Medical use for liquid nitrogen
Dermatologists have used cryotherapy since the turn of the
century. After the development of the vacuum flask to store
subzero liquid elements, such as nitrogen, oxygen, and hydrogen,
the use of cryotherapy dramatically increased. By the 1940s,
liquid nitrogen became available and the most common method of
application was by means of a cotton applicator. In 1961, Cooper
introduced a closed-system apparatus to spray liquid nitrogen.
By 1990, almost all dermatologists used liquid nitrogen in their
cryotherapy practice.
The general advantages of liquid nitrogen therapy are its ease
of use, its low cost, and its good cosmetic results. Most skin
cancers are treated with excision or other destructive
procedures, such as electrodessication and curettage.
Superficial basal cell skin cancers and Bowen disease can be
treated with liquid nitrogen.
When using the spray technique, the liquid nitrogen is applied
directly on the skin, and evaporation (boiling heat transfer)
occurs in which the heat in the skin is quickly transferred to
the liquid nitrogen. This process results in the liquid nitrogen
evaporating (boiling) almost immediately. Liquid nitrogen is the
best and universal freezing source because of its low boiling
point and its ease of use. Other sources that are used to
freeze, such as Freon, carbon dioxide, and nitrous oxide, do
exist, but they are not as efficient in destroying lesions.
Various lesions have been treated with liquid nitrogen. Because
of the histological differences in lesions, different
freeze-thaw cycles are used to successfully destroy them. For
most of these lesions, cryotherapy is not the only and often not
the best modality for treatment. However, it does represent a
valuable alternative for selected patients. For some lesions,
such as actinic keratoses, warts, and seborrheic keratoses,
cryotherapy is the standard first-line therapy.
Although very effective, liquid nitrogen therapy may lead to
complications and it is not indicated in some cases. Acute
complications include headache, pain, and blister formation.
Delayed complications include hemorrhage, infection, excessive
granulation tissue formation. Relative contraindications include
cold intolerance, cold urticaria, cryoglobulinemia and Raynaud
disease. Cryotherapy is contraindicated when used near the eye
margins.