Hypothermia (Severe)MANAGEMENT

ENVIRONMENTAL AND EXPOSURE PRESENTATIONS · 12 SECTIONS

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722 items

☷ Legend

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Cardiovascular Presentations71▾

Respiratory Presentations52▾

Neurological Presentations83▾

Gastrointestinal Presentations74▾

Genitourinary and Reproductive Presentations48▾

Infectious Disease Presentations148▾

Trauma Presentations89▾

Toxicologic Presentations80▾

Psychiatric Presentations26▾

Musculoskeletal and Rheumatologic Presentations96▾

Dermatology Presentations23▾

Environmental and Exposure Presentations27▾

Acute Mountain Sickness Arterial Gas Embolism Bee-Wasp Sting (Anaphylaxis)Chilblains Ciguatera Fish Poisoning Coral Cut Decompression Sickness Electrical Burn Injury Envenomation (snake, spider, insect)High Altitude Cerebral Edema (HACE)High Altitude Pulmonary Edema (HAPE)High-altitude illness Hypothermia Hypothermia (Mild)Hypothermia (Severe)Immersion Foot Lightning Strike Injury Scombroid Fish Poisoning Scorpion Envenomation Sea Urchin Injury Shark Bite Snake Envenomation Spider Bite (Black Widow)Spider Bite (Brown Recluse)Stingray Spine Injury Tick paralysis White Phosphorus Burn

Hematologic and Oncologic Presentations36▾

Pediatric-Specific Presentations19▾

Endocrine and Metabolic Presentations45▾

ENT and Maxillofacial Presentations27▾

Ophthalmologic Presentations19▾

Obstetric Presentations23▾

Systemic and Miscellaneous Presentations17▾

01Approach to the Critical Patient/attcp96

Immediate stabilization

›Scene and patient safety

›Remove from cold environment immediately

›Remove wet clothing

›Minimize patient movement — rough handling can precipitate VF

›Keep patient horizontal

›Orthostatic hypotension and afterdrop risk with upright positioning

›Avoid peripheral warming until core rewarming initiated

›Insulate with vapor barrier and dry insulating layer

›Hibler method: plastic sheeting plus sleeping bag

›Cover head — significant heat loss via scalp

›Airway and oxygenation

›Warmed humidified oxygen via mask or nasal cannula

›Assists with core rewarming

›Target SpO2 >= 94%

›If GCS warrants, proceed to definitive airway management

›RSI preferred — pre-oxygenate meticulously

›Laryngoscopy may trigger VF; have defibrillator immediately available

›Ventilate gently — lung compliance reduced and VF risk with overvigorous bag-mask

›Circulatory assessment

›Palpate pulse for up to 60 seconds before declaring pulseless

›Profound bradycardia may be undetectable clinically

›POCUS/bedside echo to confirm cardiac activity

›If VF or pulseless VT, begin CPR immediately

›Single defibrillation attempt at standard energy

›If unsuccessful, defer further shocks until core temp >= 30 degrees C (WMS) or up to 3 attempts (ERC)

›Mechanical CPR device preferred for prolonged transport

›Consistent compressions during ECLS transfer

›ACEP Level B recommendation for mechanical CPR in refractory arrest

Rewarming strategy

›Passive external rewarming

›For mild to moderate hypothermia and hemodynamically stable patients

›Remove wet clothing, dry patient, insulate

›Allow endogenous thermogenesis in patients who can shiver

›Expected rewarming rate 0.5 to 2.0 degrees C per hour

›Active external rewarming

›Forced-air warming blankets applied to trunk

›Bair Hugger or equivalent to torso, not extremities initially

›Peripheral rewarming before core risks afterdrop and vasodilation

›Chemical heat packs to axilla and groin

›Minimally invasive core rewarming

›Warmed IV normal saline at 40 to 42 degrees C

›Fluid volume resuscitation target

›Corrects cold diuresis hypovolemia

›Warmed humidified oxygen via circuit

›Adds approximately 1 to 2 degrees C per hour contribution

›Invasive core rewarming

›Bladder lavage with warmed saline

›Simple and readily available adjunct

›Lower efficacy than thoracic lavage

›Thoracic warm water lavage at 42 degrees C

›Via bilateral pleural drains

›Reserved for cardiac arrest without ECLS access

›Peritoneal lavage with warmed saline

›Rapid core rewarming option

›Useful when ECLS not immediately available

›ECLS rewarming

›Gold standard for hypothermic cardiac arrest

›ECMO preferred over cardiopulmonary bypass

›41% greater survival probability with ECMO versus CPB

›Target rewarming rate less than 5 degrees C per hour

›Faster rates associated with worse neurological outcomes

›Transfer to ECLS-capable center as soon as possible

›Contact receiving center in advance to confirm ECMO availability

›AHA 2025 guideline recommendation

Hemodynamic and monitoring targets

›Monitoring bundle

›Continuous cardiac monitoring

›VF risk highest below 28 degrees C

›Osborn J wave monitoring

›Core temperature probe

›Esophageal thermistor most accurate in intubated patient

›Epitympanic thermistor acceptable alternative

›Avoid peripheral or infrared thermometers — unreliable in severe hypothermia

›Pulse oximetry with limitations awareness

›Peripheral vasoconstriction may render readings inaccurate

›Arterial line for direct pressure monitoring

›Potassium threshold for futility

›Serum K+ >= 12 mmol/L strongly associated with non-survival

›Reflects irreversible cell lysis rather than reversible intracellular shift

›Do not use as sole criterion; assess clinical context

›Serum K+ < 12 mmol/L: resuscitation should continue

›"No one is dead until warm and dead"

›Survival with full neurological recovery reported after CPR > 6 hours

Key decision points and escalation

›Escalation triggers

›Core temp < 28 degrees C with any cardiac instability — activate ECLS transfer

›SBP < 90 mmHg or ventricular arrhythmias mandate ECLS-capable centre

›Bypass non-ECLS hospitals when feasible

›VF refractory to 1 to 3 defibrillation attempts — continue CPR, prioritize rewarming

›Antiarrhythmics have limited efficacy below 30 degrees C

›AHA 2025: no specific recommendation for or against antiarrhythmics in hypothermic arrest

›Suspected secondary cause — treat concurrently

›Myxedema: IV levothyroxine + hydrocortisone

›Sepsis: broad-spectrum antibiotics

›Consult triggers

›Cardiac surgery or ECMO team — cardiac arrest or hemodynamic instability

›Endocrinology — suspected myxedema coma or adrenal crisis

›Toxicology — ingestion or substance use suspected

›Trauma surgery — concurrent traumatic injuries

02History/hx49

Exposure and event details

›Cold exposure context

›Duration and nature of exposure

›Outdoor cold, avalanche burial, cold water submersion, indoor cold

›Estimated down time and time from discovery to rescue

›Witnessed vs. unwitnessed collapse

›Witness account of level of consciousness at scene

›Air pocket presence if avalanche burial

›Submersion history

›Duration underwater

›Water temperature

›Protected vs. unprotected submersion

Symptom progression

›Neurological trajectory

›Initial confusion or ataxia

›Shivering ceased — suggests temp < 30 degrees C

›Paradoxical undressing behavior reported

›Progression to coma

›GCS trend from witnesses

›Unresponsiveness onset timing

›Cardiorespiratory symptoms

›Chest pain or palpitations before collapse

›Dyspnea or respiratory distress

›Syncope

Risk factors and precipitants

›Predisposing conditions

›Endocrine disorders

›Hypothyroidism — myxedema coma overlap

03Physical Exam/exam55

Vitals and temperature

›Core temperature measurement

›Esophageal probe — gold standard in intubated patient

›Placed 24 cm past incisors to level of heart

›Continuous monitoring essential

›Epitympanic thermistor — acceptable when esophageal not feasible

›Tympanic membrane perfusion dependent

›Rectal probe — useful but lags core temperature by 15 to 30 minutes

›Infrared ear and oral thermometers not reliable — avoid in severe hypothermia

›Hemodynamic assessment

›Heart rate — bradycardia expected; rate < 40 per minute common below 28 degrees C

›Blood pressure — hypotension from peripheral vasodilation and myocardial depression

›Respiratory rate — bradypnea or apnea possible; count for 60 seconds

›Pulse — may require 60-second palpation to detect

Neurological examination

›Level of consciousness

›GCS scoring

›Mild: confused (GCS 13 to 14)

›Moderate: stuporous (GCS 9 to 12)

›Severe: comatose (GCS <= 8)

›AVPU scale when rapid staging needed

›Pupillary assessment

›Fixed dilated pupils NOT reliable for death determination in hypothermia

›Hypothermia causes pharmacological mydriasis

›Do not use pupils to withhold resuscitation

›Motor response and reflexes

›Muscle rigidity — can mimic rigor mortis; NOT reliable for death determination

›Shivering absent below approximately 30 degrees C

04Differential Diagnosis/ddx45

Life-threatening mimics and co-existing conditions

›Myxedema coma

›ICD-10 E03.5

›Hypothermia plus altered mental status plus bradycardia in thyroid disease patient

›Mortality 30 to 60% without treatment

›Concurrent hydrocortisone required if adrenal insufficiency possible

›Sepsis with hypothermia

›ICD-10 A41.9

›Hypothermia is an independent predictor of mortality in septic patients

›Elderly and immunocompromised patients most affected

›Concurrent infection frequently precipitates accidental hypothermia

›Adrenal crisis

›ICD-10 E27.2

›Hypotension, altered mental status, hyponatremia, hypothermia

›Hydrocortisone 100 mg IV stat required

›Can coexist with primary hypothermia

Toxicological and metabolic causes

›Drug or toxin induced hypothermia

›Opioids — sedation, vasodilation, respiratory depression

›Naloxone for suspected opioid toxidrome

›ICD-10 T40.x appropriate

›Ethanol intoxication — most common drug in accidental hypothermia

›Peripheral vasodilation with subjective warmth impairs judgment

›Phenothiazines and antipsychotics — impaired hypothalamic thermoregulation

›Hypoglycemia

›ICD-10 E16.0

›Impairs thermogenesis

›Always check glucose; treat with dextrose if confirmed

05Laboratory Tests/lt61

Critical prognostic labs

›Serum potassium

›K+ >= 12 mmol/L — marker of irreversible cell lysis and futility

›Initial hypothermia causes hypokalemia via intracellular shift

›Cardiac arrest with cell lysis causes hyperkalemia

›K+ < 12 mmol/L: resuscitation should continue regardless of arrest duration

›Serial potassium monitoring during rewarming

›K+ may rise rapidly as cells release potassium

›Target potassium normalization concurrently with rewarming

›Lactate

›Elevated lactate reflects global hypoperfusion

›Prognostic marker for outcome

›Serial trending every 1 to 2 hours during resuscitation

Metabolic panel

›Glucose

›Hypoglycemia common — glycogen stores depleted with prolonged cold exposure

›Point-of-care glucose immediately on arrival

›Treat hypoglycemia with 50 mL dextrose 50% IV or dextrose infusion

›Insulin resistance occurs in hypothermia

›Avoid overly aggressive insulin even if glucose elevated

›Electrolytes and renal function

›Cold diuresis causes hypovolemia and electrolyte losses

›Sodium, chloride, magnesium, phosphate monitoring

›Renal function baseline for medication dosing

›BUN and creatinine for rhabdomyolysis-associated AKI risk

Haematological and coagulation

›Complete blood count

›Hemoconcentration from cold diuresis

06Diagnostic Tests/dt72

Scoring Systems

›HOPE Score (Hypothermia Outcome Prediction after ECLS)

›Variables: age, sex, asphyxia mechanism, CPR duration, serum K+, core temperature

›Score < 0.1 predicts mortality in adults on ECLS

›Validated in ECLS-treated hypothermic cardiac arrest patients

›Used to guide ECLS candidacy discussion

›Should not be used in isolation to withhold ECLS

›ICE Score (International Accidental Hypothermia ECLS Score)

›Variables: sex, asphyxia mechanism, serum K+

›Score > 12 predicts survival to hospital discharge

›Simpler scoring tool with fewer variables

›Complements HOPE score in decision-making

›Revised Swiss Staging System

›Clinical staging when core temperature unavailable

›Stage I: conscious, shivering — mild hypothermia

›Stage II: impaired consciousness, no shivering — moderate hypothermia

›Stage III: unconscious, vital signs present — severe hypothermia

›Stage IV: no vital signs — severe hypothermia with cardiac arrest

›AVPU-based rapid field triage tool

›Guides rewarming urgency and transport decision

›ECG scoring

›Osborn J wave amplitude correlates with depth of hypothermia

›Present in approximately 53% of hypothermic patients

›Not pathognomonic of irreversibility — treat aggressively

MRI

›MRI brain

›Limited role in acute severe hypothermia resuscitation

›Unstable patient — access contraindicated

07Disposition/dispo33

ICU admission — all severe hypothermia

›ICU-level care mandatory for all patients with core temp < 28 degrees C

›Continuous cardiac monitoring for arrhythmia and rewarming

›VF may recur during rewarming

›ECG changes require continuous telemetry

›Arterial line for continuous blood pressure and serial labs

›Central venous access for vasopressors and CVP monitoring

ECLS transfer criteria

›Transfer to ECLS-capable centre when

›Hypothermic cardiac arrest with K+ < 12 mmol/L

›Survivable arrest by potassium criterion

›Initiate CPR and transport simultaneously

›Cardiac instability with core temp < 28 degrees C

›SBP < 90 mmHg or ventricular arrhythmias

›Bypass non-ECLS hospitals

›Failure to achieve ROSC with conventional rewarming

›Continue mechanical CPR during transport

›Pre-notify ECMO team en route

›Transfer logistics

›Contact receiving hospital ECMO team before departure

›Document last serum K+ and time of arrest

›Mechanical CPR device for transport

Concurrent consults

›Mandatory specialist involvement

›Cardiac surgery or intensivist for ECLS candidacy — immediate

›Endocrinology for myxedema coma or adrenal crisis

›Nephrology if AKI or severe electrolyte abnormalities

›Trauma surgery for concurrent injuries

08Treatment/t90

Immediate interventions

›Handle with care protocol

›Minimal movement to prevent VF

›Log roll with full body support

›Avoid jarring, percussive movements

›Horizontal positioning maintained throughout

›Airway management

›Warmed humidified oxygen immediately

›40 to 42 degrees C via heated circuit

›Contributes 1 to 2 degrees C per hour rewarming

›RSI for GCS <= 8 or inability to protect airway

›Ketamine 1 to 2 mg/kg IV — maintains cardiac output

›Succinylcholine or rocuronium for paralysis

›Video laryngoscopy preferred — oral secretions and reduced neck mobility

Active external and minimally invasive rewarming

›Forced-air warming

›Bair Hugger warming blanket to trunk

›Temperature setting 43 degrees C

›Expected rewarming rate 1 to 2 degrees C per hour

›Chemical heat packs to axillae and inguinal regions

›Wrap to prevent burns

›Warmed IV fluids

›Normal saline at 40 to 42 degrees C

›Volume: 500 to 1000 mL initial bolus for hypovolemia

›Rate titrated to perfusion and urine output

›Avoid lactated Ringer's — hypothermic liver cannot metabolise lactate

›Add dextrose if hypoglycemia confirmed

›Dextrose 50% 50 mL IV push

›Maintenance dextrose 5% in NS for ongoing hypoglycemia

Cardiac arrest management

›CPR protocol for hypothermic arrest

›Standard 30:2 compression-to-ventilation ratio

›Chest wall rigidity may increase required compression force

›Mechanical CPR device for prolonged resuscitation

›Defibrillation attempts

›1 attempt at standard biphasic energy (200 J)

›If VF persists and temp < 30 degrees C, defer further shocks

›Resume defibrillation every 30 to 45 minutes as temperature rises

›Drug therapy in arrest

›Vasopressors — limited efficacy below 30 degrees C

›AHA 2025: no recommendation for or against epinephrine in hypothermic arrest

›WMS: consider withholding epinephrine at temp < 30 degrees C

›If given: standard epinephrine 1 mg IV every 3 to 5 minutes

›Antiarrhythmics

›No recommendation for or against amiodarone in hypothermic VF

›Amiodarone may accumulate and cause toxicity on rewarming

›Maximum 3 defibrillation attempts before rewarming if using WMS protocol

ECLS management

›ECMO/ECLS protocol

›Cannulation — standard femoral-femoral veno-arterial ECMO

›Bilateral femoral vein and femoral artery cannulation

›Pump flow: 3 to 5 L/min to maintain perfusion

›Circuit temperature control

›Initial circuit temperature set to 37 to 38 degrees C

›Rewarming rate not to exceed 5 degrees C per hour

›Overly rapid rewarming increases cerebral oedema risk

›Anticoagulation on ECMO

›Heparin infusion to maintain ACT 180 to 220 seconds

›Adjust for pre-existing coagulopathy

›Weaning criteria

›Core temp >= 35 degrees C

›Restoration of cardiac output and stable rhythm

›ECMO support reduced gradually over 1 to 2 hours

Electrolyte and metabolic management

›Potassium management

›Hypokalemia on presentation — intracellular shift

›Cautious potassium replacement: 10 to 20 mmol/hr IV

›Recheck every 1 to 2 hours

›Hyperkalemia during rewarming — cell lysis release

›No specific treatment unless K+ causes haemodynamic instability

›ECLS will clear potassium via dialysis circuit if added

›Glucose management

›Hypoglycemia: dextrose 50% 50 mL IV stat then maintenance dextrose infusion

›Hyperglycemia: insulin resistance common in hypothermia

›Avoid aggressive insulin therapy while hypothermic

›Reassess after rewarming

›Coagulopathy management

›Rewarming is the primary treatment for hypothermic coagulopathy

›Enzymatic coagulation function restores with normothermia

›Blood product support for active bleeding

›Fresh frozen plasma 15 mL/kg for clinical bleeding with elevated PT/PTT

›Cryoprecipitate if fibrinogen < 1.5 g/L

›Platelets if count < 50 x 10^9/L with active bleeding

Treatment of secondary causes

›Myxedema coma protocol

›Levothyroxine 200 to 400 mcg IV loading dose

›Followed by 50 to 100 mcg IV daily maintenance

›T3 (liothyronine) 5 to 20 mcg IV as adjunct in severe cases

›Hydrocortisone 100 mg IV every 8 hours

›Administer before thyroid hormone to prevent adrenal crisis precipitation

›Active rewarming concurrently

›Sepsis concurrent treatment

›Broad-spectrum antibiotics within 1 hour

›Piperacillin-tazobactam 4.5 g IV every 6 hours for community-acquired

›Add vancomycin 15 to 20 mg/kg IV if MRSA risk

›Blood cultures before antibiotics when feasible

09Special Populations/sp70

Pregnancy

›Physiological differences in pregnancy

›Increased metabolic rate provides some thermogenic protection

›Shivering thermogenesis intact unless severe hypothermia

›Placental circulation may be compromised before maternal haemodynamics deteriorate

›Increased aspiration risk

›Delayed gastric emptying

›Elevated intraabdominal pressure

›Maternal rewarming priorities

›Aggressive rewarming to protect fetal perfusion

›Left lateral tilt to relieve aortocaval compression if >= 20 weeks

›Continuous fetal heart rate monitoring when viable gestation

›Imaging approach

›Chest X-ray with fetal shielding when indicated

›CT only when benefit to mother clearly outweighs fetal radiation risk

›Medication safety

›Warmed IV normal saline — preferred volume resuscitation

›Epinephrine — use standard dosing in cardiac arrest

›Fetal risk secondary to maternal survival priority

›Vasopressors: norepinephrine or epinephrine as first-line

›Vasopressin — limited data in pregnancy

›Avoid QT-prolonging antiarrhythmics — increased maternal and fetal risk

›Delivery consideration

›Perimortem caesarean section if arrest and >= 20 weeks and no ROSC after 5 minutes

›Improves maternal venous return and CPR effectiveness

›Fetal survival depends on gestational age and arrest duration

Geriatric

›Impaired thermoregulatory reserve

›Reduced shivering thermogenesis

›Shivering may be absent even at temperatures > 30 degrees C

›Delayed recognition of hypothermia

›Impaired vasoconstriction — blunted peripheral heat conservation

›Reduced cardiac reserve for compensatory tachycardia

›Polypharmacy and drug interactions

›Beta-blockers prevent compensatory tachycardia

›Antipsychotics impair hypothalamic thermoregulation

›Sedatives and opioids accelerate heat loss

›Review and hold offending agents after stabilization

›Co-morbidity burden

›Hypothyroidism more prevalent — higher myxedema coma risk

›Adrenal insufficiency — secondary hypothermia more common in elderly

›Renal dosing adjustments mandatory for all renally-cleared drugs

›Estimated GFR calculation and medication review

›Atypical presentation pattern

›Afebrile infection as precipitant — avoid missing sepsis trigger

›Delirium as primary presentation

›Hypothermia in warm climates in elderly strongly suggests secondary cause

Pediatrics

›Unique vulnerability

›High body surface area to mass ratio — rapid heat loss

›Neonates most vulnerable — no shivering thermogenesis below 3 months

›Infants cool faster than adults in equivalent environments

›Non-shivering thermogenesis via brown adipose tissue

›Present in neonates and infants

›Depleted with prolonged cold exposure

›Temperature thresholds in children

›Severe hypothermia: core temp < 28 degrees C in children same as adults

›Swiss staging applies to pediatric patients

›Resuscitation modifications

›Defibrillation: 4 J/kg biphasic first shock

›Same threshold considerations for deferral as adults

›Epinephrine: 0.01 mg/kg IV (0.1 mL/kg of 1:10,000 solution)

›Mechanical CPR: adult devices not suitable for children < 40 kg

›Manual CPR required for small children

›Rewarming approaches in children

›Warmed IV fluids: 10 to 20 mL/kg bolus of normal saline at 40 degrees C

›Forced-air warming appropriate for all ages

›ECMO for pediatric hypothermic arrest with survivable potassium

›Pediatric ECMO cannula sizing according to weight

›Drug dosing (weight-based)

›Glucose supplementation: dextrose 10% 5 mL/kg IV for hypoglycemia in neonates

›Ketamine for airway: 1 to 2 mg/kg IV

›Rocuronium for RSI: 1.2 mg/kg IV

10Background/b92

Epidemiology

›Incidence and burden

›Exact incidence underreported — many deaths attributed to underlying cause

›Approximately 1500 deaths annually attributed to hypothermia in the United States

›Avalanche fatalities represent a significant subgroup in mountain regions

›High-risk groups

›Extremes of age — infants and elderly disproportionately affected

›Homeless populations — chronic exposure and limited shelter access

›Alcohol and substance users — estimated 30 to 50% of cases involve intoxication

›Seasonal and geographic patterns

›Northern climates — winter peak mortality

›Cold water submersion — year-round risk in all climates

›Outcomes

›Survival rates with ECLS for hypothermic cardiac arrest up to 60% in selected series

›Full neurological recovery possible even after prolonged arrest

›Potassium level strongest predictor of ECLS outcome

›Survival reported after arrest duration > 6 hours

›Reflects neuroprotective metabolic suppression

›Coldest accidental hypothermia survivor had core temp of 11.8 degrees C

›Secondary hypothermia (from myxedema, sepsis) carries higher mortality than primary environmental hypothermia

›Myxedema coma mortality 30 to 60% without treatment

›Hypothermic sepsis: independent predictor of 28-day mortality

Pathophysiology

›Thermoregulatory failure sequence

›Mild hypothermia: 32 to 35 degrees C

›Vigorous shivering, vasoconstriction, tachycardia

›Increased metabolic rate to generate heat

›Moderate hypothermia: 28 to 32 degrees C

›Shivering ceases

›Progressive bradycardia and decreased cardiac output

›Atrial fibrillation common below 32 degrees C

›Severe hypothermia: < 28 degrees C

›Coma and absent protective reflexes

›VF risk highest

›Metabolism drops approximately 7% per 1 degree C decline

›Cardiovascular effects

›Progressive bradycardia from sinus node suppression

›PR interval prolongation

›QRS widening and QT prolongation

›Osborn J waves — positive deflections at QRS-ST junction in 53% of patients

›VF threshold lowered by hypoxia, acidosis, and mechanical stimulation

›Ventricular fibrillation: primary cause of death in unrescued severe hypothermia

›Cardiac drug unresponsiveness

›Vasopressors and antiarrhythmics ineffective below 30 degrees C

›Pacemakers fail to capture below 30 degrees C

›Metabolic effects

›Neuroprotection

›Metabolic suppression reduces oxygen demand

›5 to 10 minutes of normothermic arrest leads to brain death

›Hypothermia extends survivable arrest duration dramatically

›Cold diuresis

›Peripheral vasoconstriction increases central blood volume

›Hypothalamus suppresses ADH — osmotic diuresis

›Hypovolemia and electrolyte depletion result

›Coagulopathy

›Enzyme activity reduced — all coagulation cascade steps impaired

›Platelet function reduced — adhesion and aggregation impaired

›Standard INR at 37 degrees C underestimates true coagulopathy

›Rhabdomyolysis

›Prolonged muscular activity during shivering

›Direct cold injury to muscle fibres

›Myoglobinuria and AKI risk

›Afterdrop mechanism

›Cold peripheral blood returns to core circulation after rescue and movement

›Core temperature may fall an additional 1 to 2 degrees C after rescue

›Avoid unnecessary patient movement and peripheral warming early

Therapeutic Considerations

›Rewarming rate

›Target < 5 degrees C per hour on ECLS

›Rapid rewarming associated with cerebral oedema and worse neurological outcomes

›Passive afterdrop of temperature monitored continuously

›Conventional rewarming target 1 to 2 degrees C per hour

›Active external plus minimally invasive methods combined

›Drug pharmacology in hypothermia

›Reduced drug metabolism — hepatic enzyme activity temperature-dependent

›Drugs accumulate during hypothermia; risk of toxicity on rewarming

›Increased protein binding — reduced free drug fraction

›QT-prolonging drugs strictly avoided

›Hypothermia already prolongs QT interval

›Torsades de pointes risk substantially increased

›Potassium as therapeutic guide

›K+ < 12 mmol/L: resuscitation mandatory; ECLS indicated if available

›K+ >= 12 mmol/L: futility consideration; clinical context required

›K+ serial measurement during rewarming guides electrolyte replacement

›ECLS versus conventional rewarming

›ECMO superior to cardiopulmonary bypass by 41% survival probability

›Provides reliable perfusion support during rewarming

›Allows simultaneous oxygenation and circulatory support

›Conventional invasive rewarming (lavage) reserved for ECLS-unavailable settings

›Thoracic or peritoneal lavage as bridge

›Post-resuscitation care

›Monitor for rebound hyperkalemia from cell lysis during rewarming

›DIC surveillance — coagulation profile every 6 to 8 hours

›Neurological prognosis deferred — cannot assess until normothermic and off sedation

›MRI brain after rewarming for hypoxic-ischaemic injury grading

11Patient Discharge Instructions/pdi30

copy discharge instructions

›Recovery instructions after hypothermia

›Complete rest for the first 24 to 48 hours after discharge

›Warm fluids and regular meals to restore energy stores

›Avoid alcohol — causes blood vessel dilation and heat loss

›Avoid cold environments until cleared by your doctor

›Warning signs — return to emergency immediately

›Chest pain or palpitations

›Shortness of breath or difficulty breathing

›Confusion, unusual sleepiness, or difficulty speaking

›Inability to move or extreme weakness in arms or legs

›Dark brown or red-coloured urine — possible muscle breakdown

›Severe swelling or pain in hands, feet, or extremities

›Little to no urine output

›Feeling very cold again despite being indoors

›Skin and extremity care

›Frostbite areas — do not rub or apply direct heat

›Keep area loosely bandaged

›Follow specialist instructions for wound care

›Blistered areas — do not pop blisters; see specialist

›Prevention advice

›Layer clothing in cold weather — moisture-wicking base, insulating middle, wind-resistant outer

›Stay dry — wet clothing conducts heat away from the body

›Avoid alcohol before outdoor activity in cold weather

›Tell someone your plans when going outdoors in cold weather

›Buddy system in cold environments

›Follow-up appointments

›Primary care or specialist follow-up within 3 to 5 days

12References/r29

Guidelines and key sources

›Primary guidelines

›AHA 2025 Guidelines — Part 10: Adult and Pediatric Special Circumstances of Resuscitation (Cao D et al., Circulation 2025)

›ECLS recommendation for hypothermic cardiac arrest

›Potassium threshold guidance for futility

›Wilderness Medical Society Clinical Practice Guidelines for Accidental Hypothermia: 2019 Update (Dow J et al., Wilderness Environ Med 2019)

›Field rewarming protocols

›Defibrillation deferral threshold at < 30 degrees C

›European Resuscitation Council Guidelines (Soar J et al., Lancet 2021)

›Hypothermic cardiac arrest management

›ECLS transfer criteria

Landmark trials and reviews

›Key publications

›Brown DJ et al., NEJM 2012 — Accidental Hypothermia (landmark review)

›Pathophysiology, classification, rewarming strategies

›Mendrala K et al., JAMA 2025 — ECLS in Accidental Hypothermia

›Survival outcomes with ECMO, coldest reported survivor 11.8 degrees C

›Paal P et al., Int J Environ Res Public Health 2022 — Accidental Hypothermia 2021 Update

›Swiss staging, HOPE score, myxedema overlap

›Okumura H et al., Am J Emerg Med 2025 — ECG Patterns of Accidental Hypothermia

›Osborn wave prevalence 53%, QT prolongation 49%, AF 21%

›Buse S et al., Resuscitation 2017 — Potassium and hypothermia systematic review

›K+ >= 12 mmol/L futility threshold evidence

Coding references

›ICD-10 codes

›T68 — Hypothermia

›T68.XXXA — initial encounter

›T68.XXXD — subsequent encounter

Learn More: Hypothermia (Severe)→

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Reviewed by SymptomDx Medical Team · Last reviewed August 18, 2026

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