Hypothermia

Dr Noora

1. HypothermiaHypothermia
Noora Al-Sukaiti
R2

2. Outline:Outline:
•DefinitionDefinition
•PathophysiologyPathophysiology
•Predisposing factorsPredisposing factors
•Clinical featuresClinical features
•Diagnostic strategiesDiagnostic strategies
•ManagementManagement
•Disposition Disposition

3. What is hypothermia?What is hypothermia?
•Core temp <35 CCore temp <35 C
•Mild 32-35Mild 32-35
•Mod 32-27Mod 32-27
•Severe <27 Severe <27

4. •Basal heat production (40-60kcal/m2 of BSA) Basal heat production (40-60kcal/m2 of BSA)
•inc. with food, mus. activity, fever and acute cold inc. with food, mus. activity, fever and acute cold
exposure exposure
•Max production lasts for a few hrs (b/c of fatigue Max production lasts for a few hrs (b/c of fatigue
and glycogen depletion)and glycogen depletion)

6. Mechanisms of normal heat loss:Mechanisms of normal heat loss:
•RadiationRadiation (65%) most important (65%) most important
by electromagnetic wavesby electromagnetic waves
•EvaporationEvaporation (25%): liquid to a gas (25%): liquid to a gas
0.56 kcal/ml of evaporated H2O0.56 kcal/ml of evaporated H2O
•ConvectionConvection (10-15%) heat loss to air and vapor (10-15%) heat loss to air and vapor
circulating arnd the bodycirculating arnd the body
wind temp and velocitywind temp and velocity
•ConductionConduction (2+ %): direct contact (2+ %): direct contact
important with immersion important with immersion

7. •37-32 C : 37-32 C : vasoconstriction, shivering and non- vasoconstriction, shivering and non-
shivering endocrine thermogenesisshivering endocrine thermogenesis
•32-24 C : 32-24 C : prog. reduction in basal met rate (NO prog. reduction in basal met rate (NO
shivering)shivering)
•<24 C : <24 C : autonomic and endocrine mech. inactive autonomic and endocrine mech. inactive

8. Which of the following cardiac findings Which of the following cardiac findings
is expected in hypothermia:is expected in hypothermia:
2.QT interval prolongation
3.Sinus bradycardia
4.Atrial fibrilation
5.J waves
6.All of the above

9. IdentifyIdentify

Hypothermic J wavesHypothermic J waves

10. J waves on ECG (false):J waves on ECG (false):
1.1.Potentially diagnostic of hypothermiaPotentially diagnostic of hypothermia
2.2.size decreases with temperature size decreases with temperature
depressiondepression
3.3.appear at <32 C at junction of QRS and ST appear at <32 C at junction of QRS and ST
segmentsegment
4.4.DDx local cardiac ischemia, sepsis or CNS DDx local cardiac ischemia, sepsis or CNS
lesionslesions
5.5.Can occur in young normothermic pts Can occur in young normothermic pts

12. CVS and hypothermia (false):CVS and hypothermia (false):
1.1.A Fib occurs at <32C and usually converts A Fib occurs at <32C and usually converts
spontaneously during rewarmingspontaneously during rewarming
2.2.Asystole and VF occur at <25 C Asystole and VF occur at <25 C
3.3.Myocardium is more sensitive to cold than Myocardium is more sensitive to cold than
conduction systemconduction system
4.4.Core T afterdrop is a decline in core T after Core T afterdrop is a decline in core T after
removal from cold environmentremoval from cold environment
5.5.Bradycardia is refractory to atropine Bradycardia is refractory to atropine

13. Other changes:Other changes:
•CNS:CNS:
Progressive dep. >>> silent EEG at 20 CProgressive dep. >>> silent EEG at 20 C
Loss of autoregulation <25 CLoss of autoregulation <25 C
•Renal:Renal:
•Hypothermia: ↓ renal bld flow Hypothermia: ↓ renal bld flow  secrete lg secrete lg
amounts of dilute urine (cold diuresis)amounts of dilute urine (cold diuresis)
•Periph vasocons Periph vasocons  relative central relative central
hypervolemia hypervolemia  cold diuresis cold diuresis
•EtOH doubles ↑ in urine volumeEtOH doubles ↑ in urine volume

14. •RS : RS :
•Initial ↑in RR then ↓ RR proportional to ↓ Initial ↑in RR then ↓ RR proportional to ↓
metabolism metabolism
•CO2 retention & RS acidosis in sev. CO2 retention & RS acidosis in sev.
hypothermia.hypothermia.
•Bronchorrhea, ↓ciliary motility and Bronchorrhea, ↓ciliary motility and
noncardiogenic pulm edemanoncardiogenic pulm edema

15. Factors predisposing to hypothermiaFactors predisposing to hypothermia
(mention 3 main)(mention 3 main)
•Dec heat Dec heat
productionproduction
•EndocrineEndocrine
•Insufficient fuelInsufficient fuel
•NeuromuscularNeuromuscular
•IneffeciencyIneffeciency
•Inc heat lossInc heat loss
•EnvironmentEnvironment
•VasodilationVasodilation
•erythrodermaserythrodermas
•Impaired Impaired
thermoregulationthermoregulation
•Periph.Periph.
•centralcentral
•OthersOthers
•SepsisSepsis
•TraumaTrauma
•CarcinomasCarcinomas
•Etc…Etc…

16. Why old people are more at risk for Why old people are more at risk for
hypothermia?hypothermia?
•Dec ability to sense coldDec ability to sense cold
•Poor adaptive and behavioral responsesPoor adaptive and behavioral responses
•Dec glycogen stores for shiveringDec glycogen stores for shivering
•Dec muscle mass for shiveringDec muscle mass for shivering
•Poor glucose usePoor glucose use
•Autonomic dysfunction- poor vasoconstrictive Autonomic dysfunction- poor vasoconstrictive
abilityability
•Co morbid illnessCo morbid illness
•Peripheral vascular diseasePeripheral vascular disease
•CNS dysfunctionCNS dysfunction
•Cardiac disease Cardiac disease

17. Ethanol with hypothermia (false):Ethanol with hypothermia (false):
1.1.Interacts with every neurotransmitter in Interacts with every neurotransmitter in
brainbrain
2.2.Metabolized faster in hypothermic patientsMetabolized faster in hypothermic patients
3.3.Possible direct damage to hypothalamusPossible direct damage to hypothalamus
4.4.Peripheral vasodilationPeripheral vasodilation
5.5.Impaired cognition and immobilityImpaired cognition and immobility
6.6.Hypoglycemia and/or malnutritionHypoglycemia and/or malnutrition

18. Clinical FeaturesClinical Features
•Mild hypothermiaMild hypothermia: vague sxs (e.g. hunger, : vague sxs (e.g. hunger,
nausea, confusion, dizziness, chills, pruritis and nausea, confusion, dizziness, chills, pruritis and
SOB)SOB)
•Paradoxical undressingParadoxical undressing
•Progressive Progressive ↓ in LOC↓ in LOC
•<22 : unreactive pupils (↓ perfusion)<22 : unreactive pupils (↓ perfusion)
•Hyperreflexia till 32 C >>> hypo >>> absent at Hyperreflexia till 32 C >>> hypo >>> absent at
26C26C
•Q : … is last reflex to disappear and first to Q : … is last reflex to disappear and first to
reappear?reappear?
Knee jerkKnee jerk

19. Name T:Name T:
•Maximum shiveringMaximum shivering
•Extinguish shiveringExtinguish shivering
•A fibA fib
•V fibV fib
•Dilated pupilsDilated pupils
•No reflex/responseNo reflex/response
•AtaxiaAtaxia
35 C35 C
31 C31 C
30 C30 C
26 C26 C
29 C29 C
26 C26 C
33 C33 C

20. 56 yrs old man is brought in by the police after he 56 yrs old man is brought in by the police after he
was found under a bridge in a winter night. His was found under a bridge in a winter night. His
core T is 30.core T is 30.
which of the following findings is likely to be seenwhich of the following findings is likely to be seen::
2.2.AnemiaAnemia
3.3.Pinpoint pupilsPinpoint pupils
4.4.ShiveringShivering
5.5.TachypneaTachypnea
6.6.Urinary diuresisUrinary diuresis

21. Which of the following physiologic changes is Which of the following physiologic changes is
expected in hypothermic pt:expected in hypothermic pt:
•HemoconcentrationHemoconcentration
•HypoglycemiaHypoglycemia
•Metabolic alkalosisMetabolic alkalosis
•OliguriaOliguria
•SeizuresSeizures

22. Lab facts;Lab facts;
•Normally; PCO2 inc 10 mmHg, pH dec 0.08 unitsNormally; PCO2 inc 10 mmHg, pH dec 0.08 units
•pH reduction DOUBLES at 28 CpH reduction DOUBLES at 28 C
•Hematocrit inc 2% for every 1C fallHematocrit inc 2% for every 1C fall
•Persistent hyperglycemia with rewarming,, DKA Persistent hyperglycemia with rewarming,, DKA
or hrgic pancreatitisor hrgic pancreatitis
•Rewarming is the only effective treatment for Rewarming is the only effective treatment for
coagulopathycoagulopathy

23. Hypothermia management (false)Hypothermia management (false)
1.1.Goals of pre-hospital care are to rescue, examine, Goals of pre-hospital care are to rescue, examine,
insulate and rapidly transportinsulate and rapidly transport
2.2.Rectal T is the most practical for core T evaluation Rectal T is the most practical for core T evaluation
and should be inserted to 15 cmand should be inserted to 15 cm
3.3.ET intubation is necessary unless pt is alert with ET intubation is necessary unless pt is alert with
intact protective reflexesintact protective reflexes
4.4.NGT is indicated in mod-sev hypothermia after NGT is indicated in mod-sev hypothermia after
intubationintubation
5.5.Cardiac monitoring is better by central venous Cardiac monitoring is better by central venous
pressure catheterpressure catheter

24. Volume resuscitation in hypothermiaVolume resuscitation in hypothermia
(false):(false):
1.1.Rapid volume expansion is criticalRapid volume expansion is critical
2.2.Adults should receive 250-500ml fluid Adults should receive 250-500ml fluid
challenge of heated 5% dex in NSchallenge of heated 5% dex in NS
3.3.IV fluids should be heated to 40-42 CIV fluids should be heated to 40-42 C
4.4.Microwaving is an option for heating IVFMicrowaving is an option for heating IVF
5.5.IVF should not be shaken before IVF should not be shaken before
administration administration

25. Withhold CPR in hypothermia Withhold CPR in hypothermia
(false):(false):
•Pt with tissue decomposition, rigor mortis, Pt with tissue decomposition, rigor mortis,
dependent lividity and fixed dilated pupilsdependent lividity and fixed dilated pupils
•Obvious lethal injuriesObvious lethal injuries
•Impossible chest wall depressionImpossible chest wall depression
•Signs of life are presentSigns of life are present
•Rescuers are in dangerRescuers are in danger

26. Pharmacology and hypothermia Pharmacology and hypothermia
(false):(false):
2.2.Intramuscular and oral medications should be Intramuscular and oral medications should be
avoidedavoided
3.3.Epineph., dopamine and other vasocnstricors Epineph., dopamine and other vasocnstricors
should be avoidedshould be avoided
4.4.Most hypothermia-induced dysrhythmias Most hypothermia-induced dysrhythmias
convert spontaneously during rewarmingconvert spontaneously during rewarming
5.5.Defibrillation attempts are usually Defibrillation attempts are usually
unsuccessful until the core T is above 28-30 Cunsuccessful until the core T is above 28-30 C
6.6.At any T, 3 defibrillation attempts should be At any T, 3 defibrillation attempts should be
initiatedinitiated

27. Rewarming
•PassivePassive external rewarming external rewarming
patient rewarms on their own, using endogenous heat patient rewarms on their own, using endogenous heat
production mechanismsproduction mechanisms
•ActiveActive rewarming: rewarming:
•Active Active externalexternal rewarming: application of rewarming: application of
exogenous heat to the body externallyexogenous heat to the body externally
•Active Active corecore rewarming rewarming
»Airway rewarmingAirway rewarming
»Peritoneal dialysisPeritoneal dialysis
»Heated irrigationHeated irrigation
»DiathermyDiathermy
»Extracorporeal blood rewarmingExtracorporeal blood rewarming

28. Active ext. rewarming (false)Active ext. rewarming (false)
1.1.Indications are controversial due to the risks of Indications are controversial due to the risks of
shock and afterdropshock and afterdrop
2.2.Optimal candidates are young previously healthy Optimal candidates are young previously healthy
people in whom there are minimal circulatory people in whom there are minimal circulatory
changeschanges
3.3.Heat packs, water bottles and immersion baths of Heat packs, water bottles and immersion baths of
40 C are options40 C are options
4.4.Forced-air warming system is currently most Forced-air warming system is currently most
practical in EDpractical in ED
5.5.Heat sources should be applied to thorax and Heat sources should be applied to thorax and
extremitiesextremities

30. Active core rewarming (true)Active core rewarming (true)
1.1.Airway rewarming is not indicated in all mod or Airway rewarming is not indicated in all mod or
severe hypothermiasevere hypothermia
2.2.Peritoneal dialysis delivers heated dialysate at Peritoneal dialysis delivers heated dialysate at
<40 C to the peritoneal cavity<40 C to the peritoneal cavity
3.3.Peritoneal dialysis can exacerbate preexisting Peritoneal dialysis can exacerbate preexisting
hyperkalemiahyperkalemia
4.4.Mediastinal irrigation and direct myocardial Mediastinal irrigation and direct myocardial
lavage should only be considered in pts lavage should only be considered in pts
without spontaneous perfusionwithout spontaneous perfusion
5.5.Extracorporial blood rewarming should not be Extracorporial blood rewarming should not be
attempted in hypothermic cardiac arrestattempted in hypothermic cardiac arrest

31. Active internal rewarmingActive internal rewarming
•Airway rewarmingAirway rewarming
–Indicated in all moderate to sever Indicated in all moderate to sever
hypotherm,, non invasivehypotherm,, non invasive
–Gas should be 40-42 C and humidifiedGas should be 40-42 C and humidified
–Reduces bronchorrheaReduces bronchorrhea
–Rewarming rate of 1 to 2.5 C/hrRewarming rate of 1 to 2.5 C/hr

32. Air inhalation rewarmingAir inhalation rewarming

33. •Extracorporeal rewarmingExtracorporeal rewarming
–Only in extreme situationsOnly in extreme situations
–Indications: Arrest, No response to other Indications: Arrest, No response to other
methods, frozen extremities, sever electrolyte methods, frozen extremities, sever electrolyte
abnormalities and rhabdomyolysisabnormalities and rhabdomyolysis
–Rewarming rate of 1-2 C every five minutes!Rewarming rate of 1-2 C every five minutes!
•DiathermyDiathermy
–Transmission of heat by conversion of energyTransmission of heat by conversion of energy
–Use low frequency microwave radiationUse low frequency microwave radiation
–Contraindication- frostbite, burns, metallic Contraindication- frostbite, burns, metallic
implants, edemaimplants, edema

34. Indications for Active RewarmingIndications for Active Rewarming
(list 4)(list 4)
•Cardiovascular instability Cardiovascular instability
•Moderate or severe hypothermia (<32.2° C) Moderate or severe hypothermia (<32.2° C)
•Inadequate rate or failure to rewarmInadequate rate or failure to rewarm
• Endocrinologic insufficiency, Endocrinologic insufficiency, ↓ glycogen ↓ glycogen
stores stores
•Traumatic or toxicologic periph vasodilatat’n Traumatic or toxicologic periph vasodilatat’n
•Sec hypothermia impairing thermoregulationSec hypothermia impairing thermoregulation

36. Disposition:Disposition:
•May D/C pts with mild accidental primary May D/C pts with mild accidental primary
hypothermia (>32 C)hypothermia (>32 C)
•admit anyone elseadmit anyone else

•Always r/o underlying medical diseases as Always r/o underlying medical diseases as
causes of hypothermiacauses of hypothermia

37. Outcomes
•Predictors of outcomePredictors of outcome
•prehospital arrestprehospital arrest
•low/absent BPlow/absent BP
•elevated BUNelevated BUN
•need for intubation/NGT in ED.need for intubation/NGT in ED.
•Bad prognostic indicatorBad prognostic indicator
1.1.intravascular thrombosis (fibrinogen <50)intravascular thrombosis (fibrinogen <50)
2.2.cell lysis (K>10)cell lysis (K>10)
3.3.ammonia (>250) ammonia (>250)
(not prospectively validated!)(not prospectively validated!)

38. Thank you!Thank you!