1. What is a Watt? Everything you ever wanted to know about Electrosurgery.
Fahad bamehriz, MD

2. History Beer 1910: First endoscopic use of electrosurgery
Benjamin Franklin: 18th Century-first experiments
Arsene D'Arsonval: first to experiment with alternating currents in the late 19th century
first to study clinical effects with modulated and non-modulated current
Beer 1910: First endoscopic use of electrosurgery
Fulguration of bladder tumours using the cystoscope
Bovie and Cushing 1928: first electrosurgical generator with continuous sinewave current

3. Fundamentals of Electricity
Electricity is electrons freed from atoms
Current <I> is electrons flowing in the same direction (measured in amperes)
flow from negative to positive terminal
Voltage <V> is the electromotive force to drive the current through the conductor
difference in potential between the poles
Current that is one-way is direct current <DC>

4. Fundamentals of Electricity
Current that reverses direction is alternating <AC>
The movement of electrons reverses direction at regular intervals <cycles per second=hertz>
Resistance <R> is the difficulty that a material presents to the flow of electricity <ohms>
WATER IS THE KEY FOR TISSUES
More water less resistance

5. Fundamentals of Electricity
High School Physics:
Ohm’s Law: V=I X R
Power is the rate of doing work <watts>
W=I X V W=I2 X R W=V2/R
Total quantity of electrons moved and the pressure gradient against which the movement occurred

6. Alternating Current Household power: 60 cycles/s
AM Radio: kHz
Electrosurgical generators: kHz

7. Current Waveforms Modulated current is just interrupted current
this is the COAG button
highest peak to peak voltage
Non-modulated current is a continuous sinewave
this is the CUT button
low peak to peak voltage

8. Current Waveforms

9. Cellular Effects Vaporization (cutting): Dessication/Coagulation:
rapid oscillation of cell positive and negative ions causing high temperatures (600 °c) and converting mechanical energy to thermal energy.
Cell expansion and steam formation lead to cell explosion
Dessication/Coagulation:
slower process with temperatures at °c and evaporation of intracellular water and protein denaturation

10. Cellular Effects

11. Cellular Effects
Fulguration: Superficial coagulation of broad tissue surface using electrical arcs of high voltage of modulated current
rapid desiccation and tissue resistance limits current flow
the only really good reason to use modulated current

12. Cellular Effects
Cautery: destruction of tissue by the application of heat or a caustic substance
ie: grasping tissue with pickups and touching pickups with active electrode

13. Capacitance Property of an electrical circuit to store energy
Capacitor=any device that can create capacitance
exists when two conductors with different potentials are separated by an insulator
the difference between them creates an electrostatic force
capacitance is directly proportional to voltage

14. OR Capacitors Surgeons Pts’ jewelry OR table IV pole idle electrode
surgical instruments
induced currents may lead to alternate current pathways back to ground
surface area key…small is bad

15. Grounding A form of conductive connection between a circuit and earth
earth can absorb infinite electrical charges
equalization occurs
Risk of alternate site burns (EKG electrode) eliminated by dispersive return electrode (blue pad)
low impedance route back home
remember hair, scar and fat free

16. Dispersive (return) Electrode Injury

17. Return Electrode Modern generators have alarms
place in a non-dependent area
area with good blood flow (water concept)
*****if the generator doesn’t work: check return electrode**********
DO NOT TURN UP THE GENERATOR!!!

18. Direct Coupling
Activated electrode unintentionally touches another metal object
may be out of the field of view
may be undetected
avoided by staying aware of location of all instruments

19. Direct Coupling

20. Capacitive Coupling
Induction of stray current to surrounding capacitor through insulation of active electrode
active monopolar electrode, insulation, metal cannula
worse with higher voltage, smaller cannulas, longer electrodes
Minimize by using a Non-modulated (cutting) current
Avoid hybrid (metal and plastic cannulas)

21. Capacitative Coupling

22. Insulation Failure Insulation can be damaged by very high currents
Breaks and holes can be caused by cannula valves or cleaning
If defective spot on active electrode touches tissue, damage may occur
inspect instruments for damage

23. Current Density Electrons congregate on edges
determined by shape and size of electrode
same device may be multifunctional
i.e. flat vs. sharp edge of spatula electrode
important for loop excisions, hysteroscopy and of course laparoscopy

24. Bipolar Electrosurgery
Active and return electrode are on the instrument together
eliminates risk of capacitive coupling and alternate current pathways
lower power requirements needed secondary to high concentration of current between the poles
So…..use unmodulated current with low peak to peak voltage
Therefore, only dessication and coagulation possible

25. Bipolar Electrosurgery
Able to grasp and compress blood vessels
Able to dessicate tissue that is immersed in fluid
Limited to small “bites of tissue”, large pedicles not ideal
May have increased thermal spread than monopolar

26. Bipolar Current

27. Conclusions Keep active electrode clean, carbon impedes current flow
Know your instruments!!!
Remember Ohm’s law
Think :-)