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Surgery > Electrosurgery > Flashcards

Electrosurgery Flashcards

1
Q

Define electro-surgery

A
  • refers to the use of an alternating current that travels as a circuit through the patient to achieve the desired effect
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2
Q

Explain why a household current can cause electrocution while electro surgery does not?

A

standard electrical current alternates at 50-60 cycles per second
when interrupted this causes muscle stimulation
nerve and muscle stimulation ceases at 100,000 Hz
the electrosurgical generator increases the frequency to 200,000 Hz avoiding electrocution

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3
Q

Describe a bipolar circuit

A

two electrodes are placed at site of treatment
one acts as the active electrode, one as the return electrode
only the tissue that is grasped is included in the circuit

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3
Q

Describe a bipolar circuit

A

two electrodes are placed at site of treatment
one acts as the active electrode, one as the return electrode
only the tissue that is grasped is included in the circuitW

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4
Q

What is the benefit of bipolar circuit with regards thermal injury?

A

thermal injury is limited to spread to adjacent tissue

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5
Q

With a bipolar circuit, what is thermal spread dependent on?

A

TAP

  • time of application
  • amount of heat generated
  • power setting
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6
Q

Give an example of a piece of advanced bipolar equipment?

A
  • ligasure
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7
Q

What is the effect of the ligasure/advanced bipolar?

A

combination of heating and pressure leads to denaturation of collagen and cellular protein
desiccation and computation results (vessel sealing)

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8
Q

List 2 safety mechanism of advance bipolar

A
  • measures tissue resistance (impedance) to modify power use
  • as the amount of water in tissue decreases, resistance increases
  • tips of instruments remain relatively cool, tissue spread 2-3mm
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9
Q

Describe a monopolar circuit

A

active electrode is placed at the operation site

current passes through the body to the return electrode at a distant site

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10
Q

what is the disadvantage of a monopolar circuit with regards a thermal injury?

A

there is potential for thermal injury at distant sites

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11
Q

List 7 factors influencing the effect of a monopolar circuit?

A
  • waveform
  • contact vs spark
  • power setting
  • size of electrode
  • time
  • type of tissue
  • eschar
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12
Q

what is the ‘cutting’ waveform?

A
  • constant low voltage

- 100% on

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13
Q

what is the ‘coagulation’ waveform?

A
  • intermittent, high voltage current

- 6% on and 94% off

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14
Q

what is the ‘blend’ waveform?

A

modification of current

the greater the blend, the higher the pulse, and more ‘off’ the current

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15
Q

what is the effect of a constant waveform on tissue?

what is the effect of an intermittent waveform on tissues?

A

constant - vaporises tissues
intermittent - produces less heat and coagulates tissue

however any of the waveforms can cause vaporisation or coagulation depending on how they’re used/how it is applied to the tissue

16
Q

If using cutting waveform and use spark, what is the impact on tissue?

A

vaporisation

  • holding instrument away creates a spark
  • high heat over a short time - leads to vaporisation
17
Q

if using coagulation wave form and use spark to achieve desired effect - what is the effect on tissue?

A

fulguration

less heat over a wider area leads to the creation of a coagulum rather than vaporisation

18
Q

if using contact technique what is the impact on tissue?

  • for coag waveform?
  • for cutting waveform?
A
  • both produce same effect which is desiccation
  • the instrument touches tissue, the current concentration is reduced
  • less heat is generated and coagulation occurs , rather than vaporisation
19
Q

what is the biggest factor in the effect on tissue?

A

Contact vs spark

- as if contact then cutting and coag waveform do the same thing!

20
Q

which of the waveforms uses the least voltage?

A
  • cutting dose (low voltage constant, 100% on)

this is significant - as cutting can produce the same tissue effect (vaporisation or desiccation/coagulum formation) depending on whether spark or contact is used
and all this is achieved at a lower voltage than coag

21
Q

how does the size of the electrode impact on tissue effect for monopolar circuit?

A

size of electrode - if the electrode is tiny then the current concentration will be very high leading to a greater effect, if the electrode is very large (wide surface area) then vice versa

22
Q

what is an alternate site burn?

A

when the current finds an alternate way out of the body (ie not via the pad site)
if exit point is small enough then this will create a burn

23
Q

electrosurgical generators have developed over time to become safer, list a safety mechanism

A

since 1968 they have been isolated from the ground and the generator will not activate unless the current has returned via the diathermy plate
- this almost entirely prevents alternate site burns

24
Q

explain a pad site burn?

A

all the current entering a patient at the operative site leaves via the diathermy pad
if contact is poor and the surface area of the pad is small enough then a pad site burn will occur

25
Q

List 2 mechanisms to prevent a pad site burn?

A
  • return electrode monitoring
  • double pads
  • choosing a well vascularised muscle mass to place the pad (avoid bony prominences)
26
Q

describe direct coupling and how this can cause injury?

A
  • a second metal instrument is in contact with an organ (e.g. instrument in contact with bowel) and acts as an alternate route for the current
  • if contact is made between the active electrode and the second instrument then damage to organ/tissue (bowel) can occur
27
Q

describe capacitive coupling and how this can cause injury

A
  • occurs when a non conducting material separates 2 non conducting materials, an electrostatic field can be set up that transfers the current from one conductor to another
  • if the electrostatic field discharges onto tissue it can cause injury
28
Q

describe insulation failure and how this can cause injury

A
  • hole in the insulation around a electrode resulting in discharge of a Current through hole onto tissue
29
Q

List the risks of injury to tissue with monopolar diathermy?

A
  • direct coupling
  • capacitive coupling
  • insulation failure
  • direct thermal injury
30
Q

List methods to reduce risk of injury with electrosurgery

A
  • use lowest power setting
  • use lowest waveform (cutting)
  • inspect insulation
  • use intermittent activation
  • do not activate close to another instrument
  • never have two instruments in the patient (2 electrosurgical instruments)
  • always place instrument in quiver
  • use alternative e.g. harmonic scalpel
31
Q

How does a harmonic scalpel effect tissue?

A
  • using mechanical energy to cut and coagulate tissue
  • at 50-100 degrees it causes protein coagulation i.e. proteins disorganise to form a coagulum
  • at 100-150 degrees it causes tissue desiccation i.e. vaporisation of water desiccates tissue
  • at 150-400 degrees it causes eschar formation when tissues burn
32
Q

List 6 advantages of the harmonic scalpel

A
  • minimal thermal spread
  • dissection with cavitation
  • no charring or eschar
  • no neuromuscular stimulation
  • less smoke formation
  • no stray energy
  • hand activation
33
Q

what is cavitation?

A
  • transient low pressure created by vibration
  • causes the fluid to vaporise and cavitation results
  • cavitation opens up tissue planes assisting blood less dissection
34
Q

how does the harmonic scalpel actually work? i.e physics behind it

A
  • the electrical energy causes the piezo electric ceramics in the hand piece to expand and contract
  • in this manner electrical energy is transferred into mechanical energy
  • an ultrasound wave is created which travels along the shaft
  • the mechanical motion is amplified so that it is concentrated at the tip
35
Q

list 5 factors that influence the harmonic scalpel effect

A

TTBGP

  • time
  • tissue tension
  • blade sharpness
  • grip strength
  • power setting

Surgery (3 decks)

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