Accidental hypothermia: Difference between revisions

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==Background==
==Background==
'''Definition: Core Temp <35C (95F)'''
[[File:Windchill21.gif|thumb|Whid chill chart]]
*Unintentional hypothermia (core cooling <35C) is associated with significant morbidity and mortality.  Roughly 1500 persons die of accidental hypothermia in the US annually.<ref>Baumgartner EA, Belson M, Rubin C, Patel M. Hypothermia and other cold-related morbidity emergency department visits: United States, 1995-2004. Wilderness Environ Med 2008;19:233-237</ref>   
===Definition: Core Temperature <35°C (95°F)===
*Despite the high mortality associated with pre-hospital arrest, well directed treatment can result in complete neurologic recovery in the hypothermic patient.<ref>Friberg H, Rundgren. Submersion, accidental hypothermia,and cardiac arrest, mechanical chest compressions as a bridge to final treatment: a case report. Scand J Trauma Resusc Emerg Med. 2009; 17: 7</ref>
*Unintentional hypothermia (core cooling <35°C) is associated with significant morbidity and mortality.  Roughly 1500 persons die of accidental hypothermia in the US annually.<ref>Baumgartner EA, Belson M, Rubin C, Patel M. [[Hypothermia]]and other cold-related morbidity emergency department visits: United States, 1995-2004. Wilderness Environ Med 2008;19:233-237</ref>   
*50% who die of hypothermia are >65 years old<ref>1. Centers for Disease Control and Prevention: Hypothermia-related deaths—United States, 2003–2004. MMWR Morb Mortal Wkly Rep 54: 173, 2005</ref>
*Despite the high mortality associated with pre-hospital arrest, well-directed treatment can result in complete neurologic recovery in the hypothermic patient.<ref>Friberg H, Rundgren. Submersion, accidental hypothermia, and cardiac arrest, mechanical chest compressions as a bridge to final treatment: a case report. Scand J Trauma Resusc Emerg Med. 2009; 17: 7</ref>
*Risk of cardiac arrest increased with temp <32C, as stable cardiac rhythms can quickly degenerate into unstable rhythms.  Hypothermic patient patient without a pulse must be managed differently due to physiology changes that occur at low temperatures.  
*50% who die of hypothermia are >65 years old<ref>Centers for Disease Control and Prevention: Hypothermia-related deaths—United States, 2003–2004. MMWR Morb Mortal Wkly Rep 54: 173, 2005</ref>
*Risk of cardiac arrest increased with temperature <32°C, as stable cardiac rhythms can quickly degenerate into unstable rhythms.  Hypothermic patient without a pulse must be managed differently due to physiology changes that occur at low temperatures. Defibrillation and many medications may be ineffective until the core temperature is above 30.0°C. If defibrillation is warranted but unsuccessful, active rewarming should be initiated while CPR is continued.  


====Scenarios and Risk Factors====
===Causes of Hypothermia===
*Avalanche victims
*Increased heat loss
*Homeless population
**Environmental exposure
*Intoxicated patients
***Avalanche victims
*Elderly patients -> particularly low income during winter months
***Homeless population
*Submersion injuries
***Elderly patients particularly low income during winter months
***[[Submersion injuries]]
**Induced vasodilation
***Drugs
***[[Carbon monoxide]]
***[[Alcohol intoxication]]
*Decreased heat production
**Endocrine
***[[Hypopituitarism]]
***[[Hypothyroidism]]
***[[adrenal insufficiency|Hypoadrenalism]]
***[[Hypoglycemia]]
**Neuromuscular inefficiency
***Extremes of age
***Impaired shivering
**Erythrodermas
***[[Psoriasis]]
***[[exfoliative erythroderma|Exfoliative dermatitis]]
***Ichthyosis
***[[Eczema]]
***[[Burns]]
**Impaired Thermoregulation
**Other
***[[Sepsis]]
***[[Trauma]]


==Clinical Features==
==Clinical Features==
{{Swiss staging system}}
{{Swiss staging system}}
==Complications==
*[[Acid-base disorders]]
*"Afterdrop"
**Initial drop in temperature and MAP as rewarming is started due to loss of vasoconstriction/AV shunting colder peripheral tissues
*[[Aspiration pneumonia and pneumonitis|Aspiration pneumonia]]
*[[coagulopathy|Bleeding]]
**Decreased platelet function and inhibition of coagulation cascade
*[[Cold injuries]]
*[[Dysrhythmias]]
*[[Disseminated Intravascular Coagulation (DIC)|Disseminated Intravascular Coagulation]]
*Hypothermia induced [[coagulopathy]]
*[[Pancreatitis]]
*[[Rhabdomyolysis]]
*[[Thromboembolism]]
**Secondary to hemoconcentration, increased blood viscosity, and poor circulation
*Ineffective Drugs
**Protein binding increases as body temperature drops, and most drugs become ineffective
**Pharmacologic manipulation of the pulse and blood pressure generally should be avoided
**Oral meds poorly absorbed because of decreased gastrointestinal motility
**Intramuscular route avoided due to poor absorption from vasoconstricted sites


==Differential Diagnosis==
==Differential Diagnosis==
{{Cold injuries DDX}}
{{Cold injuries DDX}}


==Diagnosis==
==Evaluation==
*'''Use low-reading thermometer'''
*'''Use low-reading thermometer'''
**Some standard thermometers record only to 34C
**Some standard thermometers record only to 34°C
**Measure core temp with esophageal probe if intubated (most accurate)
**Measure core temperature with esophageal probe if intubated (most accurate)
*Check blood glucose as can be very high in [[DM]] or [[CVA]] or low when metabolized to keep warm
*Check blood glucose as can be very high in [[DM]] or [[CVA]] or low when metabolized to keep warm
*Potassium >10-12 mEq/L not compatible with life
*Potassium >10-12 mEq/L not compatible with life
*Coagulopathy:  clotting factor activity and platelet function significantly reduced at temp < 34C
*Coagulopathy:  clotting factor activity and platelet function significantly reduced at temperature < 34°C
**Blood is rewarmed for lab testing so results may appear normal
**Blood is rewarmed for lab testing so results may appear normal
*If ABG is rewarmed before analysis, results will be different from patient's actual acid/base state
**Refer to [[therapeutic hypothermia]] for over and underestimations


===[[ECG]]===
===[[ECG]]===
[[File:Osborn wave.gif|thumb]]
[[File:Osborn wave.gif|thumb]]
*Typical sequence is sinus brady > a fib with slow ventricular response > v-fib > asystole
[[File:HypothermiaECG.jpg|thumb|Atrial fibrillation and Osborn J waves in a person with hypothermia.]]
*Typical sequence is sinus bradycardia → atrial fibrillation with slow ventricular response → ventricular fibrillation → asystole
*Other ECG findings:
*Other ECG findings:
**Osborn (J) wave
**Osborn (J) wave - Size of wave correlates with degree of hypothermia. No prognostic value.
**Muscle tremor artifact
**T-wave inversions
**T-wave inversions
**PR, QRS, [[QT prolongation]]
**PR, QRS, [[QT prolongation]]
**Muscle tremor artifact
**[[ST segment elevation]] or depression
**AV block
**AV block
**[[PVC]]s
**[[PVC]]s
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*Handle patient gently
*Handle patient gently
*[[V-fib]] may be induced by rough handling of patient due to irritable myocardium (anecdotal)
*[[V-fib]] may be induced by rough handling of patient due to irritable myocardium (anecdotal)
===O2===
===[[O2]]===
*Hypothermia causes leftward shift of oxyhemoglobin dissociation curve
*[[Hypothermia]] causes leftward shift of oxyhemoglobin dissociation curve
*[[Intubation]]
*[[Intubation]]
*Intubate gently
*Intubate gently
*if RSI is given medications may act at a slower rate
*if [[RSI]] is given medications may act at a slower rate
 
===[[IVF]]===
===[[IVF]]===
*Patients are also hypovolemic since Hypothermia > impaired renal concentrating ability > cold diuresis
*Patients are also hypovolemic since [[hypothermia]] causes impaired renal concentrating ability, in turn causing cold diuresis
*Patients are prone to [[Rhabdomyolysis|rhabdomyolysis]] and will need hydration
*Patients are prone to [[Rhabdomyolysis|rhabdomyolysis]] and will need hydration
*Intravascular volume is lost due to extravascular shift
*Intravascular volume is lost due to extravascular shift
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*Only perform if patient  truly does not have a pulse (unnecessary CPR may lead to [[V-fib]])
*Only perform if patient  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
*Spend 30-45s attempting to detect respiratory activity and pulse before starting CPR
===[[Dysrhythmias]]===
===[[Dysrhythmias]]===
*May occur spontaneously if temp <30C (86F)
*May occur spontaneously if temperature <30°C (86°F)
*Rewarming is treatment of choice
*Rewarming is treatment of choice
*Most dysrhythmias (e.g. sinus brady, [[a-fib]]/[[flutte]]r) require no other therapy
*Most dysrhythmias (e.g. sinus brady, [[a-fib]]/[[flutter]]) require no other therapy
*Activity of antiarrhythmics is unpredictable in hypothermia
*Activity of antiarrhythmics is unpredictable in hypothermia
*Hypothermic heart is relatively resistant to atropine, pacing, and countershock
*Hypothermic heart is relatively resistant to atropine, pacing, and countershock
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**May be refractory to therapy until patient is rewarmed
**May be refractory to therapy until patient is rewarmed
**Attempt defibrillation
**Attempt defibrillation
**Value of deferring repeat defibrillation until a target temperature is reached is uncertain<ref>Hoek T. 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010. 122:5829-5861</ref>
**Value of deferring repeat defibrillation until a target temperature is reached is uncertain<ref name=Hoek>Hoek T. 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010. 122:5829-5861</ref>
**Reasonable to perform further defibrillation attempts concurrent with rewarming<ref>Hoek T. 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010. 122:5829-5861</ref>
**Reasonable to perform further defibrillation attempts concurrent with rewarming<ref name=Hoek />
 
===[[Antibiotics]]===
===[[Antibiotics]]===
*Give if suspect [[sepsis]] (e.g. hypothermia fails to correct w/ rewarming measures)
*Give if suspect [[sepsis]] (e.g. hypothermia fails to correct with rewarming measures)
 
===[[Thiamine]]===
===[[Thiamine]]===
*Consider if [[Wernicke disease]] is possible cause of hypothermia (e.g. alcoholic pt)
*Consider if [[Wernicke disease]] is possible cause of hypothermia (e.g. alcoholic patient)
 
===[[Hydrocortisone]]===
===[[Hydrocortisone]]===
*Consider if patient has history of adrenal suppression or insufficiency
*Consider if patient has history of adrenal suppression or insufficiency
**100mg Hydrocortisone
**100mg Hydrocortisone
===[[Thyroxine]]===
 
===[[Levothyroxine]]===
*Consider if any suspicion for [[hypothyroidism]]/[[myxedema coma]]
*Consider if any suspicion for [[hypothyroidism]]/[[myxedema coma]]
*Could cause dysrhythmia or cardiac ischemia if not in myxedema coma
*Could cause dysrhythmia or cardiac ischemia if not in myxedema coma
===[[Hyperglycemia]]===
*Hyperglycemia common in hypothermia:
**Stimulates catecholamine induced glycogenolysis
**Inhibits insulin release and uptake by cell membranes
*Rebound hypoglycemia during rewarming can occur if clinicians too aggressively deliver exogenous insulin


==Rewarming==
==Rewarming==
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| '''Stage of Hypothermia''' || '''Recommended rewarming modality'''
| '''Stage of Hypothermia''' || '''Recommended rewarming modality'''
|-
|-
| I/ Mild: 32-35C (90-95F) || Passive external
| I/ Mild: 32-35°C (90-95°F) || Passive external
|-
|-
| II/ Moderate: 28-32C (82-90F) || Active external
| II/ Moderate: 28-32°C (82-90°F) || Active external
|-
|-
| III/ Severe: 20-28C (68-82F) || Active internal
| III/ Severe: 20-28°C (68-82°F) || Active internal
|-
|-
| IV/ Profound: <20C (68F) || As severe + modified ACLS
| IV/ Profound: <20°C (68°F) || As severe + modified ACLS
|}
|}


===Passive External===
===Passive External===
*Prevent additional losses -> remove wet clothes
*Prevent additional heat loss → Remove wet clothes
*Heated room
*Heated room
*Blankets - If patient still shivering, capable of rewarming 0.5C/hr
*Blankets - If patient still shivering, capable of rewarming 0.5°C/hr
*Hypothermia cap


===Active External===
===Active External===
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**Afterdrop: warmed vasodilated peripheral tissue allows cooler blood in extremities to circulate back to core
**Afterdrop: warmed vasodilated peripheral tissue allows cooler blood in extremities to circulate back to core
*Options:
*Options:
**Warm water immersion (Capable of 2-4C/Hr rewarming)
**Warm water immersion (Capable of 2-4°C/Hr rewarming)
**Heating blankets
**Heating blankets
**Radiant heat
**Radiant heat
**Forced air - Bair hugger (Up to 1-2.5C/Hr rewarming)
**Forced air - e.g. Bair hugger or Arctic Sun (Up to 1-2.5°C/Hr rewarming)
**Warm humidified air via facemask or endotracheal tube
**Warm humidified air via facemask or endotracheal tube


===Active Internal===
===Active Internal===
Options:
Options:
*Heated IV fluids: 38°C -42°C.
*Heated IV fluids: 38-42°C.
**Two animal studies have showed 65°C IVF via central line warmed subjects faster without side effects, but this has not been tested in humans<ref>Fildes J, Sheaff C, and Barrett J. Very hot intravenous fluid in the treatment of hypothermia. J Trauma. 1993; 35(5):683-686.</ref><ref>Sheaff CM, Fildes JJ, Keogh P, et al. Safety of 65 degrees C intravenous fluid for the treatment of hypothermia. Am J Surg. 1996; 172(1):52-55.</ref>
**Two animal studies have showed 65°C IVF via central line warmed subjects faster without side effects, but this has not been tested in humans<ref>Fildes J, Sheaff C, and Barrett J. Very hot intravenous fluid in the treatment of hypothermia. J Trauma. 1993; 35(5):683-686.</ref><ref>Sheaff CM, Fildes JJ, Keogh P, et al. Safety of 65 degrees C intravenous fluid for the treatment of hypothermia. Am J Surg. 1996; 172(1):52-55.</ref>
**If central line is placed, avoid irritating the heart
**If central line is placed, avoid irritating the heart
*GI tract lavage
*GI tract lavage
**Can cause fluid and electrolyte fluctuations, also risk of pulmonary aspiration
*[[Bladder lavage]]
*[[Bladder lavage]]
**Small surface area available for heat exchange
*[[Thoracic lavage]]
*[[Thoracic lavage]]
*Peritoneal lavage
*[[Peritoneal lavage]]
*Bypass/ECMO<ref>Ginty C, et al. Extracorporeal membrane oxygenation rewarming in the ED: an opportunity for success. American Journal of Emergency Medicine. 2014 December 3 (ahead of print).</ref>/AV Dialysis
*Bypass/[[ECMO]]<ref>Ginty C, et al. Extracorporeal membrane oxygenation rewarming in the ED: an opportunity for success. American Journal of Emergency Medicine. 2014 December 3 (ahead of print).</ref>/AV Dialysis


===Rewarming Rates===
===Rewarming Rates===
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| Shivering<ref name=Kempainen>Kempainen, R. R. and Brunette, D. D. The Evaluation and Management of Accidental Hypothermia. Respir.Care 2004;49(2):192-205 </ref>||1.5||
| Shivering<ref name=Kempainen>Kempainen, R. R. and Brunette, D. D. The Evaluation and Management of Accidental Hypothermia. Respir.Care 2004;49(2):192-205 </ref>||1.5||
|-
|-
| Warming Blanket<ref name=Kempainen>Kempainen, R. R. and Brunette, D. D. The Evaluation and Management of Accidental Hypothermia. Respir.Care 2004;49(2):192-205 </ref>||2||
| Warming Blanket<ref name=Kempainen />||2||
|-
|-
| '''Active External'''||||
| '''Active External'''||||
|-
|-
| Warm IV fluids (47C)||1-3||Highly variable; Limited by tubing distance, requires large volumes with risk of volume overload
| Warm IV fluids (47°C)||1-3||Highly variable; Limited by tubing distance, requires large volumes with risk of volume overload
|-
|-
| Forced air  (Bair hugger)||1-2.5||
| Forced air  (Bair hugger)||1-2.5||
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| Warm Humidified Air (intubated)||0.5-1.2||Low heat transport capacity
| Warm Humidified Air (intubated)||0.5-1.2||Low heat transport capacity
|-
|-
| Peritoneal Lavage<ref name=Kempainen>Kempainen, R. R. and Brunette, D. D. The Evaluation and Management of Accidental Hypothermia. Respir.Care 2004;49(2):192-205 </ref>||3||
| Peritoneal Lavage<ref name=Kempainen />||3||
|-
|-
| Thoracic Lavage<ref name=Kempainen>Kempainen, R. R. and Brunette, D. D. The Evaluation and Management of Accidental Hypothermia. Respir.Care 2004;49(2):192-205 </ref>|| 3-6||
| Thoracic Lavage<ref name=Kempainen />|| 3-6||
|-
|-
| Hemodialysis<ref name=Kempainen>Kempainen, R. R. and Brunette, D. D. The Evaluation and Management of Accidental Hypothermia. Respir.Care 2004;49(2):192-205 </ref>||3-4||
| Hemodialysis<ref name=Kempainen />||3-4||
|-
|-
| Open thoracotomy lavage||Up to 8 (median 3)||Highly invasive. 71% survival in 1 study
| Open thoracotomy lavage||Up to 8 (median 3)||Highly invasive. 71% survival in 1 study
|-
|-
| Cardiac Bypass<ref name=Kempainen>Kempainen, R. R. and Brunette, D. D. The Evaluation and Management of Accidental Hypothermia. Respir.Care 2004;49(2):192-205 </ref>||7-10||
| Cardiac Bypass<ref name=Kempainen />||7-10||
|}
|}


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*Be careful when inserting guidewires, persistent shocks can degenerate fib into asystole
*Be careful when inserting guidewires, persistent shocks can degenerate fib into asystole
*Standard [[ACLS]] guidelines may not apply:
*Standard [[ACLS]] guidelines may not apply:
*Any organized rhythm should be assumed to be perfusing the patient adequately
**Any organized rhythm should be assumed to be perfusing the patient adequately
*Starting [[CPR]] may precipitate fatal ventricular rhythms
**Starting [[CPR]] may precipitate fatal ventricular rhythms
*Modified vs. Standard ACLS:
*Modified vs. Standard ACLS:
**ERC recommends up to 3 defibrillations with [[epi] held until temp >30C, then [[epi]] interval of 6 min until temp >35C
**ERC recommends up to 3 defibrillations with [[epi]] held until temperature >30°C, then [[epinephrine]] interval of 6 min until temperature >35°C
**AHA recommends 3 defibrillations and 3 rounds of [[epi]] with further dosing guided by clinical response
**AHA recommends 3 defibrillations and 3 rounds of [[epinephrine]] with further dosing guided by clinical response
**Recent consensus suggest only one [[defibrillation]] and dose of ACLS meds -> rewarm 5C -> one defib/meds -> etc.
**Recent consensus suggest only one [[defibrillation]] and round of ACLS meds rewarm 5°C → one defib/meds → Repeat


===Termination of CPR===
===Termination of [[CPR]]===
Should be considered if:
*Should be considered if:
*K > 12 mmol
**K > 12 mmol<ref>Schaller M, Fischer AP, Perret CH. Hyperkalemia: A Prognostic Factor During Acute Severe Hypothermia. JAMA. 1990;264(14):1842–1845. doi:10.1001/jama.1990.03450140064035</ref><ref name="Paal">Paal P, Gordon L, Strapazzon G, et al. Accidental hypothermia-an update : The content of this review is endorsed by the International Commission for Mountain Emergency Medicine (ICAR MEDCOM). Scand J Trauma Resusc Emerg Med. 2016;24(1):111. Published 2016 Sep 15. doi:10.1186/s13049-016-0303-7</ref>
*[[Asystole]] persists beyond >32C
**[[Asystole]] persists beyond >32°C
*Lactate and pH have less consistent prognostic significance in hypothermia
*''Lactate and pH have less consistent prognostic significance in hypothermia''


==Disposition==
==Disposition==
 
*ICU for severe cases
==Complications==
*[[Acid-base disorders]]
*"Afterdrop"
**Initial drop in temp and MAP as rewarming is started due to loss of vasoconstriction/AV shunting colder peripheral tissues
*[[Aspiration pneumonia and pneumonitis|Aspiration pneumonia]]
*Bleeding
**Decreased platelet function and inhibition of coagulation cascade
*[[Cold injuries]]
*[[Dysrhythmias]]
*[[Disseminated Intravascular Coagulation (DIC)|Disseminated Intravascular Coagulation]]
*[[Pancreatitis]]
*[[Rhabdomyolysis]]
*[[Thromboembolism]]
**Secondary to hemoconcentration, increased blood viscosity, and poor circulation
*Ineffective Drugs
**Protein binding increases as body temperature drops, and most drugs become ineffective
**Pharmacologic manipulation of the pulse and blood pressure generally should be avoided
**Orally meds poorly absorbed because of decreased gastrointestinal motility
**Intramuscular route avoided due to poor absorption from vasoconstricted sites


==External Links==
==External Links==
*[http://lifeinthefastlane.com/ecg-library/basics/hypothermia/ LITFL Hypothermia]
*[http://lifeinthefastlane.com/ecg-library/basics/hypothermia/ LITFL Hypothermia]
*[http://dhss.alaska.gov/dph/Emergency/Documents/ems/documents/Alaska%20DHSS%20EMS%20Cold%20Injuries%20Guidelines%20June%202014.pdf Alaska Cold Injury Guidelines]
*[http://dhss.alaska.gov/dph/Emergency/Documents/ems/documents/Alaska%20DHSS%20EMS%20Cold%20Injuries%20Guidelines%20June%202014.pdf Alaska Cold Injury Guidelines]
*[https://emcrit.org/ibcc/hypothermia/ IBCC Hypothermia]


==See Also==
==See Also==
*[[Cold injuries]]
*[[Therapeutic hypothermia]]
*[[Therapeutic hypothermia]]
*[[Water-related injuries]]
*[[Water-related injuries]]

Revision as of 19:52, 3 November 2021

Background

Whid chill chart

Definition: Core Temperature <35°C (95°F)

  • Unintentional hypothermia (core cooling <35°C) is associated with significant morbidity and mortality. Roughly 1500 persons die of accidental hypothermia in the US annually.[1]
  • Despite the high mortality associated with pre-hospital arrest, well-directed treatment can result in complete neurologic recovery in the hypothermic patient.[2]
  • 50% who die of hypothermia are >65 years old[3]
  • Risk of cardiac arrest increased with temperature <32°C, as stable cardiac rhythms can quickly degenerate into unstable rhythms. Hypothermic patient without a pulse must be managed differently due to physiology changes that occur at low temperatures. Defibrillation and many medications may be ineffective until the core temperature is above 30.0°C. If defibrillation is warranted but unsuccessful, active rewarming should be initiated while CPR is continued.

Causes of Hypothermia

Clinical Features

Swiss Hypothermia Staging System[4]

Classification Temperature Signs/Symptoms
I / Mild 32-35°C (90-95°F) Shivering, awake
II / Moderate 28-32°C (82-90°F) Shivering, depressed mental status
III / Severe 20-28°C (68-82°F) unconscious/severely depressed mental status, shivering ceases
IV / Profound <20°C (68°F) unobtainable VS


Complications

  • Acid-base disorders
  • "Afterdrop"
    • Initial drop in temperature and MAP as rewarming is started due to loss of vasoconstriction/AV shunting colder peripheral tissues
  • Aspiration pneumonia
  • Bleeding
    • Decreased platelet function and inhibition of coagulation cascade
  • Cold injuries
  • Dysrhythmias
  • Disseminated Intravascular Coagulation
  • Hypothermia induced coagulopathy
  • Pancreatitis
  • Rhabdomyolysis
  • Thromboembolism
    • Secondary to hemoconcentration, increased blood viscosity, and poor circulation
  • Ineffective Drugs
    • Protein binding increases as body temperature drops, and most drugs become ineffective
    • Pharmacologic manipulation of the pulse and blood pressure generally should be avoided
    • Oral meds poorly absorbed because of decreased gastrointestinal motility
    • Intramuscular route avoided due to poor absorption from vasoconstricted sites

Differential Diagnosis

Cold injuries

Evaluation

  • Use low-reading thermometer
    • Some standard thermometers record only to 34°C
    • Measure core temperature with esophageal probe if intubated (most accurate)
  • Check blood glucose as can be very high in DM or CVA or low when metabolized to keep warm
  • Potassium >10-12 mEq/L not compatible with life
  • Coagulopathy: clotting factor activity and platelet function significantly reduced at temperature < 34°C
    • Blood is rewarmed for lab testing so results may appear normal
  • If ABG is rewarmed before analysis, results will be different from patient's actual acid/base state

ECG

Osborn wave.gif
Atrial fibrillation and Osborn J waves in a person with hypothermia.
  • Typical sequence is sinus bradycardia → atrial fibrillation with slow ventricular response → ventricular fibrillation → asystole
  • Other ECG findings:
    • Osborn (J) wave - Size of wave correlates with degree of hypothermia. No prognostic value.
    • Muscle tremor artifact
    • T-wave inversions
    • PR, QRS, QT prolongation
    • ST segment elevation or depression
    • AV block
    • PVCs

General Management

Handling

  • Handle patient gently
  • V-fib may be induced by rough handling of patient due to irritable myocardium (anecdotal)

O2

  • Hypothermia causes leftward shift of oxyhemoglobin dissociation curve
  • Intubation
  • Intubate gently
  • if RSI is given medications may act at a slower rate

IVF

  • Patients are also hypovolemic since hypothermia causes impaired renal concentrating ability, in turn causing cold diuresis
  • Patients are prone to rhabdomyolysis and will need hydration
  • Intravascular volume is lost due to extravascular shift
  • NS preferred over LR as cold liver poorly metabolizes LR

CPR

  • Only perform if patient 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

Dysrhythmias

  • May occur spontaneously if temperature <30°C (86°F)
  • 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
  • Ventricular tachycardia or Ventricular fibrillation are most common
    • May be refractory to therapy until patient is rewarmed
    • Attempt defibrillation
    • Value of deferring repeat defibrillation until a target temperature is reached is uncertain[5]
    • Reasonable to perform further defibrillation attempts concurrent with rewarming[5]

Antibiotics

  • Give if suspect sepsis (e.g. hypothermia fails to correct with rewarming measures)

Thiamine

  • Consider if Wernicke disease is possible cause of hypothermia (e.g. alcoholic patient)

Hydrocortisone

  • Consider if patient has history of adrenal suppression or insufficiency
    • 100mg Hydrocortisone

Levothyroxine

Hyperglycemia

  • Hyperglycemia common in hypothermia:
    • Stimulates catecholamine induced glycogenolysis
    • Inhibits insulin release and uptake by cell membranes
  • Rebound hypoglycemia during rewarming can occur if clinicians too aggressively deliver exogenous insulin

Rewarming

Recommendations on Rewarming Modality based on Temperature and Clinical picture

Stage of Hypothermia Recommended rewarming modality
I/ Mild: 32-35°C (90-95°F) Passive external
II/ Moderate: 28-32°C (82-90°F) Active external
III/ Severe: 20-28°C (68-82°F) Active internal
IV/ Profound: <20°C (68°F) As severe + modified ACLS

Passive External

  • Prevent additional heat loss → Remove wet clothes
  • Heated room
  • Blankets - If patient still shivering, capable of rewarming 0.5°C/hr
  • Hypothermia cap

Active External

  • Rewarm trunk BEFORE the extremities, otherwise you cause further hypotension ("core temperature afterdrop")
    • Afterdrop: warmed vasodilated peripheral tissue allows cooler blood in extremities to circulate back to core
  • Options:
    • Warm water immersion (Capable of 2-4°C/Hr rewarming)
    • Heating blankets
    • Radiant heat
    • Forced air - e.g. Bair hugger or Arctic Sun (Up to 1-2.5°C/Hr rewarming)
    • Warm humidified air via facemask or endotracheal tube

Active Internal

Options:

  • Heated IV fluids: 38-42°C.
    • Two animal studies have showed 65°C IVF via central line warmed subjects faster without side effects, but this has not been tested in humans[6][7]
    • If central line is placed, avoid irritating the heart
  • GI tract lavage
    • Can cause fluid and electrolyte fluctuations, also risk of pulmonary aspiration
  • Bladder lavage
    • Small surface area available for heat exchange
  • Thoracic lavage
  • Peritoneal lavage
  • Bypass/ECMO[8]/AV Dialysis

Rewarming Rates

Mode °C/Hr Comments
Passive External
Shivering[9] 1.5
Warming Blanket[9] 2
Active External
Warm IV fluids (47°C) 1-3 Highly variable; Limited by tubing distance, requires large volumes with risk of volume overload
Forced air (Bair hugger) 1-2.5
Warm water immersion 2-4
Active Internal
Warm Humidified Air (intubated) 0.5-1.2 Low heat transport capacity
Peritoneal Lavage[9] 3
Thoracic Lavage[9] 3-6
Hemodialysis[9] 3-4
Open thoracotomy lavage Up to 8 (median 3) Highly invasive. 71% survival in 1 study
Cardiac Bypass[9] 7-10

Management of the coding hypothermic patient

  • Rhythms can quickly degenerate into unstable rhythms
  • Be careful when inserting guidewires, persistent shocks can degenerate fib into asystole
  • Standard ACLS guidelines may not apply:
    • Any organized rhythm should be assumed to be perfusing the patient adequately
    • Starting CPR may precipitate fatal ventricular rhythms
  • Modified vs. Standard ACLS:
    • ERC recommends up to 3 defibrillations with epi held until temperature >30°C, then epinephrine interval of 6 min until temperature >35°C
    • AHA recommends 3 defibrillations and 3 rounds of epinephrine with further dosing guided by clinical response
    • Recent consensus suggest only one defibrillation and round of ACLS meds → rewarm 5°C → one defib/meds → Repeat

Termination of CPR

  • Should be considered if:
  • Lactate and pH have less consistent prognostic significance in hypothermia

Disposition

  • ICU for severe cases

External Links

See Also

References

  1. Baumgartner EA, Belson M, Rubin C, Patel M. Hypothermiaand other cold-related morbidity emergency department visits: United States, 1995-2004. Wilderness Environ Med 2008;19:233-237
  2. Friberg H, Rundgren. Submersion, accidental hypothermia, and cardiac arrest, mechanical chest compressions as a bridge to final treatment: a case report. Scand J Trauma Resusc Emerg Med. 2009; 17: 7
  3. Centers for Disease Control and Prevention: Hypothermia-related deaths—United States, 2003–2004. MMWR Morb Mortal Wkly Rep 54: 173, 2005
  4. Brown et al., Accidental Hypothermia. N Engl J Med 2012; 367:1930-1938
  5. 5.0 5.1 Hoek T. 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010. 122:5829-5861
  6. Fildes J, Sheaff C, and Barrett J. Very hot intravenous fluid in the treatment of hypothermia. J Trauma. 1993; 35(5):683-686.
  7. Sheaff CM, Fildes JJ, Keogh P, et al. Safety of 65 degrees C intravenous fluid for the treatment of hypothermia. Am J Surg. 1996; 172(1):52-55.
  8. Ginty C, et al. Extracorporeal membrane oxygenation rewarming in the ED: an opportunity for success. American Journal of Emergency Medicine. 2014 December 3 (ahead of print).
  9. 9.0 9.1 9.2 9.3 9.4 9.5 Kempainen, R. R. and Brunette, D. D. The Evaluation and Management of Accidental Hypothermia. Respir.Care 2004;49(2):192-205
  10. Schaller M, Fischer AP, Perret CH. Hyperkalemia: A Prognostic Factor During Acute Severe Hypothermia. JAMA. 1990;264(14):1842–1845. doi:10.1001/jama.1990.03450140064035
  11. Paal P, Gordon L, Strapazzon G, et al. Accidental hypothermia-an update : The content of this review is endorsed by the International Commission for Mountain Emergency Medicine (ICAR MEDCOM). Scand J Trauma Resusc Emerg Med. 2016;24(1):111. Published 2016 Sep 15. doi:10.1186/s13049-016-0303-7