travels away from pacemaker.
Channelling • Avoid use of diathermy on appendages/ narrow pedicles.
Coupling • Current can be induced in other insulated metal conductors -
e.g. metal laparoscopic ports.
Safety:
• Ensure appropriate training.
• Equipment maintenance.
• Avoid incorrect placement of plates - ensuring good contact on dry skin and at least
70cm3 surface area.
• Wipe excess spirit based liquids.
• Sound when diathermy on.
• Place in insulated quiver when not in use.
• Ensure patient is not in contact with earthed materials.