cryosurgery and electrosurgery Flashcards
indications for cryosurgery
cutaneous
oral
ocular
removal of many benign and neoplastic lesions
contraindications for cryosurgery
bone lesions or masses located adjacent to the auricular cartilage
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
primary injury
initiated by formation of intra- and extracellular ice crystals
intra-rupture cellular membrane
extra-cause dehydration, lethal intra electrolyte and pH changes
secondary injury
due to vascular stasis
increased vascular permeability–>local hemoconcentration
endothelial damage–>thrombus formation–>tissue ischemia
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
tissue considerations
dont use on highly vascularized tissues, dry tissues, for destruction of nerves
cryogens
liquid nitrogen, nitrous oxide, carbon dioxide
stored in liquid form in dewar flasks
use caution when handling
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
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)
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
procedure
clip hair, remove gross debris
local or regional anesthesia
two freeze/thaw cycles (ex: 5 min freeze, 20 min thaw, 3 min freeze)
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
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
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
electrosurgery
radiofrequency current used for incision, coagulation, dessication, fulguration
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
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
high power and low voltage
cuts
low power and high voltage
denature and coagulate
use ________ probe with the _________ amount contact time to get desired effect
smallest, minimal
electrical burns
potential complication
occurs if there are any breaks in the insulation
Electrosurgery Equipment
monopolar or bipolar instruments
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)
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
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
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
electrosurgery cutting technique
place tissue under tension
use lowest setting that allows for clean cutting
keep electrode clean
electroincision advantages
reduces blood loss
decreases need for ligatures-reduced foreign material
reduced operating time
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
electrosurgery coagulation
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
obliterative coagulation in electrosurgery
direct contact between the electrode and the vessel,
vessel wall shrinks
lumen occluded by thrombosis and coagulum formation
coaptive coagulation in electrosurgery
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
arthroscopic electrosurgery
useful for cutting soft tissue
avoid contact with cartilage and bone
use with caution
ligasure
energy based vessel sealing and ligation method with internal guilltoine for cutting sealed tissue
up to 7 mm vessels
expensive
