Hypothermia and cold injuries are medical conditions that can result from exposure to cold temperatures or freezing conditions. There are three main types discussed: 1. Hypothermia is defined as a core body temperature below 35°C and can be mild (32-35°C), moderate (28-32°C), or severe (<28°C) with increasing risks of cardiac dysrhythmias and arrest. Rewarming methods include passive rewarming for mild cases or active external and internal rewarming for more severe hypothermia. 2. Frostbite causes freezing of the skin and deeper tissues, classified into 4 degrees of injury ranging from superficial frostnip to deep tissue freezing and

1. HYPOTHERMIA
& COLD INJURIES
Farooq Khan MDCM
PGY-5 FRCP-EM
February 28th 2014

2. Background
• Definition: Core Temp <35°C
• Severity:
– Mild hypothermia: 32-35°C
• Shivering thermogenesis, amnesia, dysarthria
– Moderate hypothermia: 28-32°C
• Stupor, extinguished shivering, dysrhythmias
– Severe hypothermia: <28°C
• V-fib risk, acid base disturbance, decreased CO and CBF

3. DDx
• Accidental
(environmental) exposure
• Metabolic disorders
– Hypoglycemia
– Hypothyroidism
– Hypoadrenalism
– Hypopituitarism
• Hypothalamic and CNS
– Head trauma
– Tumor
– Stroke
– Wernicke encephalopathy
• Drugs
– Ethanol
– Sedatives-hypnotics
• Sepsis
• Dermal disease
– Burns
– Exfoliative dermatitis
• Acute incapacitating
illness
• Massive fluid or blood
resuscitation
• Malnutrition

4. ECG
• Typical sequence is sinus brady > a fib w/ slow
ventricular response > v-fib > asystole
• Other ECG findings:
– Osborn (J) wave
– T-wave inversions
– PR, QRS, QT prolongation
– Muscle tremor artifact
– AV block
– PVCs

5. Typical ECG
Image courtesy of:

7. Supportive measures
• Handle pt gently
– V-fib may be induced by rough handling of pt due to
irritable myocardium (anecdotal)
• O2
– Hypothermia causes leftward shift of oxyhemoglobin
dissociation curve
• IVF
– Hypothermia > impaired renal concentrating ability >
cold diuresis
– Pts are prone to rhabdo
– Intravascular volume is lost due to extravascular shift

8. Specific therapies
• Abx
– Give if suspect sepsis (e.g. hypothermia fails to correct w/
rewarming measures)
• Thiamine
– Consider if Wernicke disease is possible cause of
hypothermia (e.g. alcoholic pt)
• Hydrocortisone
– Consider if pt has history of adrenal suppression or
insufficiency
• Thyroxine
– Consider if any suspicion for hypothyroidism/myxedema
coma

9. Passive Rewarming
• Consider in pt w/ mild hypothermia (>32°C)
who is able to generate intrinsic heat
• Techniques
– Removal from cold environment
– Remove wet clothing
– Insulation with blankets

10. Active rewarming
• Indications
– Cardiovascular instability
– Moderate to severe hypothermia (<32°C)
– Inadequate rate or failure to rewarm
– Endocrine insufficiency
– Traumatic or toxicologic peripheral vasodilation
– Secondary hypothermia impairing thermoregulation
• Rewarm trunk BEFORE the extremities
– Otherwise may lead to hypotension ("core temperature
afterdrop")
• Warmed vasodilated peripheral tissue allows cooler blood in
extremities to circulate back to core

11. Active External Rewarming
• Consider in:
– Moderate-severe
hypothermia
– Mild hypothermia in pt
who is unstable or
cannot generate
intrinsic heat
– Failure to respond to
passive external
rewarming
– May be ineffective in
pts w/ poor perfusion
or in cardiac arrest
• Techniques
– Warm IV bags applied
to skin
– Heating blankets
– Radiant heat
– Forced air - Bair hugger

12. Active Internal Rewarming
• Consider alone or
along with active
external warming in:
– Cardiovascular
instability / life-
threatening
dysrhythmias
– Severe hypothermia
– Moderate
hypothermia which
fails to respond to less
aggressive measures
• Techniques
– Warm humidified O2
– Heated IV fluids: 40-42°C
• Level 1 infuser
• Microwave on high x 2min
– Peritoneal lavage
• Encourages liver function
– Pleural lavage
• 2 large chest tubes
– GI tract lavage and
bladder lavage
• Limited area for heat exchange
and can cause Electrolyte shifts
– Bypass/ECMO/AV
Dialysis

13. ACLS
• CPR
– Only perform if pt truly does not have a pulse
(unnecessary CPR may lead to V-fib)
– Spend 30-45s attempting to detect respiratory
activity and pulse before starting CPR
• Pt not dead until warm and dead: 30-32°C
• Active internal rewarming indicated for
cardiac arrest
– Mediastinal and direct cardiac lavage

14. ACLS
• Dysrhythmias (Occur <30°C)
– Active rewarming is treatment of choice
• Most dysrhythmias (e.g. sinus brady, a-fib/flutter) require no
other therapy
• Activity of antiarrhythmics is unpredictable in hypothermia
• Hypothermic heart is relatively resistant to atropine, pacing,
and countershock
– V-fib
• May be refractory to therapy until pt is rewarmed
• Attempt a single defibrillation attempt
– If unsuccessful continue CPR and attempt defibrillation again
once temp >30C (86F)
– IV medications: increase interval between doses

15. FREEZING INJURIES

16. Background
• Results from the freezing of tissue
• It is a disease of morbidity, not mortality
• Risk correlated with temperature and wind speed
– Risk is <5% when ambient temperature (includes wind
chill) is > –15°C
– Most often occurs at ambient temp < –20°C
• Can develop w/in 2-3sec when metal surfaces
that are at or below –15°C are touched
• Most commonly affects distal part of extremities,
face, nose, and ears

17. Pathophysiology
• Freezing alone is usually not sufficient to
cause tissue death
– Thawing contributes markedly to the degree of
injury
– Endothelial damage, beginning at the point of
thaw, is the critical event in frostbite
• Resulting damage results in swelling, platelet
aggregation, vessel thrombosis

18. Zones of Injury
• Zone of Coagulation
• Most severe and usually most distal
• Damage is irreversible
• Zone of Hyperemia
• Least severe and usually most proximal
• Generally recovers w/o treatment in <10d
• Zone of Stasis
• Middle zone characterized by severe, but possibly
reversible, cell damage
• It is this zone for which treatment may have benefit

19. Classification
• First degree (frostnip)
– Partial-skin freezing
– Stinging and burning, followed by throbbing
– Numbness, erythema, swelling, dysesthesia,
desquamation (days later)
– Prognosis excellent

20. Classification
• Second degree
– Full-thickness skin freezing
– Numbness followed by aching and throbbing
– Skin blisters form w/in 6-24hr
• Desquamate and form hard black eschars over several
days
– Prognosis is good

21. Classification
• Third degree
– Damage extends into subdermal plexus
– Extremity feels like a "block of wood" followed by
burning, throbbing, shooting pains
– Hemorrhagic blisters form and are a/w skin
necrosis and blue-gray discoloration
– Prognosis is often poor
– Tissue loss involving entire thickness of skin

22. Classification
• Fourth degree
– Extension into subcutaneous tissues, muscle,
bone, and tendon; little edema
– Deep, aching joint pain
– Skin is mottled w/ nonblanching cyanosis and
formation of deep, dry, black eschar
– Prognosis is extremely poor

23. Pre-thaw
• Assess Doppler pulse and appearance
• Protect part – no friction massage
• Stabilize core temperature
• Address medical and surgical conditions
• Rehydrate patient
• Prevent partial thaw and refreeze
– Refreezing will cause even more severe damage

24. Thaw
• Analgesia
– Provide parenteral opiates
• Blocking prostaglandin, thromboxane, and arachidonic
cascade
• Ibuprofen 400mg po q8h
• Rapid rewarming is the core of therapy and should be
initiated as soon as possible
– Extremities
• Place in water w/ temperature of 37- 40°C (do not exceed 42°C)
• Leave in for 20-30min, when the extremity should become pliable
and erythematous
– Face
• Apply moistened compresses soaked in warm water

25. Post-thaw
• Tetanus prophylaxis
• Local wound care
– Apply topical aloe vera cream q6hr (interrupts
arachidonic acid cascade)
– Affected digits should be separated w/ cotton and
wrapped w/ sterile, dry gauze
– Dry, elevate and splint
– Blister removal is controversial
• Consider drainage of nonhemorrhagic bullae that interfere
w/ movement
• Never debride hemorrhagic bullae

26. Post-thaw
• Systemic care
– Hydrotherapy at 37°C tid
– Streptococcal prophylactic Pen G 500kU IV q6hr
– Intra-arterial tPA reduces digit amputation rate
– Phenoxybenzamine to reduce vasospasm
• Surgery
– Monitor compartment pressures
– Amputation
• May be required if wet gangrene or infection occurs
• Usually not performed until full demarcation occurs (3-4 wk)

27. Sequelae
• Acute
– Rhabdomyolysis, ATN, Electrolyte fluxes
– Core temperature afterdrop
– Compartment syndrome
• Chronic
– Neuropathic pain/dysesthesias, thermal sensitivity
– Autonomic dysfunction (Hyperhidrosis, Raynaud’s)
– MSK (atrophy, tenosynovitis, strictures, OA)
– Derm (edema, ulcers, delayed cancers)

28. NON-FREEZING INJURIES

29. Pernio (Chillblains)
• Background
• Mild but uncomfortable inflammatory lesions
of skin
– Caused by long-term intermittent exposure to
damp, nonfreezing ambient temperatures

30. Pernio
• Symptoms
– Tingling, numbness, pruritus,
burning paresthesias
– Cutaneous manifestations
appear up to 12hr after acute
exposure:
– Localized edema, erythema,
cyanosis, plaques, nodules
• May progress in rare cases to
ulcerations, vesicles, and bullae
– Rewarming may result in
formation of tender blue
nodules which may persist for
days
• Treatment
• Affected skin should be
rewarmed, gently bandaged,
and elevated
• Nifedipine 20mg PO TID may be
helpful as both prophylactic and
therapeutic tx
• Topical corticosteroids and oral
steroid burst have been shown
to be useful

31. Cold Panniculitis
• Prolonged exposure to temp >freezing leads to
mild necrosis of subcutaneous fat tissue
• Seen in children (popsicles) and women
involved in equestrian activities
• Resolution may result in adipose fibrosis w/
cosmetic defects
– There is no treatment

32. Trench Foot (Immersion Foot)
• Background
• Develops slowly over hours-days when foot is
exposed to cold/wet conditions
• Reversible injury may progress to irreversible
injury

33. Trench Foot
• Clinical Features
– Tingling/numbness is initial symptom
– Foot appears pale, mottled, anesthetic, pulseless, and immobile
• Initially does not change after rewarming
– Hyperemic phase begins w/in hr after rewarming
• Assoc w/ severe burning pain and reappearance of proximal sensation
– As perfusion returns to foot over 2-3d edema and possibly
bullae may form
– Anesthesia persists for weeks and may be permanent; gangrene
may occur
• Treatment
– Keep feet clean, warm, dryly bandaged, elevated
– Monitor for signs of infection

34. Sources
• Tintinalli
• Rosen
• WikEM: Jordan Swartz, Manpreet Singh, Ross
Donaldson