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Accidental Hypothermia. François Dufresne McGill Emergency Medicine May 2 nd 2001. The Case of Tommy. 23h10 Call from MD working in James Bay Male, 27 y.o. Unresponsive. Found in snow, cross-country skiing Normal Airway. Breathing.  O 2 sat. Femoral pulse + (35)  BP.

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Accidental hypothermia l.jpg

Accidental Hypothermia

François Dufresne

McGill Emergency Medicine

May 2nd 2001


The case of tommy l.jpg
The Case of Tommy

  • 23h10

  • Call from MD working in James Bay

  • Male, 27 y.o. Unresponsive.

  • Found in snow, cross-country skiing

  • Normal Airway. Breathing.  O2 sat.

  • Femoral pulse + (35)  BP.

  • GCS=3 TR = 28C.

  • IV. Monitor. Mask with 100% O2


The case of tommy3 l.jpg
The Case of Tommy…

  • Friend told MD:

    •  PMH.  Rx.  drugs.  EtOH

  • Major foot deformity

  • Looks like fell in ski and could not return home by himself…

  • MD has some questions for you…


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The Case of Tommy…

  • Should he intubate? Are there risks to precipitate dysrythmias?

    • Cold myocardium prone to arythmias?

  • How should he rewarm the patient?

    • Danger of afterdrop?

  • He wants an ABG but should he ask for the blood to be warmed to normal T for analysis…or it doesn’t matter?

  • Answer: You’ll call him back…


    The case of tommy5 l.jpg
    The Case of Tommy…

    • MD calls you back 30 minutes later

    • Pt in cardiac arrest : V.fib. Now 27C

    • 3 shocks

    • Epinephrine + re-shock

    • Having Amiodarone prepared…

    • How long should he do CPR and rescussitation?

    Answer ?

    Anything wrong ?


    Introduction l.jpg
    Introduction

    • Maritime / War litterature

    • Hannibal experience in 218 B.C



    Introduction8 l.jpg
    Introduction

    • EtOH 

    • Mental illness 

    • Homelessness 

    • Province of Quebec  Cold


    Slide9 l.jpg
    Plan

    • Definitions

    • Physiology

    • Pathophysiology

    • Labs findings : ABG, ECG

    • Rewarming methods

    • Afterdrop

    • ACLS 2000 guidelines


    Definitions l.jpg
    Definitions

    • Primary VS Secondary

    • Primary

      • Normal thermoregulation

      • Overwhelming cold exposure

    • Secondary

      • Abnormal thermogenesis

      • Multiple causes


    Definitions11 l.jpg
    Definitions

    • Hypothermia : < 35C

    • Mild : 32-35C

    • Moderate : 28-32C

    • Severe : < 28C


    Physiology heat production l.jpg
    Physiology: Heat production

    • Basal metabolism (Metabolic rate)

      • Heart / Liver

    • Anterior hypothalamus

    • Thyroid / Sympathetic

    • Preshivering muscle tone (2x)

    • Shivering (2-5x)

    • Posterior hypothalamus


    Physiology heat dissipation l.jpg
    Physiology: Heat dissipation

    • Radiation (55-65%)

      • Gradient between environement and exposed body area.

  • Conduction (2-3%)

    • Direct contact with cold substance

  • Convection (10-15%)

    • Wind…

  • Evaporation (20-35%)


  • Physiology l.jpg
    Physiology…

    • Above 32C:

      • Vasoconstriction

      • Shivering

      • Basal metabolic rate

    • Below 32C:

      • No shivering

    • Below 24C:

      • No basal metabolic rate


    Pathophysiology l.jpg
    Pathophysiology

    Cardiovascular

    • Initial tachycardia

    • Gradual bradycardia : HR 50% at 28C.

    • Not consistent ?

      • Hypoglycemia, intoxication, hypovolemia,…?

    • Refractory to atropine

    •  BP  CI

    • A.fib (T < 32C)

    • V.fib (T < 28C)


    Pathophysiology16 l.jpg
    Pathophysiology…

    CNS

    • Cerebral metabolism  6% / 1C

    • Normal autoregulation until 25C

    • EEG flat at 19C

      Renal

    • Cold diuresis

      • Peripheral vasoconstriction

      • Failure to reabsorb Na+ and water.


    Pathophysiology17 l.jpg
    Pathophysiology…

    Respiratory

    • CO2 production  50% at 30C

    • Decreased RR

    • ARDS possible

      Hematology

    • Hemostasis and coagulation impaired

    • Problems with CPB


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    Mild (> 32C)

    • Increase metabolic rate

    • Maximum shivering thermogenesis

    • Amnesia / dysarthria / ataxia

    • Loss of coordination

    • Tachycardic, tachypneic

    • Normal BP


    Moderate 28 32 c l.jpg
    Moderate (28– 32C)

    • Stupor

    • No shivering

    • Bradycardic / A.fib

    •  BP  RR

    • Pupils dilated (< 30C)


    Severe 28 c l.jpg
    Severe (<28C )

    • Coma

    • No corneal or oculocephalic reflexes

    •  BP

    • V.fib (Maximum risk: 22C)

    • Apnea

    • Asystole

    • Areflexia / fixed pupils

    • Flat EEG (19C)


    Lab findings ecg l.jpg
    Lab findings : ECG

    • Woman, 75 y.o

    • Found unconscious in her apartment


    Osborn j wave l.jpg
    Osborn (J) Wave

    • Mr. John J. Osborn in the early ’50’s.

    • When T< 33C

    • 25%-30% of patients

    • Positive-negative deflection

    Osborn JJ: Experimental hypothermia: respiratory and blood pH changes in relation to cardiac function. Am J Physiol 1953; 175:389.


    Osborne j wave l.jpg
    Osborne (J) Wave…

    • Amplitude proportionnal to degree of hypothermia

    • Usually V3-V6

    • At junction of QRS and ST segment

    Osborn JJ: Experimental hypothermia: respiratory and blood pH changes in relation to cardiac function. Am J Physiol 1953; 175:389.


    Ecg in hypothermia l.jpg
    ECG in Hypothermia

    • Muscle tremors artifacts

    • Early changes

      • Bradycardia

      • T wave inversion

      • Prolonged PR, QRS and QT intervals

    • A.fib when T < 32C

    • V.fib when T < 28C


    Lab findings abg l.jpg
    Lab findings : ABG

    • Man, 45 y.o,.

    • Rectal T= 30C. LOC Intubated.

    • Acid-base status?

    • Technician asks you if he should warm the blood before analysis…

      A) Don’t warm it : 30C

      B) Warm it to 37C

      C) heu…(30+37)/2….33.5C

      D) Both and I’ll pick the best one.


    Abg in hypothermia l.jpg
    ABG in Hypothermia

    • 1st ABG (30C):

      • pH = 7.5

      • pCO2 = 27

  • 2nd ABG (37C):

    • pH = 7.4

    • pCO2 = 40

  • Which one do you pick?

  • Will you try to  RR or VT to  pCO2 ?

  • Everything’s perfect, I don’t touch the ventilator ?

  • The answer ? ….

  • The Good One !!!


    Abg in hypothermia the rationale l.jpg
    ABG in Hypothermia……the rationale

    • pH of water at any given T defines neutrality

    • H2O  H+ + OH-

    • As T , less free H+ and OH- are generated and pH of neutrality .

    • As T , CO2 content is the same but pCO2 .

    Delaney KA and al. Assessment of Acid-Base Disturbances in Hypothermia and their physiologic consequences. Ann Emerg Med, Jan 1989; 18:72-82.


    Slide31 l.jpg
    So…

    • 1st ABG (30C):

      • pH = 7.5

      • pCO2 = 27

  • 2nd ABG (37C):

    • pH = 7.4

    • pCO2 = 40


  • Abg in hypothermia the rationale32 l.jpg
    ABG in Hypothermia……the rationale

    • ABG machines usually warms blood to 37C.

    • So use the UNCORRECTED ABG for normal T .

    Delaney KA and al. Assessment of Acid-Base Disturbances in Hypothermia and their physiologic consequences. Ann Emerg Med, Jan 1989; 18:72-82.


    Rewarming methods passive rewarming l.jpg
    Rewarming methods :Passive rewarming

    • Endogenous heat production

      • Shivering, metabolic rate, TSH, sympathetic,…

    • Involves decreasing heat loss

      • Remove from cold environnement

      • Remove wet clothes

      • Provide blanket


    Passive rewarming l.jpg
    Passive rewarming…

    • O2 consumption can > 90%

    • CO2 production can by 65%

    • Possible anaerobic metabolism Rewarming rate : 0.5C - 2.0C /h

    • Method of choice for mild hypothermia

    • Adjunt for moderate hypothermia


    Rewarming methods active external rewarming l.jpg
    Rewarming methods :Active external rewarming

    • Heat to body surfaces

      • Heating blankets (fluid filled)

      • Air blankets

      • Radiant warmers

      • Immersion in hot bath

      • Water bottles / Heating pads

    • Less effective than internal rewarming if vasoconstricted +++


    Active external rewarming l.jpg
    Active external rewarming…

    • Concern about afterdrop.

    • Rewarming rates : 1C – 2.5C / h

    • Circulatory problem may be  by applying devices to trunk only.

    • Very few prospective controlled study comparing methods.


    Forced air blankets l.jpg
    Forced Air Blankets

    • ED patients

    • Moderate to severe hypothermia (< 32C)

    • Exclusion criteria

      • Cardiac arrest

      • Hypothalamic lesions

    • 16 patients

    • Randomized to passive insulation with cotton blanket or forcedair blanket @ 43C .

    Mark T. Steele and al. Forced Air Speeds Rewarming in Accidental Hypothermia, Ann Emerg Med, April 1996; 27:479-484.


    Forced air blanket l.jpg
    Forced Air Blanket…

    • All patients: warm iv fluids @ 38C

    • Warm O2 (40C)

    • End point: T = 35C

    • Looked at:

      • Rates of rewarming

      • Skin damage by blankets

    Mark T. Steele and al. Forced Air Speeds Rewarming in Accidental Hypothermia, Ann Emerg Med, April 1996; 27:479-484.


    Forced air blanket39 l.jpg
    Forced Air Blanket…

    Results

    • No afterdrop in both groups

    • No skin erythema/damage

    • Rewarming rates (p=0.01)

      • Forced-Air: 2.4C / h

      • Regularblanket: 1.4C / h

    Mark T. Steele and al. Forced Air Speeds Rewarming in Accidental Hypothermia, Ann Emerg Med, April 1996; 27:479-484.


    Slide40 l.jpg

    Forced air

    Mark T. Steele and al. Forced Air Speeds Rewarming in Accidental Hypothermia, Ann Emerg Med, April 1996; 27:479-484.


    Electrical heating blanket l.jpg
    Electrical heating blanket

    • Carbon fiber-resistive blanket

      VS Passive rewarming

    • 8 patients

    • Induced-hypothermia (33C)

    • Skin thermal flux transducer

    • CO2 concentration production through mask

    • Compared:

      • rates of rewarming

      • core heat content

    Greif R and al, Resistive heating is more effective than metallic-foil insulation in an experimental model of accidental hypothermia: a randomized controlled trial. Ann Emerg Med. April 2000; 35: 337-345.


    Electrical heating l.jpg
    Electrical heating

    Results

    • Core heat content >> electrical heating

    • Rates  1.5C/h > with electical heating

    • No afterdrop both groups

    Greif R and al, Resistive heating is more effective than metallic-foil insulation in an experimental model of accidental hypothermia: a randomized controlled trial. Ann Emerg Med. April 2000; 35: 337-345.


    Rewarming methods active internal core rewarming l.jpg
    Rewarming methods :Active internal (core) rewarming

    • Warm iv fluids

    • Warm, humid oxygen

    • Peritoneal lavage

    • Gastric / Esophageal lavage

    • Bladder / Rectal lavage

    • Pleural / Mediastinal lavage

    • Microwaves (Diathermy)

    • Extracorporeal circulatory rewarming


    Warm iv fluids l.jpg
    Warm iv fluids

    • Up to 45C shown to be safe

    • 65C fluid studied in dogs

      • Journal of Trauma 1993 (8 dogs)

      • American Journal of Surgery 1996 (10 dogs)

      • Through IVC

      • Safe. No Complications

      • 2.9C/h compared to 1.25C/h (J Trauma)

      • 3.7C/h compared to 1.75C/h (Am J Surg)


    Warm iv fluids45 l.jpg
    Warm iv fluids…

    • Saline…Not RL

    • Long tubulure = lost of heat

    • Can use microwave for saline (No D5W)

      • Annals of EM, 1984 and 1985

      • 1L of NS to 39C : 2 minutes at high power.

    • No microwave rewarming for PRBC

      • Hemolysis

      • Hemoglobinuria

      • Transfusion reaction


    Warm humidified o 2 l.jpg
    Warm, humidified O2

    • 42C-46C

    • Prevent heat loss

    • Negligible heat gain

    • Very important in management of hypothermic patient:

      • Up to 30% of heat production lost through airway.


    Gastric oesophageal bladder rectal lavage l.jpg
    Gastric/Oesophageal/ Bladder/Rectal lavage

    • Not shown to be better than external rewarming.

    • Limited surface area

    • Limited heat exchange

    • Limited utility (!)

    • Recommend as last resort when other modalities not available.


    Peritoneal lavage l.jpg
    Peritoneal lavage

    • Fluid at 40-45C

    • Up to 12 L/h

    • KCl free

    • Hepatic rewarming

    • Renal support when dialysate is used

    • 2C-4C / h

    • C.I.

      • Abdominal trauma

      • Acute abdomen

      • Free intra-abdominal air


    Peritoneal lavage49 l.jpg
    Peritoneal lavage…

    • Almost all studies before 1980

    • Almost all animal studies

    • Critical Care Medicine 1988

      • 11 dogs

      • Comparing peritoneal/pleural lavage and heated aerosol inhalation

      • Peritoneal and pleural lavage equivalent

      •  6C/h/m2

      • Heated inhalation alone : little heat gain


    Pleural lavage closed thoracic lavage continuous thoracic cavity lavage l.jpg
    Pleural lavageClosed-thoracic lavageContinuous thoracic cavity lavage

    • Two large (38F) ipsilateral chest tubes

    • 1: 2nd or 3rd anterior intercostal space, midclavicular.

    • 2: 5th or 6th intercostal space, posterior axillary line.

    • NS or tap water @ 42C

    • Rewarms heart + greater vessels

    Hall KN and al. Closed thoracic cavity lavage in the treatment of severe hypothermia in human beings. Ann Emerg Med, Feb 1990;19:204-206.


    Mediastinal lavage l.jpg
    Mediastinal lavage

    • Requires certain expertise

    • Limited clinical experience

    • Case reports

    • Internal cardiac massage

    • 8C / h

    Douglas D. Brunette, Hypothermic cardiac arrest: An 11 year review of ED management and outcome. Am J Emerg Med 2000; 18:418-422.


    Extracorporeal blood rewarming techniques l.jpg
    Extracorporeal blood rewarming techniques

    • Hemodialysis

    • Arteriovenous rewarming

    • Venovenous rewarming

    • Cardiopulmonary bypass


    Extracorporeal blood rewarming l.jpg
    Extracorporeal blood rewarming…

    • Hemodialysis : renal dysfunction

    • AV depends on the pt’s BP

    • CPB is the « Gold Standard ».

    • CPB improves long term survival and neurologic outcome.

      • 15 of 32 long term survivors and none had neurologic deficits (7 years later).

    B.H. Walpoth and al. Outcome of survivors of accidental deep hypothermia and circulatory arrest treated with extracorporeal blood warming, N Engl J Med, 1997;337:1500-5


    Diathermy l.jpg
    Diathermy

    • Ultrasonic waves

    • Microwaves

    • Short waves

    • Few studies

    • Radio wave regional hyperthermia: Experience with Tx of tumors.

    • Not widespread because of dosages in human poorly defined.


    Diathermy55 l.jpg
    Diathermy…

    • Prospective

    • Radio Wave vs. Peritoneal lavage

    • 6 dogs

    • Rate of rewarming 3x > for Radio wave.

    J.D. White and al. Controlled comparison of Radio Wave regional hyperthermia and peritoneal lavage rewarming after immersion hypthermia, J Trauma, 1985; (25)10: 989-993.


    The afterdrop phenomenon l.jpg
    The Afterdrop Phenomenon

    • Continued fall in deep core T during the initial period of rewarming.

    • First described by James Currie in 1798

    • Theory of Burton and Edholm (1955):

      • Attributed to peripheral vasodilatation

      • Return of cold blood to central circulation

      • Cooling of myocardium

    • Accepted theory until mid ’80’s

    Burton, A.C., and O.G. Edholm. Man in Cold Environment. London: Arnold, 1955, p.216.


    Paul webb an alternative explanation j appl physiol 1986 l.jpg
    Paul Webb,An alternative explanation.J. Appl. Physiol. 1986

    • Fall of T during active rewarming:

      • Up to 2C

      • 10 – 30 min

    • Used calorimeter, rectal, esophageal and tympanic probes.

    • Heat loss calculation

    Webb, Paul. Afterdrop of body temperature during rewarming: an alternative explanation. J.Appl.Physiol. 60(2): 385-390, 1986.


    2 mecanisms for afterdrop l.jpg
    2 mecanisms for afterdrop

    • Convection mecanism

      • Return of cold blood from periphery

      • Minimal is any contribution

    • Conduction mecanism

      • Thermal gradient principal

      • Heat flow principal

    Webb, Paul. Afterdrop of body temperature during rewarming: an alternative explanation. J.Appl.Physiol. 60(2): 385-390, 1986.


    Conduction mecanism l.jpg
    Conduction Mecanism

    Environement

    Skin/Tissues

    Blood vessel

    Heat transfer

    Heat transfer


    Afterdrop an alternative explanation l.jpg
    Afterdrop: an alternative explanation

    • Active external rewarming  increase threat of further cooling of the heart…as much as thought before.

    • Correlated by many other papers

    • Savard, G.K., K.E. Cooper, W.L. Veale, and T.J. Malkinson. Peripheral blood flow during rewarming from mild hypothermia in humans. J. Appl. Physiol. 58(1): 4-13, 1985.

    • Romet, Tiit T. Mechanism of afterdrop after cold water immersion. J.Appl.Physiol. 65(4): 1535-1538, 1988.


    The alcatraz san francisco swim study l.jpg
    The Alcatraz/San Francisco Swim Study

    • San Francisco Bay…contest…

    • Swims from Alcatraz Island to shore

    • No wetsuits or protective clothing

    • Water T = 12C (53F)

    • Outside : T = 10C

    • 3 Km

    • 11 subjects for study

    • 23 y.o to 70 y.o (!)

    • Measured T after contest.

    Thomas J. Nuckton and al. Hypothermia and afterdrop following open water swimming: The Alcatrax/San Francisco Swim Study. Am J Emerg Med 2000; 18:703-707.


    Afterdrop conclusion l.jpg
    Afterdrop conclusion

    • Rectal T lags behing esophageal T and is often > than esophageal and pulmonary T.

    • Think about it but you can probably not prevent it.

    • Issue with active external rewarming

    • Other concerns about external rewarming:

      • Acidosis

      • Hypotension


    Management ed issues l.jpg
    Management: ED issues

    Intubation

    • General belief it can induce arythmias

    • Danzl, Multicenter Hypothermia Survey, Annals Emerg Med, Sept.87.

      • Data from 13 ED

      • 428 cases

      • 117 intubation

      • NO arythmias


    Management ed issues66 l.jpg
    Management: ED issues

    Bretylium

    • Recommended for V.fib in hypothermia

    • Removed from new ACLS 2000:

      •  availability and limited supply

      •  occurrence of side effects

  • Still recommend in textbooks (Rosen)

  • Recommended by US Wilderness Emergency Medical Services Institute

  • Based on Dogs studies

  • Good for prophylaxis only


  • Management ed issues67 l.jpg
    Management: ED issues

    Drugs / Shocks

    • NO drugs if T < 30C

      • Not efficacious

      • Not metabolised

    • If > 30C,  intervals between doses

    • If < 30C and failure of 3 shocks


    Management ed issues68 l.jpg
    Management: ED issues

    Drugs / Shocks

    • NO drugs if T < 30C

      • Not efficacious

      • Not metabolised

    • If > 30C,  intervals between doses

    • If < 30C and failure of 3 shocks

    Defer subsequent shock + Rx until T > 30C


    Acls 2000 l.jpg
    ACLS 2000

    The algorithm…


    Conclusion l.jpg
    Conclusion

    • Hypothermia is rare but treatable

    • Good outcome after prolonged arrests

    • Include Hypothermia in your  Dx

    • Include T as a 5th vital sign…

    • Call early to organize CPB if available if patient in cardiac arrest

    • Prevention is still the best…and…


    Play carefully l.jpg
    Play carefully…

    From Journal Le Soleil, february 2001