Electro-Surgery Helsinki, 23-24 September 2004 Nigel R Hircock Basic electro-surgical circuit – (Monopolar) Active cable/Path Power supply Source - Gen Patient Surgeon Patient Return Electrode Return cable/path High current density at the narrowing of an electrical conductor creates heat 220 Volt 50 Hz Tissue on plate is part of the circuit 220volt/50Hz High current density = heat development in tissue Active Electrode Return Electrode Low current density / No heat development in tissue Why not 50 Hertz Alternating current at frequencies from 1 to 100,000 Hertz will interfere with the neuro-muscular system. Above 100,000 Hertz these stimuli occur too quickly to affect the neuro-muscular system. 50 Hz 100 Khz 550 Khz 1550 Khz 54 – 880 MHz 350 KHz to 3.3 MHz Electrosurgery Neuromuscular Household Stimulation ceases Purposes TV AM Radio FM Radio Below 100 Khz – Electrical shock Above 100 Khz - No electrical shock What it does? Vapourises & De-Hydrates across almost all tissue types Basic electro-surgical circuit - Monopolar Active cable/Path Power supply Surgeon Source - Gen Patient Patient Return Electrode Return cable/path Vaporization & De-Hydration Cut/Vaporization: High current concentration at active electrode causes intense heat in tissue (above 100c) Coagulation (Dessication) Intermittent supply of current to a larger electrode causes less intense heat into tissue (below 100c), allows heat dispersion Energy Coagulation Coagulated cell Dehydration through heating Cut Intense Energy Exploded cell Cell expands through increase in pressure Wave forms pure cut blend cut desiccation fulguration Pure cut uses the lowest level of voltage Monopolar Electrosurgery Cut Coagulation Pure Blend Fulguration Dessication Pure cut Blend Fulguration/non contact coag Dessication 1 Dessication 2 Dessication 3 Spray coagulation Blade electrode or fulguration Principle: Bleeding vessel Current follows Path of least resistance Limiting power settings by limiting contact Blade electrode Micro Needle electrode Choice of electrode & technique determines tissue effect Forceps - tips The electrosurgical effect is influenced by: 1. Contact Time 2. Power Settings of Generator 3. Type of electrode used (Current Density) 4. Whether Cut or Coag activated 5. Tissue Impedance 6. Distance from Active to Return Bipolar electrosurgery in egg white/glass Bipolar Forceps coagulation Saline Correct Incorrect Correct Incorrect Some Issues Usually, a very safe device to use, however, these machines are often seen as the most hazardous device used in an OR! WHY? The patient return electrode General rules for safe practice Minimally Invasive Surgery issues Pad site burns are prevented by assuring optimal conditions at the pad-patient interface. High current concentration/density Low current concentration/density Pad site burns are caused by adverse conditions at the pad-patient interface which result in increased current density. Current density increases when – current removal area is too small – heat is applied for too long – power setting is too high High current concentration/density Plate Burns !!! A burn under the patient plate is ALWAYS negligence RF Current RF Current Monitoring Current Basic rules 1. Position plate as close as possible to surgical site 2. Check contact of plate throughout procedure Avoid the following patient plate locations Scar tissue Metal implants Pacemakers Bony structures Monitoring electrodes Areas of moisture concentration Glove burn (“Bovie-bite”) Result glove burn ! Whoops??? Causes of glove burn Activation of fulgurate or spray output High power settings Surgeons technique Open circuit activation Removal of forceps whilst activating Carbonisation causes higher leakage current due to increased resistance Quality of gloves Recommendation: Use Cut or Dessicate Other Complications • Bowel gas ignition • Staple line/clip conductivity • Current Density Complications • Prep fluid Electrosurgery Safety Considerations for Minimally Invasive Procedures Direct Coupling Active Telescope Electrode with Camera Laparoscope View Bowel Metal Instrument Insulation Failure Abdominal Wall Metal Trocar Electrode Insulation Failure Cannula Electrode Tip Bowel Laparoscopic View Insulation Failure Thermal injury caused by Insulation Failure of electro-surgical instrument during Laparoscopic Cholecystectomy Capacitor Air (Insulator Metal Coil Metal Coil Conductor Conductor Intended Current Induced Flow Current Capacitance Increases with Use of – Longer instruments L – Higher voltages – Narrower diameter cannulas Instrument/Metal Cannula Configuration Creating a Capacitor Abdominal Wall Conductor (Metal Cannula) Conductor (Electrode Tip) Insulator (Electrode Insulation) Laparoscopic View Instrument/Plastic Cannula Configuration Can capacitive coupling occur? Abdominal Wall Conductor Insulator (Plastic Cannula) (Electrode Tip) Insulator (Electrode Insulation) Laparoscopic View Instrument/Hybrid Cannula Configuration Capacitively Coupled Fault Condition Capacitively Coupled Energy to Metal Cannula Plastic Collar Electrode Tip Bowel Energy dispertion Energy Dispertion Hybrid Trocar/Cannula System You make one yourself. Conclusion Electro-Surgical devices can be a potential hazard in an Operating Room. However, they can also be very safe, its always the driver in control!
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