FROSTBITE
By Dr. Clare O'Leary and Pat Falvey.

Frostbite occurs at temperatures below 0°c in dry cold conditions, especially if there is wind or the tissues are wet.

CLASSIFICATION OF FROSTBITE

• First degree - Superficial frostbite with redness and swelling
• Second degree - Blebs or vesicles in addition
• Third degree - Deep frostbite; the tissues become grey, dark blue
--or black
 
SUPERFICIAL FROSTBITE - CLINICAL FEATURES

• Affects the skin and subcutaneous tissues
• Skin becomes white and frozen
• On rewarming, the skin becomes mottled and blue/purple
• Paraesthesias (abnormal sensations) are common
• Within 24-48hrs, blebs filled with clear fluid appear
• Black carapace (shell) forms (insensitive)
• Gangrene (tissue death) is superficial (a few mm)
• After weeks, the carapace peels off
• The underlying tissue is pink, very sensitive and there may be
--abnormal sweating
• It takes on a normal appearance in 2-3months
 
DEEP FROSTBITE - CLINICAL FEATURES

• Involves the deeper structures (muscles, bones and tendons)
• The part is insensitive, wooden and grey-purple or white marble in --colour
• Blisters filled with dark purple fluid appear after some weeks
• Eventually dry gangrene and mummification occur
• A cast of the tissue separates
• Permanent loss of tissue is almost inevitable
• The limbs may return to normal over months
• Amputation should never be carried out early on
• A deep boring pain may be present
 
FACTORS PREDISPOSING TO FROSTBITE

• Environment
• Wind Chill
• Duration of Exposure
• Availability of Shelter
• Whether or not the part is wet
• Personal factors
• Type of clothing
• Intercurrent disease
• Low morale
• Fatigue
• Previous cold injury
• Smoking
• Altitude
• Dehydration
• Hypoxia
• Low calorie intake
 
PREVENTION OF FROSTBITE

• Stay dry
• Stay warm
• Maintain hydration
• Keep the part free from abrasion
 
TREATMENT OF FROSTBITE

• Avoid further trauma
• Avoid freeze-thaw-freeze
• Avoid infection
• Keep clean
• Rewarm
• Maintain morale
• Delay surgery
• Treat associated conditions
• Avoid subsequent frostbite
• Do NOT beat, rub or overheat
• Do NOT thaw in the field (freeze-thaw sequence)
• Protect the frozen part from trauma
• Once thawing starts, continue and avoid refreezing