Diathermy Safety — FRCA Primary MCQ

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EasyPhysics & Clinical MeasurementDiathermy SafetyFRCA Primary

During the use of monopolar diathermy, which practice concerning the dispersive return electrode best reduces the risk of a return-site thermal burn?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: A — Apply it with broad, complete contact against suitable intact skin

Explanation lettering: C = shown as A · D = shown as B · A = shown as C · E = shown as D · B = shown as E

C is correct. In monopolar diathermy, current passes from the small active electrode through the patient to a dispersive return electrode. Current density is current divided by contact area; therefore broad, complete plate contact spreads the current and limits local heating. Partial detachment markedly reduces the effective area and can produce a return-site burn. The plate should be applied to intact, dry skin over a vascular, muscular area rather than a bony prominence or scarred or damaged skin. It must not be omitted in monopolar diathermy: omission would leave no intended low-resistance return pathway. A separate patient plate is unnecessary only with conventional bipolar diathermy, where the active and return electrodes are both incorporated into the instrument tips.

Reference: Worcestershire Acute Hospitals NHS Trust. Electro Surgery Theatre Policy, sections 3, 5.2 and 5.7. Approved 2025. https://apps.worcsacute.nhs.uk/KeyDocumentPortal/Home/DownloadFile/2204