234 SECTION 3 • MEDICAL PROBLEMS IN THE ATHLETE
EPIDEMIOLOGY
- Frostbite is most common in active individuals from
30–49 years of age. High-risk outdoor activities in
inclement environments account for a large percent-
age of injuries. - Risk factors for frostbite are shown in Table 39-2.
Ethanol and psychiatric problems underlie up to 70%
of most cases of frostbite. The need for amputation
correlates with the duration of cold exposure rather
than the lownessof the temperature. This explains
why the impaired judgement resulting from ethanol
use and psychiatric illness account for such a large
percentage of injuries (Reamy, 1998). - Anatomic sites of injury are in order: feet and hands
(90% of all frostbite), ears, nose, cheeks, and the penis
(a particular concern for runners).
PATHOPHYSIOLOGY
- There are three synchronous pathways that lead to
tissue damage in frostbite: tissue freezing, hypoxia,
and the release of inflammatory mediators. Each
pathway multiplies and catalyses the damage caused
by the other pathways. Freezing leads to denaturation
of the membrane lipid-protein matrix and cellular dis-
ruption. Hypoxia occurs from cold-induced vasocon-
striction that triggers acidosis, increased viscosity,
microthrombosis, and vessel endothelial damage.
Inflammatory mediators, (PGF2a, Thromboxane A2)
are released from damaged endothelium which triggers
more vasoconstriction, platelet aggregation, thrombo-
sis, hypoxia, and cell death. The same prostaglandins
are found in the blister fluid of heat and frostbite dam-
aged skin (Reamy, 1998). - The release of these prostaglandins peaks during
rewarming,therefore cycles of recurrent freezing and
rewarming must be avoided to lessen the extent of
injury(level of evidence B, nonrandomized clinical
trials and systematic review) (Heggers et al, 1987;
McCauley et al, 1983).CLINICAL FEATURES- Symptoms include numbness, clumsiness, tingling,
and throbbing pain after rewarming. - The signs of frostbite were classically divided into first
through fourth degrees. This scheme is not prognosti-
cally useful. It is better to distinguish between two
types of injury: superficial and deep frostbite.
Superficial injury is characterized by normal skin color,
large blisters filled with clear or milky fluid, intact pin-
prick sensation, and skin that will indent with pressure.
Deep frostbite shows small blood-filled dark blisters,
nonblanching cyanosis, skin that is wooden to the touch
and will not indent with pressure.
DIAGNOSIS•Tissue viability is not ultimately determined until 22–45
days post injury. The primary utility of diagnostic tests
is to help define tissue viability at an earlier time.- Doppler flow studies and angiography can determine
tissue viability and predict the need for surgical inter-
vention as early as 7 days postinjury. Technitium 99 m
scintigraphy can be employed as soon as 72 h from
injury to assess tissue viability with a positive predic-
tive value(ppv) of 0.84. A scan on day 7 raises the
ppv to 0.92 (level of evidence A, randomized clinical
trial). (Cauchy et al, 2000) - Magnetic resonance imaging/magnetic resonance
angiography(MRI/MRA) may emerge as the optimal
modality for early tissue assessment.
TREATMENT- Field warming should not be instituted until refreez-
ing can be prevented. The injured part should be pro-
tected with a loose bulky splint during transport for
definitive care. Hypothermia should be treated, and
smoking, ethanol, and massage of the frozen part
should be avoided. - Definitive emergency department care is outlined in
Table 39-3. It is based on the work of Heggars and
McCauley (Murphy et al, 2000). Adjuvant therapies
with heparin, warfarin, steroids, dextran, vitamin C,
and hyperbaric oxygen have not been proven to be
helpful. Studies using TPA are still preliminary.
Pentoxifylline (Trental) has been shown to be useful
in pedal frostbite (Hayes et al, 2000).
TABLE 39–2 Risk Factors for Frostbite
PREDISPOSING FACTORS
BEHAVIORAL ORGANIC
Ethanol use Prior cold injury
Psychiatric illness Wound infection
Motor vehicle problems Atherosclerosis
Homelessness Diabetes mellitus
Smoking Fatigue
Improper Clothing
High-risk outdoor activities (back-country
skiing/mountaineering)