Ch. 15 Electrosurgery and Lasers Flashcards
Voltage (V)
difference in potential between two points
Will drive charged particles across a potential difference
Electrical current (I)
flow of electrical charges and measured in amperes
Resistance (R)
impedance and measured in Ohms
A material property
V = IR
current is directly proportional to voltage and inversely proportional to resistance
W = VI
power or watts is equal to voltage times current
What current does electrosurgery work in
500 kHz
Pure cut electrosurgery: what kind of current and what wattage should be used?
Uninterrupted current
50-80 watts
Pure coagulation electrosurgery: what kind of current and what wattage?
Interrupted current
30-50 watts
Surgical diathermy
ability of electricity to form heat in living tissue
What factors influence thermal effects on tissue?
- watts
- electrode dwell time (length of exposure)
- contact type of the tissue to the active electrode
- the current
- tissue impedance
At what temperature will collagen be heated and its intramolecular cross links broken?
50-70 degrees celsius
At what temperature does tissue desiccation occur?
90 degrees celsius
cellular water completely evaporates
At what temperature will tissues be destroyed by cell wall rupture from the volumetric explosion of superheated steam? And what is this process called?
100 degrees celsius
Vaporization
At what temperature will tissue carbonization from dehydration occur?
250 degrees celsius
What temperature will cause inflammation and edema in tissues?
40 degrees celsius
At what temperature will enzymatic activity become inactivated?
50 degrees celsius
What is fulgration coagulation?
Holding the electrode slightly away from the tissue using coagulation mode, which results in an arc jumping the gap between the electrode and tissue.
The arc takes the form of a spark, which strikes the tissue in a dispersed and random pattern
High voltage sparking results in high temp tissue change and creates a superficial coagulum instead of vaporizing the tissue
Good for when a discrete bleeder cannot be found
But produces larges amounts of smoke as char forms and has deeper necrosis and thermal spread than cutting
What is desiccation coagulation?
Direct contact using coagulation mode
heats tissue more efficiently than fulgration and can have deeper necrosis and thermal spread
What is coaptive coagulation?
A type of desiccation coagulation
Metal instrument holds vessel
Heat denatures the adventitia, dehydrates the vessel, and blood flow stops
What is the maximum diameter vessel that Monopolar electrosurgery can coagulate?
2 mm in diameter
What is insulation failure in regards to electrosurgery with laparoscopic coagulation?
This occurs when there is damage or a defect to the material covering the active electrode
The active current may escape through this area and cause injury to adjacent organs
It is especially dangerous if the insulation failure is beyond the view of the scope
What is direct coupling in regards to dangers of electrosurgery?
This is when an active electrode is in direct contact or close proximity to another metal instrument or trocar
Activation of the electrode may cause transfer of the electrical current to the adjacent metal object
What is capacitive coupling?
This is when two conductors or instruments are separated by an insulator and form stored energy
then this can transfer to an adjacent conductor such as an outer cannula of the trocar sheath
How does the Harmonic electrosurgical device work?
There is no transfer of electricity to or through the patient
Ultrasonic waves made at 55,500 vibrations
This causes an oscillating saw effect along with heat and coagulation
Uses lower temperatures - 50 to 100 degrees celsius
the vessels seal by a protein coagulum (but other electrosurgery and lasers use burning to coagulate at 150 to 400 degrees celsius)
Seals vessels less than 3 mm
LASER
Light Amplification of Stimulated Emission of Radiation
How does LASER work?
An external source of energy stimulates particles into a high energy state
When the particles revert to their original state, energy is released in the form of photons that travel in the same waveform (monochromic) and move parallel to (spatial coherence) and in phase with (temporal coherence) each other in a linear (collimated) direction
Photons producing a laser beam have consistent energy released at the same wavelength, amplitude, frequency, and time
PD = watts/cm^2
Power density is directly proportional to the power (watts) that a laser can deliver and inversely proportional to the surface area that the beam strikes
Usually we talk about the surface area as a circle, so pi*r^2
This is called “spot size”
What is focal length in regards to laser?
The distance from the aperture to the laser’s highest power intensity
most focal lengths are 1-3 mm
With energy in the form of a laser, what four basic interactions can occur with tissue?
Of those four, which is the key to effective laser to tissue interaction?
Absorption, transmission, scatter, and reflection
Absorption is the key to effective laser to tissue interaction
What is tissue ablation with regards to lasers?
photoablation = direct breakage of molecular bonds
What wavelengths will penetrate tissues several mm?
Shorter wavelengths like Nd:YAG 1064 nm or diode 810 nm. These lasers are poorly absorbed by water and react more with pigments in the tissues
By contrast, CO2 laser works at 10,600 nm, Ho:YAG 2100 nm, and erbium:YAG 2940 nm
Characteristics of CO2 laser
10,600 nm
long wavelength means it can strongly react with and be absorbed by cellular water
produces effects through instantaneous heating of intracellular water to the boiling point
used for cutting and vaporization of tissue
at the laser-tissue interphase, vessels less than 0.6 mm can be sealed
Characteristics of Ho:YAG laser
2100 nm
highly absorbed by water
used in arthroscopic procedures because it causes minimal tissue necrosis
used for lithotripsy
laser will absorb water from the urolith and then a photothermal fragmentation of the stone occurs
Characteristics of Er:YAG laser
2940 nm
an infrared wavelength that is strongly absorbed by water and hydroxyapatite
can be used to cut bone
Characteristics of Nd:YAG laser
1064 nm
tissue penetration is deep
slightly absorbed by water and this allows tissue penetration up to 5 mm
coagulate larger blood vessels but also leads to a larger coagulation zone and damage to adjacent tissue
Characteristics of a diode laser
590 to 5300 nm but usually for vet med around 810-980 nm
not easily absorbed by water so this leads to a greater depth of thermal injury… greater peripheral tissue heating
can be used with a variety of delivery fiber tips and used for feline onychectomy, removal of dermal, subdermal, and oral masses
Characteristics of an argon laser
488-514 nm
visible blue green light that is highly absorbed by hemoglobin, therefore making it useful for the removal of vascular lesions
mainstay for controlling intraocular hemorrhage and are used for coagulation, vaporization and cutting in a bleeding environment
expensive
produces less charring
Characteristics of excimer laser
193 nm
ultraviolet laser used in ophthalmic surgery
“excited dimer”
excimer laser adds enough energy to disrupt the molecular bonds of the surface tissue without causing water vaporization
depth of 1 mm
what is used for LASIK surgery
