Cryotherapy Overview and Mechanisms

Study Notes

Cryosurgery involves localized freezing to destruct or remove living tissues safely and effectively.
It is cost-effective, reproducible, repeatable, and a straightforward office procedure with excellent healing and cosmetic outcomes.

Liquid nitrogen is the preferred cryogen for dermatological applications, especially for malignant skin lesions.
Other cryogens and their freezing points:
- Liquid nitrogen: -196°C
- Liquid oxygen: -183°C
- Nitrous oxide: -89°C
- Solidified CO2: -78°C
- Dimethyl ether: -24°C

Direct Tissue Injury: Involves heat transfer, inflammation, and direct cellular damage.
Indirect Tissue Injury: Results from vascular stasis and subsequent tissue hypoxia.
Ice Formation and Cellular Injury: Rapid heat transfer during cryogen application leads to ice formation, damaging cell membranes and organelles.
Osmolarity Changes: Increased solute concentration from extracellular ice formation disrupts cell membranes.
Thermal Shock & Denaturation: Rapid freezing followed by slow thawing enhances tissue destruction.
Vascular Changes: Ischemic necrosis occurs due to microthrombi, leading to tissue destruction.
Cryoimmunomodulation: Low temperatures may enhance immune response against viral/tumor cells.

Viral Lesions: Warts, molluscum contagiosum, condyloma acuminata.
Benign Lesions: Cystic acne, acne scars, keloids, skin tags, seborrheic keratosis, and others.
Premalignant Lesions: Actinic keratoses, leukoplakia, Bowen's disease.
Malignant Lesions: Basal cell carcinoma, squamous cell carcinoma, lentigo maligna melanoma.
Not suitable for large tumors (>2 cm), recurrent lesions, or anatomical locations like feet or lower legs.

Absolute Contraindications: Blood dyscrasias, cold urticaria, areas with compromised circulation, significant sensitivity to cryotherapy.
Relative Contraindications: Keloidal tendencies, autoimmune diseases, ongoing immunosuppressive treatment, and more.

Dipstick Technique: Simple but less effective; cotton tip applicator in liquid nitrogen applied to lesion.
Spray Technique: Most popular; liquid nitrogen sprayed on lesions using varying methods for desired coverage.
Cone Spray Technique: Concentrates cryogen to minimize lateral spread; higher tissue destruction rate.
Intralesional Cryotherapy: Delivers cryogen through a needle directly into deeper scars or lesions, preserving the epidermis.
Forceps/Clamp Technique: For small skin tags, using a hemostat dipped in liquid nitrogen.

Effective freeze times vary by condition; for example:
- Common warts: 10-15 seconds
- Keloids: 20-30 seconds
- For tumors, at least two freeze-thaw cycles of 30 seconds with a 5-minute thaw period are required.

Initially, a white ice field forms, followed by a violet halo and hemorrhagic blister which eventually forms an eschar.
Frozen area contracts within 10-14 days; follow-up is needed to assess healing and manage potential complications.

Immediate Complications: Edema, blister formation, pain, bleeding, and vasovagal responses.
Delayed Complications: Hemorrhagic blisters, wound infections, delayed healing, and rare hypertrophic scarring.