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NON-FREEZING COLD INJURY
Non-freezing cold injuries or NFCI occur when
tissue fluids do not freeze (which usually at
about -0.5C), but local temperatures remain
low for several hours or days. It is likely to
be much more common than currently believed,
because it often goes unreported and is often
under-diagnosed.
The affected individual has usually been cold
and wet for a sustained period, often having
been unable to dry out satisfactorily. On
rewarming, it becomes apparent that the limb(s)
(most commonly the lower legs) has developed a
localised alteration in sensation. On
rewarming there is a short period of paleness
followed redness with swelling and pain. This
pain is much more prolonged than the rewarming
pain normally experienced in freezing cold
injury, and is the most common reason for
presentation. The last phase can last up to
many months after initial injury, during which
time persisting long term sequelae may become
apparent. After the initial NFCI there is an
increased sensitivity to cold.
There are often surprisingly few clinical
signs for the doctor or medic to find.
Infrared thermography is used by the UK
military to assess an individual’s response to
a standardised cold stress, and this test may
be helpful in confirming the diagnosis,
assessing the severity of the injury, and
finally monitoring the recovery or otherwise
from the NFCI. There appears to be a
significant variability in the response of
some individuals to current infra-red
thermography test.
NFCI vary in severity from mild to severe. In
severe cases the cold sensitisation is so
serious that individuals are unable to work
outside. There is often persisting oedema and
hyperhidrosis making the individual
susceptible to fungal infections. Chronic pain
resembling causalgia or reflex sympathetic
dystrophy is reported. The profound sensory
neuropathic foot can develop ulceration and
tissue loss, ultimately resulting in either
minor or major lower limb amputation. Ongoing
care within a specialist foot clinic using
custom made shoes and insoles appear to
improve functional outcome. Multidisciplinary
team approaches such as healing of the
ulcerated neuropathic foot using patella
bearing orthoses has been described. NFCI pain
is often so severe as to require tricyclic
antidepressants, and this should be instituted
at an early stage. Failure to do so increases
the risk of developing severe chronic pain
resistant to all subsequent treatment
modalities. Early involvement of pain
specialists is important. Sympathectomy
usually results in longer term deterioration.
It is thus essential to control pain following
NFCI at the earliest opportunity.
Unlike freezing cold injury, NFCI should be
allowed to rewarm slowly. It is possible that
hyperbaric oxygen may have value in early
treatment too, although no trials appear to
have assessed that use. Gross tissue damage
following NFCI is relatively rare in peacetime
experience, and after initial slow rewarming,
management should follow the standard
conservative protocol employed in freezing
injury.
With the likelihood of chronic sequelae and
only limited potential for treatment, the most
effective approach to NFCI is to try to
prevent its occurrence. There is a need to
raise awareness to those most susceptible,
particularly junior military recruits, for
example. Ultra-early recognition of NFCI, even
in the field, might be possible by the
introduction of a simple field scoring system
(not dissimilar to the Lake Louise Scoring
System currently used for field assessment of
acute mountain sickness). Although almost all
cases of NFCI involve the feet, as many as 25%
may also have injured hands. Afro-Caribbeans
appear to have a significantly increased
susceptibility to NFCI as well as freezing
cold injury. This may be a result of an
impaired or reduced cold induced vasodilatory
response in Afro-Caribbeans as compared to
Caucasians. These ethnic differences remain
when Afro-Caribbeans move to colder areas.
http://www2.armynet.mod.uk/armysafety/features/nfci.htm
http://www.expeditionmedicine.co.uk/resource.php?id=59
C Imray, A Grieve, S Dhillon, the Caudwell
Xtreme Everest Research Group. Cold damage to
the extremities: frostbite and non-freezing
cold injuries.
Postgraduate Medical Journal 2009; 85:481-488.
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