HyperthermiaHyperthermia and and HypothermiaHypothermia

Back to BasicsBack to Basics

April 2011April 2011

Dr. J. Clow, ERDr. J. Clow, ER

Case 1:Case 1:

22 y.o. female22 y.o. female Out with friends celebrating her Out with friends celebrating her

birthday (February 19birthday (February 19thth)) Dropped off at her front door by Dropped off at her front door by

friendsfriends Found by her parents in the morning, Found by her parents in the morning,

passed out just inside the screen doorpassed out just inside the screen door Unable to wake her… call 911Unable to wake her… call 911

Case 2:Case 2:

85 y.o. male85 y.o. male Mid-August, during heat waveMid-August, during heat wave Son goes to apartment and finds Son goes to apartment and finds

patient confused and lethargicpatient confused and lethargic Patient unable to give historyPatient unable to give history

Heat RegulationHeat Regulation

Four mechanisms of heat Four mechanisms of heat loss/dissipation:loss/dissipation: RadiationRadiation ConvectionConvection ConductionConduction EvaporationEvaporation

RadiationRadiation

Physical transfer of heat between the Physical transfer of heat between the body and the environment by body and the environment by electromagnetic waveselectromagnetic waves

65% of heat transfer under normal 65% of heat transfer under normal circumstancescircumstances

Modified by insulation (clothing, fat Modified by insulation (clothing, fat layer), cutaneous blood flowlayer), cutaneous blood flow

ConvectionConvection

Energy transfer between the body Energy transfer between the body and a gas or liquidand a gas or liquid

Affected by temperature gradient, Affected by temperature gradient, motion at the interface, and liquidmotion at the interface, and liquid

Not usually a major source for heat Not usually a major source for heat loss or dissipation, but this increases loss or dissipation, but this increases with wind and body motionwith wind and body motion

ConductionConduction

Direct transfer of heat energy between Direct transfer of heat energy between two surfacestwo surfaces

Responsible for only a small proportion Responsible for only a small proportion of heat loss under normal circumstancesof heat loss under normal circumstances

Increases significantly with immersion in Increases significantly with immersion in cold watercold water

Major cause of accidental hypothermiaMajor cause of accidental hypothermia

EvaporationEvaporation

Most important source of cooling under Most important source of cooling under extreme heat stress; important for extreme heat stress; important for hypothermia when in wet environmenthypothermia when in wet environment

25% of heat loss in temperate/cool 25% of heat loss in temperate/cool conditions… may be increased conditions… may be increased significantly by sweating, increased significantly by sweating, increased respiratory raterespiratory rate

Affected by relative humidity and Affected by relative humidity and clothingclothing

Hypothermia…Hypothermia…

DefinitionDefinition

Core body temperature less than Core body temperature less than 3535ooCC Mild: 32.2 - 35Mild: 32.2 - 35ooCC Moderate: 28 - 32.2Moderate: 28 - 32.2ooCC Severe: < 28Severe: < 28ooCC

Causes…Causes… Decreased heat productionDecreased heat production

Endocrine, insufficient fuel, neuromuscular Endocrine, insufficient fuel, neuromuscular inactivityinactivity

Increased heat lossIncreased heat loss Accidental/immersion hypothermia, Accidental/immersion hypothermia,

vasodilatation, skin disorders, iatrogenicvasodilatation, skin disorders, iatrogenic Impaired thermoregulationImpaired thermoregulation

Central (metabolic, drugs, CNS)Central (metabolic, drugs, CNS) Peripheral (spinal cord injury, neuropathy, Peripheral (spinal cord injury, neuropathy,

diabetes, neuromuscular disorders)diabetes, neuromuscular disorders)

Predisposing FactorsPredisposing Factors

Risk Factors for Hypothermia

Age extremes Elderly NeonatesOutdoor exposure Occupational Sports-related Inadequate clothingDrugs and intoxicants Ethanol Phenothiazines Barbiturates Anesthetics Neuromuscular blockers Others

Endocrine-related Hypoglycemia Hypothyroidism Adrenal insufficiency HypopituitarismNeurologic-related Stroke Hypothalamic disorders Parkinson's disease Spinal cord injuryMultisystem Malnutrition Sepsis Shock Hepatic or renal failureBurns and exfoliative dermatologic disordersImmobility or debilitation

Signs and SymptomsSigns and SymptomsClinical Manifestations of Hypothermia

System Mild Hypothermia Moderate Hypothermia Severe Hypothermia

CNS Confusion, slurred speech, impaired judgment, amnesia

Lethargy, hallucinations, loss of pupillary reflex, EEG abnormalities

Loss of cerebrovascular regulation, decline in EEG activity, coma, loss of ocular reflex

CVS Tachycardia, increased cardiac output and systemic vascular resistance

Progressive bradycardia (unresponsive to atropine), decreased cardiac output and BP, atrial and ventricular arrhythmias, J (Osborn) wave on ECG

Decline in BP and cardiac output, ventricular fibrillation (< 28°C) & asystole (< 20°C)

Respiratory Tachypnea, bronchorrhea Hypoventilation (decreased rate and tidal volume), decreased oxygen consumption and CO2

production, loss of cough reflex

Pulmonary edema, apnea

Signs and Symptoms, cont’dSigns and Symptoms, cont’dTABLE 110-2. Clinical Manifestations of Hypothermia, cont’d

System Mild Hypothermia Moderate hypothermia Severe Hypothermia

Renal Cold diuresis Cold diuresis Decreased renal perfusion and GFR, oliguria

Hematologic Increased hematocrit, decreased platelet & white blood cell counts, coagulopathy, DIC

   

GI Ileus, pancreatitis, gastric stress ulcers, hepatic dysfunction

   

Metabolic Increased metabolic rate, hyperglycemia

Decreased metabolic rate, hyper- or hypoglycemia

 

Musculoskeletal Increased shivering Decreased shivering (< 32°C, 90°F), muscle rigidity

Patient appears dead, "pseudo-rigor mortis"

HistoryHistory

Often from bystanders/medicsOften from bystanders/medics Circumstances surrounding exposureCircumstances surrounding exposure

Where, submersion, ambient temperature?Where, submersion, ambient temperature? Length of exposureLength of exposure

Mental status changesMental status changes Any predisposing illness – acute/chronic?Any predisposing illness – acute/chronic? Alcohol/drugs?Alcohol/drugs?

Physical ExamPhysical Exam

Vitals…Vitals… Temperature – want a core temperatureTemperature – want a core temperature

Where do we take it?Where do we take it? Signs of other injuries?Signs of other injuries? Can you find the cause of hypothermia?Can you find the cause of hypothermia? Any focal findings?Any focal findings?

Esp. neurologic, cardiovascular, respiratoryEsp. neurologic, cardiovascular, respiratory

DiagnositicsDiagnositics

ECG (always), CXR (most patients)ECG (always), CXR (most patients) Other tests depend on the clinical scenarioOther tests depend on the clinical scenario

Any signs of trauma? May need imaging…Any signs of trauma? May need imaging… Are you able to take a history?Are you able to take a history? Past medical history?Past medical history?

Labs for all:Labs for all: CBC, electrolytes, glucose, renal function, CBC, electrolytes, glucose, renal function,

toxicology, coags, ABGs, LFTs, lipase/amylase, toxicology, coags, ABGs, LFTs, lipase/amylase, culturescultures

ECG ChangesECG Changes

May see J wavesMay see J waves late, terminal upright deflection of QRS late, terminal upright deflection of QRS

complex; best seen in leads V3-V6complex; best seen in leads V3-V6 Multiple arrhythmiasMultiple arrhythmias

Heart blockHeart block Atrial fibrillationAtrial fibrillation Ventricular fibrillationVentricular fibrillation

ECG Changes, cont’dECG Changes, cont’d

Management…Management…

InterventionsInterventions

Airway: need for intubation?Airway: need for intubation? Breathing: spontaneous respiration?Breathing: spontaneous respiration?

Warmed humidified oxygen – either Warmed humidified oxygen – either through an ETT, or via maskthrough an ETT, or via mask

Circulation: pulse? BP?Circulation: pulse? BP? Large IVs – warmed IV fluidsLarge IVs – warmed IV fluids Arrhythmias – when do we treat?Arrhythmias – when do we treat? CPR?CPR?

Interventions, cont’dInterventions, cont’d

DisabilityDisability GCSGCS Glucoscan, narcan, thiamineGlucoscan, narcan, thiamine C-spine immobilization prnC-spine immobilization prn

ExposureExposure Undress, assess for traumaUndress, assess for trauma Re-cover quicklyRe-cover quickly

RewarmingRewarmingRewarming Techniques

Passive rewarming: Removal from cold environment Insulation, Warm blankets (e.g. Bair hugger)Active external rewarming: Warm water immersion Heating blankets set at 40°C Radiant heat Forced airActive core rewarming at 40°C: Inhalation rewarming Heated IV fluids GI tract lavage Bladder lavage Peritoneal lavage Pleural lavageExtracorporeal rewarming

Active RewarmingActive Rewarming

When?When? Cardiovascular instabilityCardiovascular instability Temp less than 32Temp less than 32ooCC Concominant illnessesConcominant illnesses Extremes of ageExtremes of age Failure of passive rewarmingFailure of passive rewarming

Active external or internal?Active external or internal?

Rewarming - ExtracorporealRewarming - ExtracorporealOptions for Extracorporeal Rewarming

Extracorporeal Rewarming(ECR) Technique Considerations

Venovenous (VV) Circuit — CV catheter to CV or peripheral catheterNo oxygenator/circulatory supportFlow rates 150-400 mL/minROR 2°-3°C/h

Hemodialysis (HD) Circuit — single-or dual-vessel cannulationStabilizes electrolyte or toxicologic abnormalitiesExchange cycle volumes 200-500 mL/minROR 2°-3°C/h

Continuous arteriovenous rewarming (CAVR)

Circuit — percutaneous 8.5 Fr femoral cathetersRequires BP 60 mmHg systolicNo perfusionist/pump/anticoagulationFlow rates 225-375 mL/minROR 3°-4°C/h

Cardiopulmonary bypass (CPB) Circuit — full circulatory support with pump and oxygenatorPerfusate-temperature gradient (5°-10°C)Flow rates 2-7 L/min (ave. 3-4)ROR up to 9.5°C/h

Note: BP, blood pressure; CV, central venous; ROR, rate of rewarming.

Hyperthermia…Hyperthermia…

DefinitionDefinition

Core body temperature > 38Core body temperature > 38ooCC Caused by a failure of thermoregulationCaused by a failure of thermoregulation

Contrast with fever – cause is cytokine Contrast with fever – cause is cytokine activ’nactiv’n

Spectrum of heat-related illnessesSpectrum of heat-related illnesses Heat crampsHeat cramps Heat exhaustionHeat exhaustion Heat strokeHeat stroke

SpectrumSpectrum

Heat crampsHeat cramps Cramps in big muscles – spasmsCramps in big muscles – spasms Normal temperature, mentationNormal temperature, mentation Caused by dilutional hyponatremia Caused by dilutional hyponatremia

(hypotonic fluid replacement)(hypotonic fluid replacement)

Spectrum, cont’dSpectrum, cont’d

Heat exhaustionHeat exhaustion Weakness, dizziness, headache, Weakness, dizziness, headache,

syncopesyncope Nausea, vomitingNausea, vomiting Temperature 39-41.1Temperature 39-41.1ooCC Normal mentationNormal mentation Profuse sweatingProfuse sweating

Spectrum, cont’dSpectrum, cont’d

Heat StrokeHeat Stroke Temperature >41.1Temperature >41.1ooCC Coma, seizures, confusionComa, seizures, confusion No sweatingNo sweating Classic triad: hyperpyrexia, CNS Classic triad: hyperpyrexia, CNS

dysfunction, anhidrosisdysfunction, anhidrosis Mortality of 10-20% Mortality of 10-20% withwith treatment treatment Classic vs. ExertionalClassic vs. Exertional

Spectrum, cont’dSpectrum, cont’d

Heat Stroke:Heat Stroke: Classic (non-exertional):Classic (non-exertional):

Persistent environmental exposurePersistent environmental exposure Impaired thermoregulationImpaired thermoregulation

Exertional:Exertional: Heavy exercise in setting of high Heavy exercise in setting of high

temperature and humiditytemperature and humidity

Causes of HyperthermiaCauses of Hyperthermia

Increased heat loadIncreased heat load Heat absorption from environmentHeat absorption from environment

Heat stroke (exertional, classic)Heat stroke (exertional, classic) Metabolic heatMetabolic heat

Diminished heat dissipationDiminished heat dissipation Obesity, anhidrosis, drugsObesity, anhidrosis, drugs

SepsisSepsis

Predisposing Factors…Predisposing Factors…

Predisposing Factors for Heat Stroke

Increased Heat Production Decreased Heat Loss

Environmental heat stress Environmental heat stress

Exertion Cardiac disease

Fever Peripheral vascular disease

Hypothalamic dysfunction Dehydration

Drugs (sympathomimetics) Anticholinergic drugs

Hyperthyroidism Obesity

  Skin disease

  Ethanol

  β Blockers

Causes of Hyperthermia…Causes of Hyperthermia…Causes of Hyperthermia Syndromes

HEAT STROKEExertional: Exercise in higher-than-normal heat and/or humidityNonexertional: Anticholinergics, including antihistamines; antiparkinsonian drugs; diuretics; phenothiazines

DRUG-INDUCED HYPERTHERMIAAmphetamines, cocaine, phencyclidine (PCP), methylenedioxymethamphetamine (MDMA; "ecstasy"), lysergic

acid diethylamide (LSD), salicylates, lithium, anticholinergics, sympathomimetics

NEUROLEPTIC MALIGNANT SYNDROMEPhenothiazines; butyrophenones, including haloperidol and bromperidol; fluoxetine; loxapine; tricyclic

dibenzodiazepines; metoclopramide; domperidone; thiothixene; molindone; withdrawal of dopaminergic agents

SEROTONIN SYNDROMESelective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors (MAOIs), tricyclic

antidepressants

MALIGNANT HYPERTHERMIAInhalational anesthetics, succinylcholine

ENDOCRINOPATHYThyrotoxicosis, pheochromocytoma

CENTRAL NERVOUS SYSTEM DAMAGECerebral hemorrhage, status epilepticus, hypothalamic injury

Differential DiagnosisDifferential Diagnosis

Differential Diagnosis of Heatstroke

Drug toxicity: anticholinergic toxicity, stimulant toxicity (phencyclidine, cocaine, amphetamines, ephedrine), salicylate toxicity

Drug withdrawal syndrome: ethanol withdrawalSerotonin syndromeNeuroleptic malignant syndromeGeneralized infections: bacterial sepsis, malaria, typhoid fever, tetanusCentral nervous system infections: meningitis, encephalitis, brain abscessEndocrine derangements: diabetic ketoacidosis, thyroid stormNeurologic: status epilepticus, cerebral hemorrhage

HistoryHistory

Circumstances (as per hypothermia)Circumstances (as per hypothermia) Exertion?Exertion? Fluids?Fluids? Past medical history – any acute or Past medical history – any acute or

chronic illnesses that may worsen chronic illnesses that may worsen situationsituation

Medications/DrugsMedications/Drugs Trauma?Trauma?

Physical ExaminationPhysical Examination

TemperatureTemperature Where do we take it? And how?Where do we take it? And how?

Vitals!Vitals! Look for complications or other Look for complications or other

causes of the patients symptomscauses of the patients symptoms Respiratory, cardiac, neurologic Respiratory, cardiac, neurologic

examinationexamination Signs of bleedingSigns of bleeding

DiagnosticsDiagnostics

ECG (all), CXR (most)ECG (all), CXR (most) Imaging guided by historyImaging guided by history CBC, electrolytes, renal function, CBC, electrolytes, renal function,

LFTs, Ca, Mg, PO4, coags, CKLFTs, Ca, Mg, PO4, coags, CK Urine – myoglobinUrine – myoglobin Pan-culturesPan-cultures

Poor prognostic factorsPoor prognostic factors

Temperature > 41.1Temperature > 41.1ooCC AST > 1000AST > 1000 ComaComa RhabdomyolysisRhabdomyolysis Renal FailureRenal Failure HypotensionHypotension

TreatmentTreatment

ABC’s!!!ABC’s!!! Remove to cool environment!Remove to cool environment! Active coolingActive cooling Correct fluid and electrolyte Correct fluid and electrolyte

imbalancesimbalances Supportive careSupportive care

TreatmentTreatmentComparison of Cooling Techniques

Technique Advantages Disadvantages

Evaporative(i.e. wet the patient’s gown,

sheets then use fan) 

Simple, Readily availableNoninvasiveEasy patient accessRelatively effective

ShiveringDifficult to maintain monitoring electrodes in position

Immersion(in cold/ice water)

NoninvasiveRelatively effective 

Shivering, CumbersomePoorly toleratedLogistically difficult to accessDifficult to maintain monitoring

Ice packing (cover w/ ice) 

NoninvasiveReadily available

ShiveringPoorly tolerated

Strategic ice packs 

NoninvasiveReadily availableCombined with other techniques

ShiveringPoorly toleratedMedium efficiency

Cold gastric lavage   

Generally available    

InvasiveLabor intensivePotential for water intoxicationMay require airway protectionLimited human experience

Cold peritoneal lavage 

Theoretically beneficial InvasiveLimited human experience

Complications of Heat Complications of Heat StrokeStroke

Complications of Heatstroke

  Immediate Delayed

Vital signs  

HypotensionHypothermia overshootHyperthermic rebound

   

Muscular 

ShiveringRhabdomyolysis

  

Neurologic  

DeliriumSeizuresComa

Cerebral edema  

Cardiac Heart failure  

Pulmonary Pulmonary edema Acute respiratory distress syndrome

Renal Oliguria Renal failure

Gastrointestinal 

Diarrhea 

Hepatic necrosisMucosal gastrointestinal hemorrhage

Metabolic  

HypokalemiaHypernatremia 

HyperkalemiaHypocalcemiaHyperuricemia

Hematologic 

  

ThrombocytopeniaDisseminated intravascular coagulation

Back to the cases…Back to the cases…

Case 1: HypothermiaCase 1: Hypothermia

What do you want to know?What do you want to know? Physical Exam?Physical Exam? Labs?Labs? Any imaging?Any imaging?

How are you going to treat her?How are you going to treat her?

Case 2: HyperthermiaCase 2: Hyperthermia

What do you want to know?What do you want to know? Physical Exam?Physical Exam? Labs?Labs? Any imaging?Any imaging?

How are you going to treat him?How are you going to treat him?