Electrosurgery and Energy Devices in Gynaecology
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Direct answer
Electrosurgery uses high-frequency electrical current to cut and coagulate tissue, and monopolar and bipolar diathermy are its two main forms in gynaecology. Monopolar current flows through the patient to a dispersive pad, so it can cause stray burns, whereas bipolar current stays between the forceps tips and is safer near bowel and ureter. Vessel sealing devices seal vessels with pressure and bipolar energy, with limited lateral spread.
What you must remember
- Monopolar: current passes from an active electrode through the body to a dispersive return pad, cutting and coagulating, with greater lateral thermal spread and burn risk.
- Bipolar: current passes only between the two tips of the forceps, so only the grasped tissue is heated and no return pad is needed.
- Vessel sealing: pressure and bipolar energy denature collagen and elastin to seal vessels, commonly quoted up to about 7 mm in diameter.
- Ultrasonic scalpel: cuts and coagulates by mechanical vibration rather than electrical current, so no return pad circuit is used.
- Return pad: a large electrode placed on well-perfused muscle with full skin contact and away from metal, so that current disperses safely.
- Capacitive coupling: current induced into an insulated instrument shaft or trocar can burn bowel or skin away from the visible active tip.
- Pacemakers: diathermy can interfere with implanted cardiac devices, so the anaesthetic team's cardiac precautions are followed before use.
Choosing a device and setting the energy
Energy device choice starts with the target tissue and the structures beside it, not with the instrument already on the trolley. The steps below follow the order a surgeon works through before switching the current on.
- Identify the target: Decide whether the need is to cut, coagulate or seal a named vessel or tissue plane.
- Assess proximity: Check how close bowel, ureter and bladder lie, since their proximity sets the risk of thermal injury.
- Choose bipolar near critical structures: Use bipolar forceps where the current must stay within the grasped tissue.
- Set the energy: Use the lowest effective power in short bursts, because high power increases lateral spread.
- Protect the circuit: Place the return pad correctly for monopolar use and keep the insulation intact, checking for stray contact with metal.
- Check before closure: Inspect for burns, bleeding and bowel injury, and record the device and settings used.
Where the exam tries to catch you
Vignettes often ask which device is safe near a critical structure, or why a burn appears away from the site.
- Trap: Assuming bipolar is always safe because no return pad is used. Correct: Bipolar confines the current, but damaged insulation or contact with other metal can still cause injury.
- Trap: Looking for a burn only at the active tip. Correct: Capacitive coupling and lateral spread can burn bowel or skin far from the visible site, often noticed only later.
- Trap: Using vessel sealing for a large vessel because it is energy-based. Correct: Sealing is limited to vessels of modest size, so larger vessels still need ligature.
Frequently asked questions
What is the difference between monopolar and bipolar diathermy in gynaecology?
Monopolar diathermy passes current through the patient to a dispersive return pad and cuts and coagulates larger areas. Bipolar diathermy confines current between two forceps tips, so it is preferred near bowel and ureter and for procedures such as laparoscopic tubal coagulation.
Why does a monopolar diathermy burn appear away from the operative site?
Monopolar diathermy burns away from the operative site occur through stray current, capacitive coupling or poor return-pad contact. The current finds an alternative path through a trocar, an insulated instrument shaft or a metal contact, and burns the tissue at that point.
Where should the dispersive return pad be placed in monopolar surgery?
The dispersive return pad should be placed on a large, well-perfused muscle mass with full skin contact, away from implants and metal. This spreads the current over a wide area so that no single site is heated enough to burn.
Which energy device seals small vessels without electrical current?
An ultrasonic scalpel cuts and coagulates tissue through mechanical vibration rather than electrical current, so it needs no return pad. It is useful for small vessels in many procedures, but it does not replace ligature of large vessels.