Surgical Diathermy / Electrosurgery

Diathermy is a form of physical therapy that uses high frequency electrical current to generate heat in order to achieve the desired therapeutic outcome. 

Diathermy can be used to warm the body tissues which is helpful muscle pains and to improve the blood supply. 

But in scope of surgery, it is mainly used to cutting tissues and coagulation 

It is vital for surgeons to have a thorough knowledge about the principles of diathermy and to avoid its’ potential complications.

Nowadays diathermy has evolved to a technique which is used in almost every surgery.
Types Of Diathermy
  • Physical therapy (Used in medicine)
    • Short wave
      • The part to be treated is placed between two condenser plates 
      • Used in….
        • Deep muscles and joints pain (Hip)
        • Pelvic inflammatory diseases
    • Ultrasound
      • High frequency acoustic vibrations warm the muscles and increase the circulation
      • Used to treat deep muscle pains 
    • Microwave
      • Induce hyperthermia which serves as their therapeutic effect
      • Used along with radiotherapy and chemotherapy for the treatment of surface tumors
  • Surgical diathermy / Electrosurgery
    • Monopolar
    • Bipolar

Surgical diathermy / Electrosurgery

It is the application of high frequency alternative electrical current to mainly cut and coagulate tissues during surgery
Electrosurgery uses high frequency alternative electrical current ranging from 300kHz to 3MHz.
It is important to note that unlike 50Hz main current frequency, these high frequency electrical currents do not cause intense muscle and nerve activation.


  • When an electrical current passes through a conductor, some of its’ energy is dissipated as heat
  • Therefore, when high frequency alternative electrical current is applied to tissues, it will create intracellular oscillation of molecules within the cells leading to generation of heat
  • This dissipated heat is used for various therapeutic application 
    • Monopolar diathermy
    • Electricity flows from the active electrode which is held by the surgeon through the patient to the ground electrode / indifferent electrode / return pad which is placed in contact with the patients skin (Under the buttocks or legs)
    • Localized heating effect is produced at the tip of the active electrode
    • Indifferent electrode is a large plate, therefore the heat generate at that end would not have any effect
  • Bipolar diathermy
    • Electricity flows between the two active electrodes 
    • Electricity would not pass through rest of the patient
    • Has a greater accuracy and safety over monopolar diathermy 

  • Cutting
    • When heat applied to tissue is capable of exploding water into steam, it can effectively divide tissues
    • Generated temperature should be above 100°C
    • Uses a continuous waveform with a low voltage
    • Sparks are more focused, hence perform a cleaner separation of tissues 
  • Coagulation
    • Heat results in cell death by dehydration and protein degeneration to seal off blood vessels 
    • Need to generate heat about 60 – 99°C to achieve coagulation 
    • Uses a pulsed waveform with a high voltage
    • Sparks are spread widely 
  • Fulguration
    • Heat should be sufficient enough to coagulate the tissues with carbonization and charring 
    • Need to generate heat at 60°C
  • Sparks causing explosions
    • May ignite any volatile or inflammable gases in the OT
    • Avoid alcohol based preparation to be pooled around the patient
    • In endoscopic diathermy of large bowel – An explosion can lead to colonic rupture
  • Can interfere with pacemakers
    • Major problem with monopolar diathermy
    • Better to use bipolar diathermy in patients with pacemakers 
    • Anaesthetist should carry and appropriate magnet to reset the pacemaker 
  • Capacitance coupling
    • In laparoscopic surgeries, if a diathermy hook is passes though a metallic laparoscopic port is acts as a capacitor and builds up charges by electromagnetic induction
      These charges can pass through the intraperitoneal structures and damage them 
    • Using plastic cuffs significantly increases the risk of capacitance coupling
    • This phenomenon has become rare because of the use of fully plastic ports during laparoscopic surgeries 
  • Current channeling up elsewhere
    • Heat is produced maximally at the tip of the probe
    • If current channel up in a narrow path. it can coagulate the tissues adjacent to the tip
    • Ex : Coagulation of the penis during circumcision or coagulation of spermatic cord during testicular surgery
    • It is best to avoid diathermy in such occasion or use bipolar diathermy 
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