cryosurgery and electrosurgery Flashcards Preview

Surgery and Anesthesia test 1 > cryosurgery and electrosurgery > Flashcards

Flashcards in cryosurgery and electrosurgery Deck (35)
Loading flashcards...
1

indications for cryosurgery

cutaneous

oral

ocular 

removal of many benign and neoplastic lesions

2

contraindications for cryosurgery

bone lesions or masses located adjacent to the auricular cartilage

3

cryosurgery principles

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

4

primary injury

initiated by formation of intra- and extracellular ice crystals

intra-rupture cellular membrane

extra-cause dehydration, lethal intra electrolyte and pH changes

5

secondary injury

due to vascular stasis

increased vascular permeability-->local hemoconcentration

endothelial damage-->thrombus formation-->tissue ischemia

6

why rapid freezing

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

7

tissue considerations

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

8

cryogens

liquid nitrogen, nitrous oxide, carbon dioxide

stored in liquid form in dewar flasks

use caution when handling

 

9

equipment-sprays

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

10

equipment-hollow probes

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)

11

equipment solid probe

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

12

procedure

clip hair, remove gross debris

local or regional anesthesia

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

13

depth of freeze

objective measurement with pyrometer

subjective evaluation of ice ball (visible/palpable)

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

14

normal response to freezing

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

15

potential applications

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

16

electrosurgery

radiofrequency current used for incision, coagulation, dessication, fulguration

17

fulguration

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

18

dessication

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

19

high power and low voltage

cuts

20

low power and high voltage

denature and coagulate

21

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

smallest, minimal

22

electrical burns

potential complication

occurs if there are any breaks in the insulation

23

Electrosurgery Equipment

monopolar or bipolar instruments

24

monopolar

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) 

25

bipolar electrosurgery

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

 

26

what must not happen to the bipolar electrosurgery forceps?

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

27

electrosurgery cutting

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

28

electrosurgery cutting technique

place tissue under tension

use lowest setting that allows for clean cutting

keep electrode clean

29

electroincision advantages

reduces blood loss

decreases need for ligatures-reduced foreign material

reduced operating time

30

electroincision disadvantages

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