Transcript Basics Thermias Dr Chow 2011

Hyperthermia and
Hypothermia
Back to Basics
April 2011
Dr. J. Clow, ER
Case 1:
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22 y.o. female
Out with friends celebrating her birthday
(February 19th)
Dropped off at her front door by friends
Found by her parents in the morning,
passed out just inside the screen door
Unable to wake her… call 911
Case 2:
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85 y.o. male
Mid-August, during heat wave
Son goes to apartment and finds patient
confused and lethargic
Patient unable to give history
Heat Regulation
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Four mechanisms of heat loss/dissipation:
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Radiation
Convection
Conduction
Evaporation
Radiation
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Physical transfer of heat between the
body and the environment by
electromagnetic waves
65% of heat transfer under normal
circumstances
Modified by insulation (clothing, fat layer),
cutaneous blood flow
Convection
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Energy transfer between the body and a
gas or liquid
Affected by temperature gradient, motion
at the interface, and liquid
Not usually a major source for heat loss or
dissipation, but this increases with wind
and body motion
Conduction
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Direct transfer of heat energy between
two surfaces
Responsible for only a small proportion of
heat loss under normal circumstances
Increases significantly with immersion in
cold water
Major cause of accidental hypothermia
Evaporation
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Most important source of cooling under
extreme heat stress; important for
hypothermia when in wet environment
25% of heat loss in temperate/cool
conditions… may be increased significantly
by sweating, increased respiratory rate
Affected by relative humidity and clothing
Hypothermia…
Definition
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Core body temperature less than 35oC
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Mild: 32.2 - 35oC
Moderate: 28 - 32.2oC
Severe: < 28oC
Causes…
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Decreased heat production
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Increased heat loss
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Endocrine, insufficient fuel, neuromuscular inactivity
Accidental/immersion hypothermia, vasodilatation,
skin disorders, iatrogenic
Impaired thermoregulation
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Central (metabolic, drugs, CNS)
Peripheral (spinal cord injury, neuropathy, diabetes,
neuromuscular disorders)
Predisposing Factors
Risk Factors for Hypothermia
Age extremes
Elderly
Neonates
Outdoor exposure
Occupational
Sports-related
Inadequate clothing
Drugs and intoxicants
Ethanol
Phenothiazines
Barbiturates
Anesthetics
Neuromuscular blockers
Others
Endocrine-related
Hypoglycemia
Hypothyroidism
Adrenal insufficiency
Hypopituitarism
Neurologic-related
Stroke
Hypothalamic disorders
Parkinson's disease
Spinal cord injury
Multisystem
Malnutrition
Sepsis
Shock
Hepatic or renal failure
Burns and exfoliative dermatologic disorders
Immobility or debilitation
Signs and Symptoms
Clinical 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’d
TABLE 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"
History
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Often from bystanders/medics
Circumstances surrounding exposure
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Where, submersion, ambient temperature?
Length of exposure
Mental status changes
Any predisposing illness – acute/chronic?
Alcohol/drugs?
Physical Exam
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Vitals…
Temperature – want a core temperature
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Where do we take it?
Signs of other injuries?
Can you find the cause of hypothermia?
Any focal findings?
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Esp. neurologic, cardiovascular, respiratory
Diagnositics
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ECG (always), CXR (most patients)
Other tests depend on the clinical scenario
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Any signs of trauma? May need imaging…
Are you able to take a history?
Past medical history?
Labs for all:
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CBC, electrolytes, glucose, renal function, toxicology,
coags, ABGs, LFTs, lipase/amylase, cultures
ECG Changes
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May see J waves
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late, terminal upright deflection of QRS
complex; best seen in leads V3-V6
Multiple arrhythmias
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Heart block
Atrial fibrillation
Ventricular fibrillation
ECG Changes, cont’d
Management…
Interventions
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Airway: need for intubation?
Breathing: spontaneous respiration?
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Warmed humidified oxygen – either through
an ETT, or via mask
Circulation: pulse? BP?
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Large IVs – warmed IV fluids
Arrhythmias – when do we treat?
CPR?
Interventions, cont’d
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Disability
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GCS
Glucoscan, narcan, thiamine
C-spine immobilization prn
Exposure
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Undress, assess for trauma
Re-cover quickly
Rewarming
Rewarming 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 air
Active core rewarming at 40°C:
Inhalation rewarming
Heated IV fluids
GI tract lavage
Bladder lavage
Peritoneal lavage
Pleural lavage
Extracorporeal rewarming
Active Rewarming
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When?
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Cardiovascular instability
Temp less than 32oC
Concominant illnesses
Extremes of age
Failure of passive rewarming
Active external or internal?
Rewarming - Extracorporeal
Options for Extracorporeal Rewarming
Extracorporeal Rewarming
(ECR) Technique
Considerations
Venovenous (VV)
Circuit — CV catheter to CV or peripheral catheter
No oxygenator/circulatory support
Flow rates 150-400 mL/min
ROR 2°-3°C/h
Hemodialysis (HD)
Circuit — single-or dual-vessel cannulation
Stabilizes electrolyte or toxicologic abnormalities
Exchange cycle volumes 200-500 mL/min
ROR 2°-3°C/h
Continuous arteriovenous rewarming
(CAVR)
Circuit — percutaneous 8.5 Fr femoral catheters
Requires BP 60 mmHg systolic
No perfusionist/pump/anticoagulation
Flow rates 225-375 mL/min
ROR 3°-4°C/h
Cardiopulmonary bypass (CPB)
Circuit — full circulatory support with pump and oxygenator
Perfusate-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…
Definition
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Core body temperature > 38oC
Caused by a failure of thermoregulation
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Contrast with fever – cause is cytokine activ’n
Spectrum of heat-related illnesses
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Heat cramps
Heat exhaustion
Heat stroke
Spectrum
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Heat cramps
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Cramps in big muscles – spasms
Normal temperature, mentation
Caused by dilutional hyponatremia (hypotonic
fluid replacement)
Spectrum, cont’d
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Heat exhaustion
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Weakness, dizziness, headache, syncope
Nausea, vomiting
Temperature 39-41.1oC
Normal mentation
Profuse sweating
Spectrum, cont’d
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Heat Stroke
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Temperature >41.1oC
Coma, seizures, confusion
No sweating
Classic triad: hyperpyrexia, CNS dysfunction,
anhidrosis
Mortality of 10-20% with treatment
Classic vs. Exertional
Spectrum, cont’d
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Heat Stroke:
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Classic (non-exertional):
Persistent environmental exposure
 Impaired thermoregulation
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Exertional:
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Heavy exercise in setting of high temperature and
humidity
Causes of Hyperthermia
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Increased heat load
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Heat absorption from environment
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Metabolic heat
Diminished heat dissipation
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Heat stroke (exertional, classic)
Obesity, anhidrosis, drugs
Sepsis
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 Syndromes
HEAT STROKE
Exertional: Exercise in higher-than-normal heat and/or humidity
Nonexertional: Anticholinergics, including antihistamines; antiparkinsonian drugs; diuretics; phenothiazines
DRUG-INDUCED HYPERTHERMIA
Amphetamines, cocaine, phencyclidine (PCP), methylenedioxymethamphetamine (MDMA; "ecstasy"), lysergic
acid diethylamide (LSD), salicylates, lithium, anticholinergics, sympathomimetics
NEUROLEPTIC MALIGNANT SYNDROME
Phenothiazines; butyrophenones, including haloperidol and bromperidol; fluoxetine; loxapine; tricyclic
dibenzodiazepines; metoclopramide; domperidone; thiothixene; molindone; withdrawal of dopaminergic
agents
SEROTONIN SYNDROME
Selective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors (MAOIs), tricyclic
antidepressants
MALIGNANT HYPERTHERMIA
Inhalational anesthetics, succinylcholine
ENDOCRINOPATHY
Thyrotoxicosis, pheochromocytoma
CENTRAL NERVOUS SYSTEM DAMAGE
Cerebral hemorrhage, status epilepticus, hypothalamic injury
Differential Diagnosis
Differential Diagnosis of Heatstroke
Drug toxicity: anticholinergic toxicity, stimulant toxicity (phencyclidine, cocaine,
amphetamines, ephedrine), salicylate toxicity
Drug withdrawal syndrome: ethanol withdrawal
Serotonin syndrome
Neuroleptic malignant syndrome
Generalized infections: bacterial sepsis, malaria, typhoid fever, tetanus
Central nervous system infections: meningitis, encephalitis, brain abscess
Endocrine derangements: diabetic ketoacidosis, thyroid storm
Neurologic: status epilepticus, cerebral hemorrhage
History
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Circumstances (as per hypothermia)
Exertion?
Fluids?
Past medical history – any acute or
chronic illnesses that may worsen situation
Medications/Drugs
Trauma?
Physical Examination
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Temperature
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Where do we take it? And how?
Vitals!
Look for complications or other causes of
the patients symptoms
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Respiratory, cardiac, neurologic examination
Signs of bleeding
Diagnostics
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ECG (all), CXR (most)
Imaging guided by history
CBC, electrolytes, renal function, LFTs, Ca,
Mg, PO4, coags, CK
Urine – myoglobin
Pan-cultures
Poor prognostic factors
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Temperature > 41.1oC
AST > 1000
Coma
Rhabdomyolysis
Renal Failure
Hypotension
Treatment
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ABC’s!!!
Remove to cool environment!
Active cooling
Correct fluid and electrolyte imbalances
Supportive care
Treatment
Comparison of Cooling Techniques
Technique
Advantages
Disadvantages
Evaporative
(i.e. wet the patient’s gown,
sheets then use fan)
Simple, Readily available
Noninvasive
Easy patient access
Relatively effective
Shivering
Difficult to maintain monitoring electrodes in position
Immersion
(in cold/ice water)
Noninvasive
Relatively effective
Shivering, Cumbersome
Poorly tolerated
Logistically difficult to access
Difficult to maintain monitoring
Ice packing (cover w/ ice)
Noninvasive
Readily available
Shivering
Poorly tolerated
Strategic ice packs
Noninvasive
Readily available
Combined with other techniques
Shivering
Poorly tolerated
Medium efficiency
Cold gastric lavage
Generally available
Invasive
Labor intensive
Potential for water intoxication
May require airway protection
Limited human experience
Cold peritoneal lavage
Theoretically beneficial
Invasive
Limited human experience
Complications of Heat Stroke
Complications of Heatstroke
Immediate
Delayed
Vital signs
Hypotension
Hypothermia overshoot
Hyperthermic rebound
Muscular
Shivering
Rhabdomyolysis
Neurologic
Delirium
Seizures
Coma
Cardiac
Heart failure
Pulmonary
Pulmonary edema
Acute respiratory distress syndrome
Renal
Oliguria
Renal failure
Gastrointestinal
Diarrhea
Hepatic necrosis
Mucosal gastrointestinal hemorrhage
Metabolic
Hypokalemia
Hypernatremia
Hyperkalemia
Hypocalcemia
Hyperuricemia
Hematologic
Cerebral edema
Thrombocytopenia
Disseminated intravascular coagulation
Back to the cases…
Case 1: Hypothermia
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What do you want to know?
Physical Exam?
Labs?
Any imaging?
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How are you going to treat her?
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Case 2: Hyperthermia
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What do you want to know?
Physical Exam?
Labs?
Any imaging?
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How are you going to treat him?
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