Electrosurgery

Question 1

Define electro-surgery

Answer 1

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

Question 2

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

Answer 2

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

Question 3

Describe a bipolar circuit

Answer 3

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

Question 3

Describe a bipolar circuit

Answer 3

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

Question 4

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

Answer 4

thermal injury is limited to spread to adjacent tissue

Question 5

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

Answer 5

TAP

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

Question 6

Give an example of a piece of advanced bipolar equipment?

Answer 6

• ligasure

Question 7

What is the effect of the ligasure/advanced bipolar?

Answer 7

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

Question 8

List 2 safety mechanism of advance bipolar

Answer 8

• 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

Question 9

Describe a monopolar circuit

Answer 9

active electrode is placed at the operation site

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

Question 10

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

Answer 10

there is potential for thermal injury at distant sites

Question 11

List 7 factors influencing the effect of a monopolar circuit?

Answer 11

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

Question 12

what is the ‘cutting’ waveform?

Answer 12

• constant low voltage

- 100% on

Question 13

what is the ‘coagulation’ waveform?

Answer 13

• intermittent, high voltage current

- 6% on and 94% off

Question 14

what is the ‘blend’ waveform?

Answer 14

modification of current

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

Question 15

what is the effect of a constant waveform on tissue?

what is the effect of an intermittent waveform on tissues?

Answer 15

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

Question 16

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

Answer 16

vaporisation

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

Question 17

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

Answer 17

fulguration

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

Question 18

if using contact technique what is the impact on tissue?

• for coag waveform?
• for cutting waveform?

Answer 18

• 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

Question 19

what is the biggest factor in the effect on tissue?

Answer 19

Contact vs spark

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

Question 20

which of the waveforms uses the least voltage?

Answer 20

• 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

Question 21

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

Answer 21

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

Question 22

what is an alternate site burn?

Answer 22

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

Question 23

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

Answer 23

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

Question 24

explain a pad site burn?

Answer 24

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

Question 25

List 2 mechanisms to prevent a pad site burn?

Answer 25

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

Question 26

describe direct coupling and how this can cause injury?

Answer 26

- 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

Question 27

describe capacitive coupling and how this can cause injury

Answer 27

- 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

Question 28

describe insulation failure and how this can cause injury

Answer 28

- hole in the insulation around a electrode resulting in discharge of a Current through hole onto tissue

Question 29

List the risks of injury to tissue with monopolar diathermy?

Answer 29

- direct coupling - capacitive coupling - insulation failure - direct thermal injury

Question 30

List methods to reduce risk of injury with electrosurgery

Answer 30

- 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

Question 31

How does a harmonic scalpel effect tissue?

Answer 31

- 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

Question 32

List 6 advantages of the harmonic scalpel

Answer 32

- minimal thermal spread - dissection with cavitation - no charring or eschar - no neuromuscular stimulation - less smoke formation - no stray energy - hand activation

Question 33

what is cavitation?

Answer 33

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

Question 34

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

Answer 34

- 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

Question 35

list 5 factors that influence the harmonic scalpel effect

Answer 35

TTBGP - time - tissue tension - blade sharpness - grip strength - power setting