Cryosurgery

Question 1

What is the mechanism of action for cryotherapy?

Answer 1

1. Extracellular dehydration from the formation of ice crystals in the extracellular space causing an extracellular hyperosmotic gradient that dehydrates adjacent cells
2. Membrane rupture from continued freezing that causes intracellular ice crystals which puncture the membrane
3. Vasoconstriction: initial freezing which compounds damage due to anoxia
4. Vasodilation: After thawing, compensatory vasodilation releases harmful free radicals into the affected tissue

Question 2

What is the boiling point of liquid nitrogen?

Answer 2

-196 degrees C

Question 3

What is the boiling point of solid carbon dioxide?

Answer 3

-76 degrees C

Question 4

At what temperature do melanocytes die?

Answer 4

-5 degrees C

Question 5

At what temperature do keratinocytes die at?

Answer 5

-20 degrees C to -30 degrees C

Question 6

At what temperature do fibroblasts freeze at?

Answer 6

-35-40 degrees C (least sensitive)

Question 7

At what temperature do most benign lesions need to be frozen to?

Answer 7

-25 degrees C

Question 8

To what temperature do malignant lesions need to be frozen to?

Answer 8

-50 degrees C

Question 9

What is the optimal freezing/thawing cycle?

Answer 9

Rapid freezing followed by slow thawing

don’t put your finger on a frozen area to get it to unthaw faster

Question 10

What are the 4 types of cryosurgery delivery?

Answer 10

• Open technique: most commonly performed; liquid nitrogen is released through tips, needles, cannulas, or cones
• Chamber technique: Modification of “open technique”; typically used only for malignancies cryogen is released into a chamber. The turbulence within the chamber leads to lower temperatures and faster than the open type
• Closed technique: Uses a probe to deliver the thermal insult; attached to the cryogen line and is a closed system
• Intralesional technique: Cryogen is injected directly into tissue via either a cannula or needle

Question 11

What is the open cryotherapy technique?

Answer 11

This is the most common type, canister with a nozzle that sprays liquid cryogen

Question 12

What is a semi-open technique of cryotherapy?

Answer 12

Confined spray using a cone, speculum of an otoscope, etc. Must use the right size of cone

Question 13

What is the semi-closed chamber method of cryotherapy and what is it good for?

Answer 13

It uses a metal chamber that is connected to the spray bottle on one end and rubber-tipped chamber on the other. Potent cryogen, used for skin cancers and cutaneous metastases

Question 14

What is a closed system of cryotherapy and what is it good for?

Answer 14

This is a metal chamber that circulates the cryogen but is not open. The cold metal of the chamber is pressed directly on the lesion –> rapid and potent freezing. Good for deep and fast freezing