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ELECTROCAUTERY AND DIATHERMY

Electrosurgery overview

  • Delivered in two ways:

    • Monopolar​

    • Bipolar

  • Alternating current (AC)

    • Mains with frequency at 60 Hz​ can be fatal if even 1mA passes across any human​

    • Modern electrosurgical generators use AC at 200kHz and 3.3Mhz at currents up to 2Amps with no neuromuscular disturbance

  • Heat generated by electrical current is inversely proportional to the surface area through which it flows​

    • Greater energy density is produced with smaller electrosurgical forceps, blade or point​​

Electrosurgery overview

Electrosurgery surgical techniques

  • Four basic surgical techniques

    • Pure cutting​ (yellow switch)

    • Blended cutting (yellow switch)

    • Desiccation (blue switch)

    • Fulguration/spray (blue switch)

  • Pure cutting​

    • Infrequently used due to little haemostasis​

    • Used to minimise lateral heat damage when cutting

    • Best electrode delivers a high energy density

    • Press pedal/switch before contact is made with tissue and approach tissue slowl to deliver small sparks to rapidly boil cellular water of tissue

    • Facilitated by placing tension accross the wound

  • Blended cutting​

    • Used when small vessel haemostasis is required​

    • Electrodes and technique is identical to pure cut

    • Only difference is the attenuated output

  • Desiccation

    • To obtain haemostasis of small blood vessels​

    • Lower energy density instruments are used

    • Heating effect used to dry and denature tissue into coagulum which seals the vessel assested by vessel thrombosis

    • Apply current after grasping vessel or sparks may be produced, causing a cutting effect

    • Char may build up from prolonged overheating, reducing impedance at the instrument tips

    • Power setting should be kept to a level that produces desiccation without carbonation of tissue

  • Fulguration​ and spray

    • Shortest period for each burst of electrical energy in the circuit​

    • Highest voltage and potential for unwanted effects

    • Voltage of circuit is randomly varied with each spark, therefore sparks will be attracted to tissues of different impedance

Electrosurgery surgical techniques

Patient safety

  • Patient plates

    • Used only with monopolar diathermy​

    • Burns do not occur under patient plates during normal usage as size is greater than the surface area at which heating occurs

    • Any action that reduces effective size of patient plate will lead to burns under plate as the energy density increases

    • Modern patient plates are single-use thin metal aluminium sheets covered with adhesive gel that should not be resealed for later use as drying will affect gel conductivity

    • Position plate as close as possible to the operating field over well-vascularised muscular area​ with the long edge of the plate facing the operating site

      • Commonest position is thigh or abdomen

    • To avoid reducing effective size of plate, avoid placing plate:

      • Under compression stockings​

      • Over tattoos

      • Over hair (shave hair before applying plate)

      • Over skin near metal prostheses

    • If plate is compromised, generators will alarm​ and turn off the main electrosurgical current

  • Metal prostheses and jewellery

    • May become an internal unwanted current path if it lies between the operating site and plate during monopolar electrosurgery​ due to lower impedance

    • Potential for tissue damage at the narrower end of the prosthesis

  • Cardiac devices

    • Monopolar current passing along pacemaker may discharge against the endocardium and change the tissue resistance to the low voltage pacing current resulting in inadequate pacing​

    • Best practice to place pacemaker in its basic mode of demand pacing prior to surgery requiring electrosurgery

    • Pacemaker should not come between the operating site and the pad electrode and all cables should be routed away from the pacemaker

    • Cardiac implantable defibrillators may detect electrical noise from electrosurgery and deliver shock to cardiovert the patient, therefore it should eb turned off prior to surgery and turned on again after surgery

  • Ignition hazards​

    • Care should be taken with all flammable substances and allowed to evaporate fully before draping​

  • Smoke hazards

    • Diathermy smoke is noxious and carcinogenic​

    • Where possible, use smoke evacuation through suction to protect patient and staff

Patient safety
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