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HYPOTHERMIA& COLD INJURIES
Farooq Khan MDCMPGY-5 FRCP-EM
February 28th 2014
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
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
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
Typical ECG
Image courtesy of:
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
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
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
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
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
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
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
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
FREEZING INJURIES
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
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
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
Classification
• First degree (frostnip)– Partial-skin freezing– Stinging and burning, followed by throbbing– Numbness, erythema, swelling, dysesthesia,
desquamation (days later)– Prognosis excellent
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
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
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
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
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
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
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)
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)
NON-FREEZING INJURIES
Pernio (Chillblains)
• Background• Mild but uncomfortable inflammatory lesions
of skin– Caused by long-term intermittent exposure to
damp, nonfreezing ambient temperatures
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
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
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
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
Sources
• Tintinalli• Rosen• WikEM: Jordan Swartz, Manpreet Singh,
Ross Donaldson