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Proc Derm 2020 > Cryosurgery > Flashcards

Cryosurgery Flashcards

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1
Q

The basic cryosurgery principle is that of freezing cycles with subzero temperatures that result in sloughing of the damaged tissue and subsequent healing by secondary intention.

A

T

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2
Q

Subzero temperatures cause cell death due to

  • physical effect of direct cell injury with water crystallizing outside the cell
  • internal crystal formation with further freezing
  • vascular effects
  • immune changes targeting the damaged tissue
A

T

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3
Q

Tissues, including cancer cells can be destroyed at -20C

A

F

Cancer cells require -50 degrees C as more resistant but other tissues are destroyed at -20

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4
Q

With cryosurgery, necrosis occurs at the centre of the area of destruction where the temperature is consistently less than -10 degrees C

A

F

-40 degrees C

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5
Q

Slow freezing with rapid thawing is the ideal formula for cell destruction.

A

F

Rapid freezing and slow thawing.

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6
Q

The temperature of liquid nitrogen is -196 degrees C, which achieves ideal freezing temperatures needed to destroy malignancies.

A

T

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7
Q

Liquid nitrogen is stored in dewars, which are constructed with insulating material to provide long storage time

A

T

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8
Q

The goal of liquid nitrogen is to obtain temperatures of -50 degrees C to -60 degrees C at the periphery of the ice ball

A

T

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9
Q 
The various techniques of cryosurgery include: 
Open (or spray)
Semi-open (cones or plastic plate)
Closed (contact or probe)
Chamber = Semi-closed
Tweezers 
Intralesional
A

T

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10
Q

In the open cryosurgery technique, the cryogen is released from the unit through tips, needles, a cannula, or cones

A

T

If cone used usually spray down into the cone so this is known as semi-open but is a variant of open technique

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11
Q

With the open technique, important factors in determining the amount of cold applied to an individual lesion are the tip length, the tip material and operator technique.

A

F

Tip diameter, intermittent release of the cryogen and distance from tip to target

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12
Q

Using a B tip, a seborrhoeic keratosis requires 8-15 seconds of treatment, while a BCC requires 60-120 seconds

A

T

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13
Q

Cones used in the (semi) open technique of cryotherapy are made of rubber, neoprene or plastic

A

T

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14
Q

The chamber technique of cryosurgery is advocated for multiple types of lesions, including seborrhoeic keratoses and BCCs

A

F
Malignancies only since lower temps achieved faster
a metal chamber put over the lesion and sprayed into

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15
Q

The closed technique of cryotherapy uses probes to deliver the liquid nitrogen from the unit via a conduit line that maintains a closed system

A

T

cold metal touches the lesion but no cryogen directly touches - teflon helps reduce sticking to skin

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16
Q

The closed technique of cryotherapy use probes which are usually made of nickel

A

F

Copper

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17
Q

Using the closed technique, if the cryosurgeon does not have the right size of probe, it is better to use one that’s larger rather than smaller.

A

F

Smaller rather than larger. Avoids freezing healthy tissue

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18
Q

Thawing pain from cryotherapy can be reduced by using anaesthesia

A

F
does not always work
freezing pain is always responsive to anaesthesia - consider getting pt to apply topical local prior if large freeze planned

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19
Q

To improve cold penetrance of cryotherapy, excessive keratin should be removed

A

T

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20
Q

Pain is more intense during the freezing phase than the thawing

A

F

Pain is worse during thawing

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21
Q

Cotton swabs can be used effectively for cryosurgery

A

F

This method is obsolete. They don’t achieve optimal temperatures

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22
Q

Melanocytes are very sensitive to freezing

A

T

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23
Q

Cartilage and bone are very sensitive to freezing.

A

F

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24
Q

For cryotherapy, probes should be used in vascular lesions like haemangiomas and most vascular malformations.

A

T

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25
Q

Cryotherapy is poorly tolerated in the genital and perianal areas.

A

F

well tolerated

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26
Q

Cyrotherapy for seborrhoeic keratoses should be done in an intermittent area until the freeze halo covers the whole lesion surface and extends to a maximum of 1 or 2 mm

A

T
then it is an option to leave it or to allow a few seconds of thawing before curetting off the lesion - will bleed due to post LN2 vasodilatation so be ready with driclor

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27
Q

Cryotherapy should not be performed on solar lentigo

A

F
open spray works well on lentigines and ephilides
B or C tip, 2cm distnce for 3-5 secs single cycle
freeze halo must reach edge to avoid untreated rim
dont overtreat as risk hypopigmentation

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28
Q

Cryotherapy should not be performed on melasma

A

T

tends to hyperpigment

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29
Q

Cryotherapy can be helpful for acne lesions, scars and rhinophyma

A

T
can speed resolution of cysts and pustules
spray Rx for 5-7s and cover with topical antibiotic
good for pregnancy when few treatments appropriate
For rhinophyma can use a C tip to spray Rx after electrodessication of excess tissue. Avoid overtreating

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30
Q

Cryosurgery is an effective and safe regimen in hypertrophic scars and keloids ONLY if used in combination with other treatment

A

F

Can be used as monotherapy or with other treatments

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31
Q

In large keloids, post-surgical cryotherapy with or without ILCS can be performed in order to reduce recurrence

A

T

freezing before injecting ILCS is also useful (without surgery) can be repeated weekly

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32
Q

Venous lakes should be treated using a pre-frozen probe of the same size as the lesion, applied with pressure to empty the content for 4-5 seconds

A

T
oral mucocele can be treated in the same way - dont let the frozen mucosa touch other areas of the mouth unil it has completely thawed
digital myxoid cyst treated in same way after draining

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33
Q

When treating superficial BCCs with cryotherapy, the freeze halo should advance to 2mm outside the margin of the lesion.

A

F
5mm
treat for 30-45s

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34
Q

For squamous tumours, a 5-10mm spread beyond the tumour margin and two freezing cycles should be performed

A

T

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35
Q

Cryosurgery is an excellent treatment for KS

A

T
use if failed conventional Rx or these are contraindicated
open spray DTFC or single closed probe technique

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36
Q

Since vascular lesions are extremely sensitive to cold, cryosurgery is an excellent option for Kaposi’s sarcoma

A

T

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37
Q

Only Mohs surgery has shown better results than cryosurgery for lentigo maligna.

A

T!

good for large LM in older or inoperabe pts

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38
Q

Cryosurgery for lentigo maligna should be performed with a double freeze-thaw cycle with a 5mm margin.

A

F
1cm margin
can combine with immiquimod = ‘immunocryosurgery’

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39
Q

Segmental cryosurgery involves reducing the size by treating the centre of a lesion first, allow it to heal, and then later treating the remaining area, which is now smaller than the original.

A

F

This is true for fractional cryosurgery

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40
Q

Fractional cryosurgery consists of dividing the tumour in an imaginary grid and treating one area at a time either at the same or in different treatment sessions.

A

F

This is true for segmental cryosurgery

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41
Q

Erythema can be immediate or appear up to 30mins after cryotherapy.

A

T

discomfort/pain also occurs rapidly

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42
Q

Oedema of an area treated with cryotherapy typically occurs within a few minutes.

A

F

Mins to hours after Rx.

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43
Q

Post-cryosurgery oedema is related to pain

A

F

44
Q

Bulla formation is usually present between 1-3 days after cryosurgery

A

T

exudate can last 10-15 days - crusting (mummification) and healing occur when the exudate subsides

45
Q

On the legs, healing after cryotherapy can be as long as 2-3 months

A

T

1-2 months more typical

46
Q

Pseudoepitheliomatous hyperplasia after deep cryotherapy generally does not resolve

A

F

Disappears spontaneously after few months

47
Q

Nitrogen gas insufflation can occur if the open technique is used on a previously drained cyst

A

T

48
Q

Tendon rupture is a potential permanent complication of cryosurgery

A

T

49
Q

An expected ‘pitfall’ after cryotherapy is eschar formation

A

T

50
Q

As thawing occurs ice crystals reorganise inside the cell into larger crystals which cause further cell damage

A

T

51
Q

All cells must be destroyed during cryo treatment for successful result

A

F

cells at the periphery often damaged but not destroyed - they will later undergo apoptosis due to the damage sustained

52
Q

Isotherms are successive layers of reducing temperature eminating out from the frozen centre of the treated area

A

T

53
Q

Axial isotherms radiate deep to the frozen tissue, radial isotherms radiate laterally from the frozen tissue

A

T

54
Q

The temperature at the periphery of the ice ball is cooler than the temp at the deepest part of the ice ball in the same isotherm

A

F
temperature the same in the same isotherms whether axial or radial so temp always the same at the same distance from the centre

55
Q

Keratin is a good conductor of cryogen

A

F

very keratinized lesions hard to freeze effectively

56
Q

Ice is a good conductor of cryogen

A

T
This is part of the reason repeated freezing and longer freezing is much more effective - when ice is present further freezing is more efficient

57
Q

water is a better cryogen conductor than air

A

T

wetting a lesion assists in freezing

58
Q

Metal is the best cold conductant

A

T

applying a frozen metal probe or the tip of the cryo gun directly is very effective (closed technique)

59
Q

Air is a good conductor of cryogen

A

F

if you hold the cryo tip further away from the skin there is a rapid dimishing in effectiveness

60
Q

An office Liquid Nitrogen generator machine can produce 10L of LN per day

A

F

1-5 L

61
Q

The temp at the surface can be measured using the CRY-AC tracker cam infrared senser

A

T

can also record video and audio

62
Q

techniques to prevent a frozen metal probe sticking to the skin include
freezing probe before touching to skin
having teflon surface on probe
covering the probe with the finger of a glove
using warm water to facilitate detachment

A

T

never use force to pull of a frozen probe stuck to the skin

63
Q

tweezer technique is ideal for skin tags but required anaesthsia

A

F
ideal and no anaesthetic needed
allow freezing front to extend just to base of lesion
can leave lesion to drop of or snip off frozen tag

64
Q

The intralesional technique invovles inserting large cannulae through the centre of the lesion than spraying LN into these to freeze from the inside

A

T

ideal for keloids and for palliative treatment of large deeply seated tumours

65
Q

You should never freeze a lesion of uncertain diagnosis

A

T

66
Q

It is wise to keep a photographic record of the clinical and dermoscopic appearance of the lesions to be treated by cryosurgery

A

T

rarely done in practice if only AKs

67
Q

white skin is more sensitive to cold

A

T

pale skin types get more pain

68
Q

skin types 4-6 are prone to hyperpigmentation

A

T
skin type III also can
test patch in hidden area recomended for 3-6 types

69
Q

If freezing child dont let them eat for 1 hr before cryo

A

F
3 hrs
in case they vomit

70
Q

if freezing a baby should let them feed imediately after procedure

A

T

acts as analgesic

71
Q

Metal devices are used to protect vital structures such as the eyes

A

F
metal conducts
should use wood or plastic as poor conductors

72
Q

probes are useful for flat surface lesions but spray better for irregular surface

A

T

a probe on an irregular surface will cause very non-uniform frezing

73
Q

Blood prevents effective freezing

A

F

blood rapidly increases temp but obscures view of the treatment field. Should always work in bloodless field

74
Q

TCA is a good haemostatic agent to use prior to cryo

A

F
causes a white frost which can be confused with frozen tissue
best avoid TCA

75
Q

when treating warts it helps to
Par excess keratin
soak for 15mins in water
use semi open technique and allow the freeze front to progress just a few mm outside the lesion area

A

T

single freeze with B or C tip with cone

76
Q

If treating multiple warts consider topical anaesthesia to reduce pain

A

T

esp for genital warts

77
Q

be sure to exclude SCC in HIV pts with anogenital warts prior to freezing

A

T

must biopsy

78
Q

Molluscum can be terated with the open, semi-open or closed techniques

A

T

dont allow the freeze margin to progress beyond the edge fo the lesion

79
Q

If oral treatment failed or contraindicated can treat cutaneous larva migrans with cryo

A

T

closed technqie recomended apply a frozen 3mm probe to each end of the trail for 5-7 secs

80
Q

Infantile haemangiomas can be treated with cryotherapy

A

T
treat early to prevent growth
use closed technique with a frozen probe pressed firmly over the whole lesion for 10-20s allowing the freeze margin to extend 1-2 mm beyond the lesion only
firm pressure empties the blood
mixed IH can be treated w/ combined LN2 and ILCS
do not use LN2 on deep IH

81
Q

Pyogenic granuloma can be treated with open, closed or tweezer cryo techniques

A

T

depends on specifics of lesion

82
Q

Nodules and hypertrophic areas within port wine stains can be effectively treated with chamber cryo

A

False
good Rx but not with chamber
use tweezers for for exophytic areas or frozen door-knob probe to roll over hypertrophic areas

83
Q

Lymphangiomas can be treated with a probe applied with pressure in the same way as vascular lesions

A

T

84
Q

Lymphangiomas tend to be the clinical expression of larger underlying tumours

A

T

85
Q

Large vascular malformations can be treated with LN2 in combination with other techniques

A

T

86
Q

sebaceous hyperplasia can be treated with cryo contact probes

A

T

this is recommended technique

87
Q

Cryobiopsy means freezing a lesion to facilitate pain relief for shave biopsy rather than using LA

A

T

can use spray (open) or tweezer method e.g. for keratinhorns or pedunculated lesions

88
Q

Cryobiopsy distorts the tissue making histopath harder

A

False

histo unaffected

89
Q

Most BCCs are less than 1mm thick and have a surface diameter to depth ratio of 4:1

A

False
usually under 1mm
ratio is 6:1 mm

90
Q

spray cryo forms an ice ball with a surface diameter to depth ratio of 4:1.5 mm

A

True

probe cryo results in 4:2 mm ratio

91
Q

A 22 Mhz High frequency ultrasound (HFUS) can be used to assess tumour depth prior to LN2 to assess suitability and most appropriate technique

A

T

92
Q

Nodular BCCs can be curetted prior to LN2 by open, closed or chamber techniques

A

T
good for mixed nodular and SF esp if palliative
2 cycles recommended for nod BCCs

93
Q

when treating lesions on the ear lobe, the cartilage becoming taught indicates sufficient freezing

A

T

94
Q

Palliative Rx of cancers with LN2 should be considered;
When the skin tumor does not respond to conventional treatment (chemotherapy, radiotherapy, or surgical treatment)
When the secondary effects of the usual treatments are no longer tolerated by the patient
When underlying medical conditions (such as anemia, coagulopathies, heart conditions, diabetes mellitus, and old age) increase the risks of conventional treatments
When the proposed surgical procedure to reduce or remove the tumor is so disfiguring that the patient rejects it
In metastasis of skin tumors or internal tumors

A

T

95
Q

Palliative cryo can relieve pain, bleeding and prevent foul smell and local infection

A

T

96
Q

to treat tumours with the chamber technique the chamber must fit exactly over the tumour

A

T

ideal for thick, well demarcated tumours

97
Q

pre de-bulking with shave, curette or electrodessication prior to palliative cryo is ideal

A

T

but not always possible

98
Q

when treating tumours by palliative spray cryo keep the spray at a central point and allow the freeze edge to advance outward

A

T
but cannot do this if tumour large as central destruction would be too deep
can rpt every 2 weeks until pain and bleeding improved

99
Q

when treating tumours by palliative spray cryo overtreatment is more of a risk than under treatment

A

F

other way around

100
Q

large tumours should be treated by fractional or segmental cryo

A

T

101
Q

closed cryo on the head and neck heals in 7-10 days

A

T

102
Q

closed cryo on the arms and trunk heals in 1-2 weeks

A

F
2-3 weeks
>3 weeks on dorsa of hands

103
Q

whiter skin tends to hyperpigment, darker skin tends to hypopigment after cryo

A

F

other way around

104
Q

The reappearance of local pain several days or weeks after cryosurgery may suggest secondary bacterial infection

A

T
infection is rare
may occur after deep freeze esp if infection control measures not used

105
Q

NSAIDS are helpful for the pain of cryo

A

F

Proc Derm 2020 (50 decks)

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