Electrosurgery Flashcards
Define electro-surgery
- refers to the use of an alternating current that travels as a circuit through the patient to achieve the desired effect
Explain why a household current can cause electrocution while electro surgery does not?
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
Describe a bipolar circuit
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
Describe a bipolar circuit
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
What is the benefit of bipolar circuit with regards thermal injury?
thermal injury is limited to spread to adjacent tissue
With a bipolar circuit, what is thermal spread dependent on?
TAP
- time of application
- amount of heat generated
- power setting
Give an example of a piece of advanced bipolar equipment?
- ligasure
What is the effect of the ligasure/advanced bipolar?
combination of heating and pressure leads to denaturation of collagen and cellular protein
desiccation and computation results (vessel sealing)
List 2 safety mechanism of advance bipolar
- 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
Describe a monopolar circuit
active electrode is placed at the operation site
current passes through the body to the return electrode at a distant site
what is the disadvantage of a monopolar circuit with regards a thermal injury?
there is potential for thermal injury at distant sites
List 7 factors influencing the effect of a monopolar circuit?
- waveform
- contact vs spark
- power setting
- size of electrode
- time
- type of tissue
- eschar
what is the ‘cutting’ waveform?
- constant low voltage
- 100% on
what is the ‘coagulation’ waveform?
- intermittent, high voltage current
- 6% on and 94% off
what is the ‘blend’ waveform?
modification of current
the greater the blend, the higher the pulse, and more ‘off’ the current
what is the effect of a constant waveform on tissue?
what is the effect of an intermittent waveform on tissues?
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
If using cutting waveform and use spark, what is the impact on tissue?
vaporisation
- holding instrument away creates a spark
- high heat over a short time - leads to vaporisation
if using coagulation wave form and use spark to achieve desired effect - what is the effect on tissue?
fulguration
less heat over a wider area leads to the creation of a coagulum rather than vaporisation
if using contact technique what is the impact on tissue?
- for coag waveform?
- for cutting waveform?
- 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
what is the biggest factor in the effect on tissue?
Contact vs spark
- as if contact then cutting and coag waveform do the same thing!
which of the waveforms uses the least voltage?
- 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
how does the size of the electrode impact on tissue effect for monopolar circuit?
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
what is an alternate site burn?
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
electrosurgical generators have developed over time to become safer, list a safety mechanism
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
explain a pad site burn?
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
List 2 mechanisms to prevent a pad site burn?
- return electrode monitoring
- double pads
- choosing a well vascularised muscle mass to place the pad (avoid bony prominences)
describe direct coupling and how this can cause injury?
- 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
describe capacitive coupling and how this can cause injury
- 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
describe insulation failure and how this can cause injury
- hole in the insulation around a electrode resulting in discharge of a Current through hole onto tissue
List the risks of injury to tissue with monopolar diathermy?
- direct coupling
- capacitive coupling
- insulation failure
- direct thermal injury
List methods to reduce risk of injury with electrosurgery
- 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
How does a harmonic scalpel effect tissue?
- 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
List 6 advantages of the harmonic scalpel
- minimal thermal spread
- dissection with cavitation
- no charring or eschar
- no neuromuscular stimulation
- less smoke formation
- no stray energy
- hand activation
what is cavitation?
- transient low pressure created by vibration
- causes the fluid to vaporise and cavitation results
- cavitation opens up tissue planes assisting blood less dissection
how does the harmonic scalpel actually work? i.e physics behind it
- 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
list 5 factors that influence the harmonic scalpel effect
TTBGP
- time
- tissue tension
- blade sharpness
- grip strength
- power setting
