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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?