Electrocautery 101 New York Society of Gastrointestinal Endoscopy 31 st Annual Summer Fellows Course

Transcription

1 Electrocautery 101 New York Society of Gastrointestinal Endoscopy 31 st Annual Summer Fellows Course Renee Williams, MD Assistant Professor of Medicine NYU School of Medicine Division of Gastroenterology July 14 th 2018

2 Objectives 1. Discuss the basics of electricity 2. Discuss the principles of electrosurgery in endoscopy 3. Differentiate monopolar and bipolar modes 4. Describe safety measures for procedures that incorporate electrosurgery

3 Electricity Electrosurgery Christian Erbe Tübingen, Germany 1923 William Bovie & Harvey Cushing Boston, USA 1926

4 Electrosurgical Generators 2019

5 BASICS OF ELECTRICITY

6 Electricity Current is the flow of electrons over time (Amps) Resistance and impedance represent an impediment to the flow of the electrons (Ohms) Voltage is the power required to push the electrons through that resistance (Volts) Electrosurgical generators turn alternating current into thermal energy within tissue

7 Ohm s Law Voltage= Current X Resistance As resistance increases, such as when tissue dessicates, more voltage is needed to maintain flow Voltage also increases the risk of thermal injury to the tissue With some generators, when a predefined voltage or resistance is reached, the current will stop Reduces the risk of injury

8 Basic Principles of Electricity 1. Always seeks the ground 2. Always seeks the path of least resistance 3. Must complete a circuit.

9 PRINCIPLES OF ELECTRICITY IN ELECTROSURGERY

10 Resistance = Impedance C O N D U C T O R S GI Mucosa Skin Bone Blood Muscle Fat Plastic I N S U L A T O R S

11 We All Differ Electrically Age, disease processes, body habitus, hydration Generators have to cope with this

12 Electrosurgical Devices Won t Electrocute You Due to Frequency Low 60Hz High 350,000-3,000,000H z

13 At High Frequencies, the Risk of Adverse Events is Almost Eliminated MHz TV 60 Hz 100 khz 350kHz- 100,000 Hz 3MHz Household Neuromuscular stimulation and myocardial sensitivity ESU s Thermal transfer with almost No risk khz AM Radio

14 Cut vs. Coagulation Differ in rate and magnitude Coagulation induces a slower rise in tissue temperature (70-100deg C) Cells dehydrate and shrink. Dessication Cut currents cause a more rapid and higher temperature (>100deg C) Water in cells boil and cells burst Cleaves the tissue in contact with the electrode

15 Thermal Effect on Cells Temp Tissue Effect 40 ο C Reversible cellular trauma 50 ο C Irreversible cellular trauma 70 ο C Coagulation >100 ο C Cutting 200 ο C Carbonization fulgaration

16 Blended Current Coagulation adds pauses to the current, allowing the tissue to cool, with greater coagulation

17 Potential Safety Differences Depth of tissue injury is greater with coagulation vs. blended and pure cut No significant difference in total adverse events based on retrospective analyses Possible increased the risk of immediate and early bleeding (blended and cut) Possible increased the risk of delayed bleeding (coagulation)

18 MONOPOLAR AND BIPOLAR CIRCUITS

19 Completing the Circuit: Monopolar Cautery

20 Monopolar Electrocautery Current is conducted by the body so a grounding pad is necessary Monopolar cautery polypectomy sphincterotomy needle-knife APC

21 Completing the Circuit: Bipolar Cautery

22 Bipolar Electrocautery Bipolar cautery Hemostasis Tumor ablation Electrohydraulic lithotripsy Barrett s RFA ablation The circuit is completed between 2 points on the active electrode so grounding pad is not needed

23 SAFETY MEASURES IN ELECTROSURGERY

24 Potential Complications Burns at the neutral electrode pad site Fetal stimulation Capacitive coupling discharges (burns) Interaction with implanted cardiac and noncardiac devices Neuromuscular stimulation Bowel explosion

25 Neutral Pad Burns When monopolar current is used, the large surface area of the return electrode should disperse the current density, preventing burns Most units can detect poor pad contact quality and shut off the current Burns are very rare

26 Rules of Pad Placement Area should be clean and dry Good musculature/vascularity Avoid bony prominences, scars, hair, foreign bodies, and artificial joints Close to electrosurgical site Don t place structures that can be harmed between active and neutral electrodes (gravid uterus, devices) Do not place over metal objects

27 Avoid Tenting

28 Return Electrode DON T CUT!

29 Neutral Pad Site Burns

30 Pad Placement > Well vascularized area > Shortest circuit possible > Optimum on flank > Alternatives thigh or arm

31 Leakage From Cables by Capacitive Coupling Transfer of a portion of the current from the active electrode to a second electrically conductive structure through the insulation Discharge is delivered to an undesired location (patient or endoscopist)

32 Modern Pacemakers & ICDs > Should not be affected by unit current > Do not place devices between the active and neutral electrode. > Use of current may damage older pacemakers. Use bipolar current when possible since the circuit will be kept away from the device

33 Neuromuscular Stimulation Should Not Occur With High Frequency Current > Loose wires > Broken wire bundles > Defective/broken adapters

34 Colonic Explosions > Poor bowel preps may cause bowel explosions when combined with any electrosurgery > The risk is from trapped hydrogen and methane > Colonic explosions reported > Gastric explosion reported

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37 THANK YOU