Electrosurgery Flashcards
What is electrosurgery?
Application of high radiofrequency electrical current to body tissue
Why is radiofrequency used?
High frequency so higher let go current threshold
- essential for safety
What is electrosurgery used for?
SURGICAL DIATHERMY
- cut tissue
- stop bleeding
- remove lesions
- benign skin tumors
- remove warts
How to change the effect in surgical diathermy?
Change the waveform delivered to the tissue
What equipment is used?
- Electrosurgical unit
- Active electrode/probe
- Dispersive/Passive electrode
What is an electrosurgical unit?
- high frequency electrical current generator
- plugged into main 50Hz
- converts 50Hz to high radiofrequency signal for surgery
What is the active electrode/probe used for?
Directly apply to surgical site
- applies the current
What is the dispersive/passive electrode used for?
- completes circuit for return current
What is the advantage over a scalpel?
- damages tissue considerably less
- can stop bleeding far better
What are some contraindications for electrosurgery?
PACEMAKER! as current will flow through
- any transplanted devices! (prosthetic joint)
Define diathermy
Therapeutic generation of local heat in body tissues by high-frequency electromagnetic radiation
- conversion of electromagnetic energy into thermal energy to heat tissues (P=I^2 x R)
Define shortwave diathermy
Radiowaves of 11m wavelength
Frequency of 27 mHz
Not a surgery device
Greater heat retention and efficient healing as larger treatment area
Uses of shortwave diathermy
Pain relief Reducing muscle spasm Decreasing joint stiffness Contractions Increasing blood flow
Uses of diathermy for musculo-skeletal disorders
- osteomyelitis
- strains & sprain
- tendonitis
- bursitis
- carbuncles
- capsule lesion
- subacute & chronic arthritis
- post-traumatic conditions (fracture/haematoma/contusion)
Uses of diathermy for cardiovascular disorders
- angina pectoris
- HTN
Uses of diathermy for chest disorders
Relieve muscle spasm in bronchial asthma
Subacute & chronic bronchitis
Uses of diathermy for neurological disorders
- neuritis
- sciatica
- migraine
Uses of diathermy for genitourinary disorders
- endometritis
- salpingitis
- ovaritis
Uses of diathermy for mouth and teeth disorders
- gingivitis
- cyst
Uses of diathermy for ENT disorders
- sinusitis
- laryngitis
Define electrocautery
- type of electrosurgery
- probe heated by DC to be very hot
- use to burn and cauterize tissue
- will denature proteins with high heat
- electricity used for heating effect
- tool could be heated by another means for same result
What are some principles of electrosurgery?
- need to make patient part of electronic circuit (current travels through probe tip and into patients and back out)
- patient creates high resistance part of circuit (large voltage drop and its heating effect occur within the patient)
How does P relate to I and V?
P = IV
What is the current density?
- AC used to heat tissue directly
- tip of probe remains cool
- larger resistance = greater current density
- same current through smaller area = greater current density = greater heat
What is the effect of electrosurgery <45 degrees C?
Thermal damage to tissue is reversible
What is the effect of electrosurgery >45 degrees C?
Denature of proteins (intracellular & extracellular) = coagulation
- damage irreversible
What is the effect of electrosurgery >90 degrees C?
- liquid in tissue evaporates
- results in either desiccation (if heat tissue slowly) or vapourisation (if heat tissue quickly)
What is the effect of electrosurgery >200 degrees C?
Everything turns to carbon
What is the frequency range of electrosurgery?
200kHz - 5MHz
- above 100KhZ (electricity doesn’t stimulate nervous system)
What do electrosurgery modalities refer to?
- how you complete the electrical circuit
What are the 2 main methods/modalities?
- monopolar
- bipolar
Monopolar Electrosurgery
- most common method
- easiest to use & most versatile
- only 1 electrode at surgical site, passive electrode away from surgical site
Monopolar Electrosurgery Mechanism
- generator creates current
- enters patient through active electrode
- dispersive electrode for return current path to generator
How do we ensure passive electrode is not functioning?
Make sure it is grounded
- placed where there is low resistance
How do we make sure active electrode has high current density?
Tip is pointed = smaller area = greater heat
NOTE: Current is still the same in whole circuit, even though density is different due to resistance
Bipolar Electrosurgery
Slightly more difficult
Safer Generally
2 electrodes
Mechanism of bipolar electrosurgery
- generator creates current
- enters patient through active electrode
- small piece of tissue gripped in forceps (current only travels through this & back to generator)
Why is bipolar electrosurgery safer?
Current only confined to small area (small piece of tissue and 2 electrodes)
- doesn’t go across patient’s body
What are the benefits of electrosurgery?
- anaesthesia is not always necessary for small lesion electrosurgery (short bursts of low power current may be less uncomfortable)
- can use mixture of local anaesthetics (EMLA) cream for small lesions (much safer than general/injected anaesthetic & very simple to use)
- injectable lidocaine suitable before most more extensive electrosurgical techniques
What is the purpose of lidocaine?
- with epinephrine = further reduces blood loss
- no need for general anaesthetic
- do not use epinephrine at tips of digits or nose
What is the most common source of operating room fires & explosions?
- electrosurgical devices
What are the risks associated with explosions & fire?
ANESTHESIA EQUIPMENT
- ignite gaseous anaesthetics
- paper/cloth/flammable liquids
- betadine (70% alcohol)
- electrosurgical devices
What are some precautions to take when thinking about explosions & fire hazards?
- keep equipment away from flammable surroundings
- avoid preparing skin with alcohol
- avoid highly flammable anaesthetics
- do not use oxygen simultaneously
What precautions to take when thinking about electrical shock & burns?
- control the flow of current through the patient
- monopolar is more dangerous than bipolar
- any high resistance in the current path will lead to heating
- require high resistance at active electrode contact & low resistance at the return electrode
Dispersive Electrode
- large SA = reduced current density
- low resistance
- excellent contact between return electrode & patient’s skin
- must be placed on well vascularised muscle tissue (for low resistance as lots of liquid with ions which help currents move) (NOT UNDER BONY PROMINENCE)
How can excellent contact of the electrode be compromised?/How can surface area impedance be increased?
- excessive hair
- adipose
- bony prominences
- presence of fluid/lotions
- scar tissue
What does BURN =?
BURN = (HEAT x TIME) / AREA
What is the contact quality monitoring system?
- SAFETY METHOD
- monitors the resistance in the circuit
- detects large resistance and abnormal current variations
- will stop generator providing any current to patients if high level of impedance at patient/pad interface
- will eliminate hazards of return electrode or alternate site burns
- monitors return electrode contact quality and therefore resistance of it
- actively monitors impedance amount at patient/pad interfae
What proportion of electrosurgery injuries do burns account for?
70%
When is the contact quality monitoring system deactivated?
- if the patient return electrode path is broken
What are the modes of operation of the electrosurgery unit?
- CUT
- COAGULATE
- BLEND
How does the BLEND mode work?
CUT & COAGULATE together by manipulating factors
- waveform
- power
- electrode size
- time
- electrode positioning
- tissue type
- eschar
What are the 2 most important factors to manipulate?
- waveform and power
- changing these changes heat and regulates between cutting and coagulating
CUTTING mode features
- continuous high frequency alternating sine waves
- high frequency
- high current = lower voltage
- 1300-2300V
- power 50-80W
- local intense heating which vaporizes tissue
- minimal coagulation (hemostasis)
CUTTING mode method
- electrode held away from tissue
- creates a spark gap or steam envelope through which current arcs to the tissue
- maximises current intensity
- rides on a vapour film as it moves through the tissue
- heating up the atmosphere between the electrode & tissue
Types of electrode tip in cutting mode
Fine needles Wire Loop Diamond Ellipse Triangle
What is the power level in cutting method?
Relatively low
- minimal charring & tissue damage
- stops effect spreading
Advantages of cutting mode
- clean margins and wound healing
- cells only few layers deep remain undamaged
- thermal energy lost in latent heat of evaporation of cell contents (>100 degrees C but not as high as 200)
- power drops very quickly when point moves down to tissue
- ## low power = minimal tissue damage
Coagulation Mode Features
- intermittent bursts of radiofrequency sine waves
- 6% of the time is electrocurrent being applied
- tissue heated when waveform spikes (proteins denature)
- tissue cools between spikes
- high voltage (3500-9000V, few X higher than cutting)
- low current
- lower power 30-50W
- spikes of voltage at 9000V at 50W
- necessary for current to pass through highly resistant, desiccated tissue
- effect depends on amount of power dissipated (I^2R)
Coagulation Mode Method
- active electrode touching skin
- forceps often used as active electrode to grip the required tissue = heat sealing
- electrode shaped as 2-5mm metallic sphere (not as pointed)
- temp around 55 degrees C ( protein denaturisation)
- good for clotting small vessels (less than 2-3mm)
- can cut tissue at high power but charring & tissue damage likely
Blending Mode
- if haemostasis is needed while cutting
- total energy remains the same
- ratio of voltage & current modified to increase haemostasis during dissection
- discontinuous waveform by interrupting current & increasing voltage
What are the different BLENDING variations?
1,2 and 3
Higher setting = more time between bursts of current -> greater coagulation
BLENDING 1 variation
80% cut
20% coagulation
BLENDING 2 variation
60% cut
40% coag
BLENDING 3 variation
50% cut
50% coag
What determines if a waveform vaporizes or produces a coagulum?
- rate at which heat is produced
- VAPORIZATION = high heat produced rapidly
- COAGULUM = low heat produced more slowly
What are some other methods of altering output?
- electrode size
- time
- electrode positioning
- eschar
How does electrode size affect output?
- small electrode = high current density = concentrated heating at contact
How does time affect output?
- long treatment = more heat travels through body
- too long = wider & longer tissue damage
- too litt;e = absence of desired effect
How does electrode positioning affect output?
- direct contact with tissue = coagulation
- sparking to tissue = vaporization
How does tissue type affect output?
- tissues have different electrical resistances
- adipose + bone = high resistance and poor electrical conductors
- muscle + skin = good conductors + low resistance
How can eschar affect output?
- scab formed when wound/skin sealed in electrosurgery
- high resistance to current
- must not build up as will cause power loss instead of tissue
What is an example of tissue response technology?
- constant output power
- consistent tissue effect
- requires continuous adjustment of voltage
- feedback circuit as tissue liquid evaporates and then tissue resistance increases maintaining consistent power
- constant heating effect
Treatment modalities
Electrosection
Electrocoagulation
Electrofulguration
Electrodesiccation
Electrosection
Pure cutting waveform
- continuous high current density
- just on skin surface
- vapourisation of cells
Electrocoagulation
- also called coaptive coagulation or white coagulation
- coagulation waveforms
- huge range of waveforms
- 6% duty cycle on
- high voltage, low current
Electrofulguration
- to ablate or remove tissue
- e.g. cancerous tissue, superficial lesions, basal cell carcinoma
- specific waveform
- blend between electrosection and electrocoagulation
- also called black coagulation/spray coagulation
- active electrode held away from skin & arcs like cutting
- uses an intermittent waveform like coagulation
- waveform can be manipulated and altered
Electrodesiccation
- another form of coagulation
- use of different waveforms depending on heat required
- active electrode touching the skin to produce tissue destruction = deeper necrosis & thermal spread
- less current density & higher V
- lower powers than cutting otherwise damage would be severe
- cells dried to give coagulation
- intermittent waveform
- blend between 6% and 100%
Monopolar Electrosurgery Uses
- can cut and coagulate
- can cut, fulguration & dessication
- current density very large by probe tip
- current rapidly spread out laterally after it hits body
- within tissue direct travel of current or spark gap
Bipolar Electrosurgery Uses
- only treats gripped tissue
- mimises surrounding damage
- cannot be used for cutting
- can coagulate & fuse tissue
Laparoscopic electrosurgery Advantages
- combined with electrosurgery
- minimally invasive
- using endoscopy
- commonly abdomen
- minor procedures
- enables outpatient procedures
- short hospital stays
- lower hospital costs
- faster/more comfortable recovery
Laparoscopic electrosurgery Disadvantages
- additional safety concerns with electrosurgery
- limited field of view (electrode not visible)
- insulation failure
- direct coupling
Insulation Failure
In active electrode covering
- often out of view
- frequent re-sterilization of instruments can weaken/break insulation
- particularly a problem for coagulation waveform (high voltage output)
How to deal with insulation failure?
- lower current concentration by coagulating with a cutting current
- use an active electrode monitoring system
Direct Coupling
- direct coupling of electrode with other metal instruments used internally
- current can then flow through other instrument potentially to anywhere
How to deal with direct coupling?
- activate electrode only when fully visible & in contact with target tissue
- avoid using other instruments as much as possible
Capacitive Coupling
- stray current from electrode burns tissue
- capacitor creates an electrostatic field between the 2 conductors
- higher peak voltage = greater chance for capacitive discharge
How to deal with capacitive coupling?
- activate electrode only when it is in contact with target tissues
- limit time on coagulation setting (with high voltage peaks)
- use metal cannulas that allow stray current to be dispersed through the patient’s abdominal wall
- use different technology = insulation protective shells/layers
