cryosurgery and electrosurgery

Question 1

indications for cryosurgery

Answer 1

cutaneous

oral

ocular

removal of many benign and neoplastic lesions

Question 2

contraindications for cryosurgery

Answer 2

bone lesions or masses located adjacent to the auricular cartilage

Question 3

cryosurgery principles

Answer 3

normal mammalian cells destroyed at -20C, cancer cells more resistant to freezing

rapid freezing is best

two freeze/thaw cycles are recommended for best efficacy

Question 4

primary injury

Answer 4

initiated by formation of intra- and extracellular ice crystals

intra-rupture cellular membrane

extra-cause dehydration, lethal intra electrolyte and pH changes

Question 5

secondary injury

Answer 5

due to vascular stasis

increased vascular permeability–>local hemoconcentration

endothelial damage–>thrombus formation–>tissue ischemia

Question 6

why rapid freezing

Answer 6

results in more intracellular crystal

slow thaw after freezing allows for recrystallization–>as crystals grow, cause more cellular damage

two freeze/thaw cycles produce most reliable tissue necrosis precooled tissue will freeze faster than normal tissue

Question 7

tissue considerations

Answer 7

dont use on highly vascularized tissues, dry tissues, for destruction of nerves

Question 8

cryogens

Answer 8

liquid nitrogen, nitrous oxide, carbon dioxide

stored in liquid form in dewar flasks

use caution when handling

Question 9

equipment-sprays

Answer 9

self pressurized spray guns deliver a mixture of cryogen vapor and droplets

most effective method of delivery

volume and size of droplet controlled by needle size and trigger

avoid runoff of liquid onto surrounding normal tissue

Question 10

equipment-hollow probes

Answer 10

hollow probe chilled by circulation liquid that then exits under pressure through a small opening

easier to control, slower rate of cooling

contact or penetration (use bx core)

Question 11

equipment solid probe

Answer 11

chilled by immersion in cryogen liquid

used for contact freezing

very efficient coolling

multiple probes may be used in rotation for faster sx time for large or multiple tumors

Question 12

procedure

Answer 12

clip hair, remove gross debris

local or regional anesthesia

two freeze/thaw cycles (ex: 5 min freeze, 20 min thaw, 3 min freeze)

Question 13

depth of freeze

Answer 13

objective measurement with pyrometer

subjective evaluation of ice ball (visible/palpable)

depth of contact freezing 1/2 the radius of the ice ball

Question 14

normal response to freezing

Answer 14

swelling due to increased vascular permeability and vasodilation-occurs within hr, self limiting resolves in 48 h

increased bleeding of bx or ulcerated tissue due to local vasodilation

necrosis occurs in 14-21d, offensive odor, daily cleaning, +/- removal of necrotic tissue

Dry eschar formation over area of necrosis-

pigmentation and hair loss

Question 15

potential applications

Answer 15

cutaneous masses-eq sarcoids, SCC, Melanomas, Skin tags, wards

ocular tumors-SCC, etc, must protect cornea

solid organ tumors

disticia

retinal detachment

selected lameness issues in the horse-splints, nerving for navicular syndrome

Question 16

electrosurgery

Answer 16

radiofrequency current used for incision, coagulation, dessication, fulguration

Question 17

fulguration

Answer 17

destruction of tissue by means of a high frequency electrical current

does not actually touch tissue

only used on superficially damage or destroy diseased tissue that cannot be fully excised

Question 18

dessication

Answer 18

drying out tissue by removal of water

tip fo electrode contacts tissue

only used on superficially damage or destroy diseases tissue that cannot be fully excised

Question 19

high power and low voltage

Answer 19

cuts

Question 20

low power and high voltage

Answer 20

denature and coagulate

Question 21

use ________ probe with the _________ amount contact time to get desired effect

Answer 21

smallest, minimal

Question 22

electrical burns

Answer 22

potential complication

occurs if there are any breaks in the insulation

Question 23

Electrosurgery Equipment

Answer 23

monopolar or bipolar instruments

Question 24

monopolar

Answer 24

most commonly used

can cut, coagulate

must be dry environment-tissue hemorrhage creates difficulties

important that current exit through a large volume ot tissue to prevent pathway burns (ie under body, not a limb)

Question 25

bipolar electrosurgery

Answer 25

tissue forceps are the active electrode

current passes from one tip through the tissue to the opposite tip

less current, no ground plate, less collateral damage, can use in wet surgical field

Question 26

what must not happen to the bipolar electrosurgery forceps?

Answer 26

the tips must have continuity of electrolyte fluid and tips must not come in contact with each other

Question 27

electrosurgery cutting

Answer 27

cells vaporized along line of incision in 1 tissue plane

cuts all tissue it contacts-never use blind

use modified pencil grip with tip perpendicular to the tissue

Question 28

electrosurgery cutting technique

Answer 28

place tissue under tension

use lowest setting that allows for clean cutting

keep electrode clean

Question 29

electroincision advantages

Answer 29

reduces blood loss

decreases need for ligatures-reduced foreign material

reduced operating time

Question 30

electroincision disadvantages

Answer 30

thermal necrosis at edges

depth less precise

delayed wound healing

decreased resistance to infection

can ignite or explode if used in presence of ether, alcohol or bowel gases

Question 31

electrosurgery coagulation

Answer 31

heat from high-frequency electrical current causes protein denaturation inside tissue cells

coagulates vessels up to 2 mm diameter

if too high- intracellular fluid will boil and vessel may break

Question 32

obliterative coagulation in electrosurgery

Answer 32

direct contact between the electrode and the vessel,

vessel wall shrinks

lumen occluded by thrombosis and coagulum formation

Question 33

coaptive coagulation in electrosurgery

Answer 33

vessel clamped with forceps, electrode contacts instruments and energy is conducted to vessel

destroys adventitia and shrinks smooth muscle layers

intima flattened by pressure of clamp and fuses

more precise technique

Question 34

arthroscopic electrosurgery

Answer 34

useful for cutting soft tissue

avoid contact with cartilage and bone

use with caution

Question 35

ligasure

Answer 35

energy based vessel sealing and ligation method with internal guilltoine for cutting sealed tissue

up to 7 mm vessels

expensive