Chapter 14 - Cryosurgery Flashcards
At what temperature does liquid nitrogen operate?
A) −196°C B) −20°C C) −40°C D) −89°C
A) −196°C
What temperature range is critical for tissue thawing during cryosurgery?
A) −30°C to −20°C B) −25°C to −20°C C) −40°C to −30°C D) −15°C to −10°C
B) −25°C to −20°C
What is the typical temperature a cryosurgery probe can cool down to?
A) −20°C B) −40°C C) −89°C D) −196°C
C) −89°C
What percentage of cells are affected by cryonecrosis in high-water content tissues?
A) 100% B) 75% C) 50% D) 90%
A) 100%
How many freeze-thaw cycles are optimal for maximal tissue destruction?
A) 1 B) 2 C) 3 D) 4
B) 2
What is the primary cryogen used in equine medicine?
A) Carbon dioxide B) Gaseous nitrous oxide C) Liquid nitrogen D) Helium
C) Liquid nitrogen
What is the initial suggested temperature and duration for tissue destruction?
A) −30°C for 1 minute B) −20°C for 1 minute C) −20°C for 5 minutes D) −10°C for 10 minutes
B) −20°C for 1 minute
What percentage of horses showed regression of untreated sarcoids after treatment with cryosurgery?
A) 100% B) 50% C) 75% D) 90%
C) 75% (implied as significant but not explicitly stated)
How much higher temperature do peripheral lesions typically reach during cryosurgery?
A) 5°C B) 10°C C) 15°C D) 20°C
B) 10°C
What is the cooling capability of nitrous oxide in terms of temperature?
A) −196°C B) −89°C C) −40°C D) −20°C
B) −89°C
What is the maximum exposure temperature for cancer cells to ensure cell destruction using the double-freeze protocol?
A) −20°C B) −30°C C) −40°C D) −50°C
C) −40°C
What is the mechanism of injury from freezing that causes immediate cell death?
A) Endothelial damage B) Ice crystal formation C) Vascular stasis D) Recrystallization
B) Ice crystal formation
What happens to ice crystals during thawing at temperatures between −25°C and −20°C?
A) They freeze more B) They fuse to form large crystals C) They disappear D) They expand in size
B) They fuse to form large crystals
What temperature is suggested for optimal cryoablative dose in tumors?
A) −10°C B) −20°C C) −30°C D) −40°C
C) −30°C
What is a potential drawback of using contact freezing with solid probes?
A) It cools too quickly B) It is difficult to control C) It warms up quickly in contact with tissue D) It doesn’t freeze tissue
C) It warms up quickly in contact with tissue
What can cause inadvertent frost lesions during cryosurgery?
A) Too much liquid nitrogen dripping down B) Using a cold probe C) Prolonged freezing time D) Direct contact with the skin
A) Too much liquid nitrogen dripping down
What type of cell is more sensitive to cryonecrosis due to its high mitotic rate?
A) Fibrocytes B) Epithelial cells C) Muscle cells D) Nerve cells
B) Epithelial cells
hat causes progressive microcirculation failure after thawing?
A) Cryogenic agents B) Ice crystal formation C) Endothelial damage D) Rapid freezing
C) Endothelial damage
How does the cryogen nitrous oxide compare to liquid nitrogen in terms of cooling temperature?
A) Nitrous oxide is colder B) They are the same C) Nitrous oxide is warmer D) Liquid nitrogen is much colder
D) Liquid nitrogen is much colder
How much higher is the thermal conductivity of tissue after the first freeze cycle?
A) 10% B) 20% C) 30% D) 40%
B) 20%
What percentage of patients required lower temperatures to destroy tumor cells than initially suggested?
A) 50% B) 60% C) 70% D) 80%
C) 70%
How many times should the freeze-thaw cycle be repeated for optimal effectiveness?
A) Once B) Twice C) Three times D) Four times
B) Twice
What type of lesions are best treated with nitrous oxide?
A) Large tumors B) Small cutaneous lesions C) Internal tumors D) Deep tissue lesions
B) Small cutaneous lesions
What should be avoided when using open-cell foams during cryosurgery?
A) They conduct heat well B) They absorb the cryogen C) They are inexpensive D) They provide insulation
B) They absorb the cryogen
What condition is specifically treated with cryosurgery in equine medicine?
A) Osteoarthrosis B) Proximal suspensory desmitis C) Equine sarcoids D) Fractures
C) Equine sarcoids
What is the benefit of using spray systems over contact probes?
A) They are easier to control B) They can freeze larger areas C) They are less expensive D) They remove more heat from the tissue
D) They remove more heat from the tissue
What does cryonecrosis particularly affect in high-water content cells?
A) Membranes B) Nuclei C) Organelles D) Cytoplasm
C) Organelles
How does the cooling rate affect the formation of intracellular ice crystals?
A) Faster cooling increases crystal formation B) Slower cooling increases crystal formation C) No effect D) It only affects extracellular crystals
A) Faster cooling increases crystal formation
What happens during the thawing phase that exacerbates cell damage?
A) Water enters damaged cells B) Cells rehydrate C) Increased blood flow occurs D) Crystals dissolve completely
A) Water enters damaged cells
What percentage of the cryosurgical technique focuses on avoiding damage to surrounding tissue?
A) 30% B) 50% C) 70% D) 100%
C) 70%
What is the impact of lower temperatures on cancer cell destruction?
A) No impact B) Increased effectiveness C) Decreased effectiveness D) Only affects normal cells
B) Increased effectiveness
How long should cells be exposed to −30°C to achieve destruction?
A) 1 minute B) 2 minutes C) 5 minutes D) 10 minutes
A) 1 minute
What factor affects the variation in cooling rates within a tumor?
A) Tumor size B) Proximity to the probe C) Type of cryogen used D) Depth of the lesion
B) Proximity to the probe
What is the ideal application method for large lesions?
A) Single chilled probe B) Multiple chilled probes C) Direct pouring D) Hand-held spraying
B) Multiple chilled probes
What is a common issue when too much liquid nitrogen is applied?
A) Increased efficacy B) Less effective freezing C) Frost lesions on adjacent skin D) Immediate evaporation
C) Frost lesions on adjacent skin
How does cryosurgery potentially stimulate the immune system?
A) By directly killing all cells B) Through cellular apoptosis C) By preserving healthy tissue D) Via changes in tissue composition
D) Via changes in tissue composition
What was a historical use of cryosurgery in the 1970s?
A) Only for skin lesions B) For tumors and pain relief C) Exclusively for equine sarcoids D) None of the above
B) For tumors and pain relief
What issue arises from using gauze swabs with cryogenic agents?
A) They freeze too quickly B) They can become cold sinks C) They cause additional injury D) They do not absorb enough cryogen
B) They can become cold sinks
hat percentage of tumor cells might not experience the same cooling and thawing temperatures?
A) 100% B) 50% C) 30% D) Varies greatly
D) Varies greatly
At what temperature can vacuum-insulated small-diameter probes be supercooled to?
A) −100°C B) −150°C C) −200°C D) −250°C
C) −200°C
How long does complete sloughing of necrotic tissue take after cryosurgery?
A) 1 to 2 weeks B) 2 to 4 weeks C) 4 to 6 weeks D) 6 to 8 weeks
B) 2 to 4 weeks
What is the typical duration for local edema to develop after thawing?
A) Immediately B) 12 hours C) 24 to 48 hours D) 72 hours
C) 24 to 48 hours
What margin is customary for the ice ball around ocular lesions?
A) 1 mm B) 2 to 3 mm C) 5 to 10 mm D) 10 to 15 mm
B) 2 to 3 mm
What temperature is typically reached at the outer edge of the hyperechoic rim (HER) during ultrasound monitoring?
A) −5°C B) 0°C C) −15°C D) −30°C
B) 0°C
How much time does coagulation necrosis take to develop after thawing?
A) 1 to 2 days B) 3 to 5 days C) Several days D) Immediate
C) Several days
What percentage of cryosurgery complications are significant due to technique application?
A) 5% B) 15% C) 25% D) 50%
A) 5%
What is the advised overlap when performing cryosurgery on larger tumors?
A) 1 mm B) 2 mm C) 3 mm D) 5 mm
B) 2 mm
How long can necrotic eschar take to detach from underlying tissue post-cryosurgery?
A) 1 week B) 2 weeks C) 3 weeks D) 4 weeks
C) 3 weeks
What is the tissue temperature at the border between the HER and hypoechoic frozen tissue?
A) −5°C B) −15°C C) 0°C D) −20°C
B) −15°C
How many thermocouple needles are advised for accurate temperature monitoring?
A) 1 B) 2 C) Several D) None
C) Several
What percentage of patients experience limited complications if cryosurgery is applied correctly?
A) 90% B) 75% C) 50% D) 25%
A) 90%
How long may excessive sloughing of tissue take, potentially leading to joint penetration?
A) 1 to 2 weeks B) 2 to 3 weeks C) 3 to 4 weeks D) Months
D) Months
What is the typical size of the lesions cryosurgery can treat without requiring multiple probe applications?
A) Less than 1 cm B) Up to 2 cm C) Up to 3 cm D) More than 3 cm
B) Up to 2 cm (implied from probe sizes)
What is a significant risk when freezing tissues near joints?
A) Muscle strain B) Joint sepsis C) Skin irritation D) Hair loss
B) Joint sepsis
What is the normal outcome of tissues that are correctly frozen?
A) Immediate healing B) Local necrosis C) Immediate sloughing D) No visible changes
B) Local necrosis
What occurs during the first 24 to 48 hours after tissue thawing?
A) Necrosis B) Hemorrhage C) Local edema D) Tissue regeneration
C) Local edema
What is the characteristic appearance of frozen tissue under ultrasound?
A) Hyperechoic B) Hypoechoic C) Anechoic D) Isoechoic
B) Hypoechoic
What temperature must be reached for effective cryotherapy in tissues?
A) −5°C B) −15°C C) −30°C D) −40°C
C) −30°C
What happens to melanocytes and hair follicles after cryosurgery?
A) They regenerate quickly B) They are destroyed C) They become hyperactive D) They disappear temporarily
B) They are destroyed
What is the potential benefit of monitoring ice ball formation ultrasonographically?
A) Reducing cost B) Ensuring proper freezing C) Avoiding pain D) Enhancing visibility
B) Ensuring proper freezing
How much bleeding can be expected from lesions that have been debulked?
A) None B) Limited C) Profuse D) Moderate
B) Limited
What can excessive freezing result in near joints?
A) Increased flexibility B) Decreased circulation C) Fibrous reactions D) Enhanced healing
C) Fibrous reactions
What happens to the boundary between frozen and unfrozen tissue?
A) It remains stable B) It is unclear C) It appears hyperechoic D) It disappears
C) It appears hyperechoic
How much higher can tissue temperatures be during cryotherapy?
A) 5°C B) 10°C C) 15°C D) 20°C
B) 10°C
What duration is necessary for monitoring the effectiveness of freezing?
A) 1 minute B) 5 minutes C) 10 minutes D) Continuous
D) Continuous (implied)
What is a typical reaction of tissues after cryosurgery?
A) Swelling B) Immediate scarring C) Total necrosis D) Rapid regeneration
A) Swelling
What happens to the tissue temperature as the ice ball extends beyond the lesion?
A) It decreases rapidly B) It stabilizes C) It remains constant D) It can reach critical levels
A) It decreases rapidly
What is an effective method to prevent cryosurgery complications?
A) Increase probe size B) Monitor temperatures accurately C) Use more cryogen D) Reduce freezing time
B) Monitor temperatures accurately
What is one of the critical roles of thermocouple needles during cryosurgery?
A) Aiding in anesthetic administration B) Monitoring peripheral temperatures C) Injecting cryogen D) Reducing bleeding
B) Monitoring peripheral temperatures
What is a common visual cue indicating that effective freezing has occurred?
A) Pale skin B) Ice ball formation C) Increased swelling D) Color change
B) Ice ball formation
What is essential for good contact when applying cryosurgery to lesions?
A) Sufficient probe size B) Cooling gel C) High pressure D) Frequent repositioning
A) Sufficient probe size
What might happen if the tissue temperature at the lesion’s edge does not reach appropriate levels?
A) Improved healing B) Risk of recurrence C) Reduced necrosis D) Increased strength
B) Risk of recurrence
What is the risk of using gauze swabs with cryogenic agents?
A) They absorb too much B) They can become cold sinks C) They dry out too quickly D) They cause tissue adhesion
B) They can become cold sinks
How long after cryosurgery may visible necrosis appear?
A) Immediately B) 24 hours C) 48 hours D) Days later
D) Days later
What is a major consideration when performing cryosurgery on the cornea?
A) Temperature monitoring is unnecessary B) Thermocouple placement can be risky C) Only superficial lesions can be treated D) Debulking is always required
B) Thermocouple placement can be risky
What happens to the tissue temperature at the border of the hypoechoic rim?
A) It stays constant B) It can be higher than −15°C C) It becomes anechoic D) It may decrease
B) It can be higher than −15°C
How should the cryosurgical probe be applied to ensure effective treatment?
A) In a single position B) With air gaps C) With firm contact D) With minimal pressure
C) With firm contact
What is one adverse effect that can result from excessive freezing of tissues?
A) Enhanced recovery B) Tissue preservation C) Damage to vital structures D) Increased pain
C) Damage to vital structures
What percentage of tumor cells may not be equally frozen during treatment?
A) 10% B) 25% C) 30% D) Varies greatly
D) Varies greatly
Figure 14-1. The Cryopen is a small hand-held device for gaseous nitrous oxide cryotherapy. It is easy to use but only suited for small cutaneous lesions and for ophthalmologic applications.
Figure 14-3. Spray cups come in a variety of sizes so that the cup can be fitted over a tumor, and as the spray is applied, droplets form a liquid pool contained by the cup. This prevents runoff generated by the spray method.
Figure 14-2. Special container used to deliver liquid nitrogen through a self-pressurizing spray gun. A thermocouple needle is to the left of the pyrometer, which is used to measure the temperature achieved in and beyond the limits of the targeted tissue.
Figure 14-4. Self-made PVC cup placed over a large debulked sarcoid on the inner thigh of a horse. The liquid nitrogen will be poured into the cup using a thermos flask. Thermocouple needles have been placed and a contact gel has been used to ensure good sealing between the cup and the skin.
Figure 14-5. Solid probes come in a variety of sizes, each fitted with a separate plastic handle that does not become chilled as the probe is immersed in liquid nitrogen.
Figure 14-7. Hollow liquid nitrogen circulation probe to which a conducting solid copper probe is attached, to provide continuous controlled freezing of a sarcoid lesion on the ventral abdomen. Contact gel and thermocouple needles have been used.
Figure 14-6. A special container is used into which liquid nitrogen is poured and the contact probe is immersed to attain the proper temperature before applying it to a lesion.
