Ch. 15 Electrosurgery and Lasers

Question 1

Voltage (V)

Answer 1

difference in potential between two points

Will drive charged particles across a potential difference

Question 2

Electrical current (I)

Answer 2

flow of electrical charges and measured in amperes

Question 3

Resistance (R)

Answer 3

impedance and measured in Ohms

A material property

Question 4

V = IR

Answer 4

current is directly proportional to voltage and inversely proportional to resistance

Question 5

W = VI

Answer 5

power or watts is equal to voltage times current

Question 6

What current does electrosurgery work in

Answer 6

500 kHz

Question 7

Pure cut electrosurgery: what kind of current and what wattage should be used?

Answer 7

Uninterrupted current

50-80 watts

Question 8

Pure coagulation electrosurgery: what kind of current and what wattage?

Answer 8

Interrupted current

30-50 watts

Question 9

Surgical diathermy

Answer 9

ability of electricity to form heat in living tissue

Question 10

What factors influence thermal effects on tissue?

Answer 10

• watts
• electrode dwell time (length of exposure)
• contact type of the tissue to the active electrode
• the current
• tissue impedance

Question 11

At what temperature will collagen be heated and its intramolecular cross links broken?

Answer 11

50-70 degrees celsius

Question 12

At what temperature does tissue desiccation occur?

Answer 12

90 degrees celsius

cellular water completely evaporates

Question 13

At what temperature will tissues be destroyed by cell wall rupture from the volumetric explosion of superheated steam? And what is this process called?

Answer 13

100 degrees celsius

Vaporization

Question 14

At what temperature will tissue carbonization from dehydration occur?

Answer 14

250 degrees celsius

Question 15

What temperature will cause inflammation and edema in tissues?

Answer 15

40 degrees celsius

Question 16

At what temperature will enzymatic activity become inactivated?

Answer 16

50 degrees celsius

Question 17

What is fulgration coagulation?

Answer 17

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

Question 18

What is desiccation coagulation?

Answer 18

Direct contact using coagulation mode

heats tissue more efficiently than fulgration and can have deeper necrosis and thermal spread

Question 19

What is coaptive coagulation?

Answer 19

A type of desiccation coagulation
Metal instrument holds vessel
Heat denatures the adventitia, dehydrates the vessel, and blood flow stops

Question 20

What is the maximum diameter vessel that Monopolar electrosurgery can coagulate?

Answer 20

2 mm in diameter

Question 21

What is insulation failure in regards to electrosurgery with laparoscopic coagulation?

Answer 21

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

Question 22

What is direct coupling in regards to dangers of electrosurgery?

Answer 22

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

Question 23

What is capacitive coupling?

Answer 23

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

Question 24

How does the Harmonic electrosurgical device work?

Answer 24

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

Question 25

LASER

Answer 25

Light Amplification of Stimulated Emission of Radiation

Question 26

How does LASER work?

Answer 26

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

Question 27

PD = watts/cm^2

Answer 27

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"

Question 28

What is focal length in regards to laser?

Answer 28

The distance from the aperture to the laser's highest power intensity most focal lengths are 1-3 mm

Question 29

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?

Answer 29

Absorption, transmission, scatter, and reflection | Absorption is the key to effective laser to tissue interaction

Question 30

What is tissue ablation with regards to lasers?

Answer 30

photoablation = direct breakage of molecular bonds

Question 31

What wavelengths will penetrate tissues several mm?

Answer 31

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

Question 32

Characteristics of CO2 laser

Answer 32

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

Question 33

Characteristics of Ho:YAG laser

Answer 33

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

Question 34

Characteristics of Er:YAG laser

Answer 34

2940 nm an infrared wavelength that is strongly absorbed by water and hydroxyapatite can be used to cut bone

Question 35

Characteristics of Nd:YAG laser

Answer 35

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

Question 36

Characteristics of a diode laser

Answer 36

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

Question 37

Characteristics of an argon laser

Answer 37

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

Question 38

Characteristics of excimer laser

Answer 38

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