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Hyperthermia and Hypothermia

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Title: Hyperthermia and Hypothermia


1
Hyperthermia and Hypothermia
  • Back to Basics
  • April 2008
  • Dr. Jennifer Clow, ER

2
Case 1
  • 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

3
Case 2
  • 85 y.o. male
  • Mid-august, during heat wave
  • Son goes to apartment and finds patient confused
    and lethargic
  • Patient unable to give history

4
Heat Regulation
  • Four mechanisms of heat loss/dissipation
  • Radiation
  • Convection
  • Conduction
  • Evaporation

5
Radiation
  • Physical transfer of heat between the body and
    the environment by electromagnetic waves
  • 65 of heat transfer
  • Modified by insulation (clothing, fat layer),
    cutaneous blood flow

6
Convection
  • 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 chill
    and body motion

7
Conduction
  • 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

8
Evaporation
  • Most important source of cooling under extreme
    heat stress
  • 25 of heat loss in temperate/cool conditions
    may be increased significantly by sweating,
    increased respiratory rate
  • Affected by relative humidity and clothing

9
Hypothermia
10
Definition
  • Core body temperature less than 35oC
  • Mild 34-36oC
  • Moderate 30-34oC
  • Severe lt 30oC

11
Causes
  • Decreased heat production
  • Endocrine, insufficient fuel, neuromuscular
    inactivity
  • Increased heat loss
  • Accidental/immersion hypothermia, vasodilatation,
    skin disorders, iatrogenic
  • Impaired thermoregulation
  • Central (metabolic, drugs, CNS)
  • Peripheral (spinal cord injury, neuropathy,
    diabetes, neuromuscular disorders)

12
Predisposing Factors
TABLE 19-1 Risk Factors for Hypothermia TABLE 19-1 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
13
Signs and Symptoms
TABLE 110-2. Clinical Manifestations of Hypothermia TABLE 110-2. Clinical Manifestations of Hypothermia TABLE 110-2. Clinical Manifestations of Hypothermia TABLE 110-2. 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 (lt 28C) and asystole (lt 20C)
Respiratory Tachypnea, bronchorrhea Hypoventilation (decreased rate and tidal volume), decreased oxygen consumption and CO2 production, loss of cough reflex Pulmonary edema, apnea
14
Signs and Symptoms, contd
TABLE 110-2. Clinical Manifestations of Hypothermia, contd TABLE 110-2. Clinical Manifestations of Hypothermia, contd TABLE 110-2. Clinical Manifestations of Hypothermia, contd TABLE 110-2. Clinical Manifestations of Hypothermia, contd
System Mild Hypothermia Moderate hypothermia Severe Hypothermia
Renal Cold diuresis Cold diuresis Decreased renal perfusion and GFR, oliguria
Hematologic Increased hematocrit and decreased platelet, white blood cell count, coagulopathy, and DIC    
GI Ileus, pancreatitis, gastric stress ulcers, hepatic dysfunction    
Metabolic endocrine Increased metabolic rate, hyperglycemia Decreased metabolic rate, hyper- or hypoglycemia  
Musculoskeletal Increased shivering Decreased shivering (lt 32C, 90F), muscle rigidity Patient appears dead, "pseudo-rigor mortis"
15
History
  • Often from bystanders/medics
  • Circumstances surrounding exposure
  • Where, submersion, ambient temperature?
  • Length of exposure
  • Mental status changes
  • Any predisposing illness acute/chronic?
  • Alcohol/drugs?

16
Physical Exam
  • Vitals
  • Temperature want a core temperature
  • Where do we take it?
  • Signs of other injuries?
  • Can you find the cause of hypothermia?
  • Any focal findings?

17
Diagnositics
  • ECG!!!
  • Will depend on the clinical scenario
  • Any signs of trauma? May need imaging
  • Are you able to take a history?
  • Past medical history?
  • Labs for all
  • CBC, electrolytes, glucose, renal function,
    toxicology, coags, ABGs, cultures

18
Management
19
Interventions
  • Airway need for intubation?
  • Breathing spontaneous respiration?
  • Warmed humidified oxygen either through an ETT,
    or via mask
  • Circulation pulse? BP?
  • Large IVs warmed IV fluids
  • Arrhythmias when do we treat?
  • CPR?

20
Interventions, contd
  • Disability
  • GCS
  • Glucoscan, narcan, thiamine
  • C-spine immobilization prn
  • Exposure
  • Undress, assess for trauma
  • Recover quickly

21
Rewarming
TABLE 192-3 Rewarming Techniques
Passive rewarming Removal from cold environment Insulation, Warm blankets Active external rewarming Warm water immersion Heating blankets set at 40C Radiant heat Forced air Active core rewarming at 40C Inhalation rewarming Heated IV fluids GI tract lavage Bladder lavage Peritoneal lavage Pleural lavage Extracorporeal rewarming
22
Active Rewarming
  • When?
  • Cardiovascular instability
  • Temp less than 32C
  • Concominant illnesses
  • Extremes of age
  • Failure of passive rewarming
  • Active external or Internal?

23
Rewarming - Extracorporeal
TABLE 19-3 Options for Extracorporeal Rewarming TABLE 19-3 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 2-3C/h
Hemodialysis (HD) Circuit single-or dual-vessel cannulation Stabilizes electrolyte or toxicologic abnormalities Exchange cycle volumes 200-500 mL/min ROR 2-3C/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 3-4C/h
Cardiopulmonary bypass (CPB) Circuit full circulatory support with pump and oxygenator Perfusate-temperature gradient (5-10C) Flow rates 2-7 L/min (ave. 3-4) ROR up to 9.5C/h
Note BP, blood pressure CV, central venous ROR, rate of rewarming. Note BP, blood pressure CV, central venous ROR, rate of rewarming.
24
Hyperthermia
25
Definition
  • Core body temperature gt 38oC
  • Spectrum of heat-related illnesses
  • Heat cramps
  • Heat exhaustion
  • Heat stroke

26
Causes
  • Increased heat load
  • Heat absorption from environment
  • Heat stroke (exertional, classic)
  • Metabolic heat
  • Diminished heat dissipation
  • Obesity, anhidrosis, drugs
  • Sepsis

27
Predisposing Factors
TABLE 111-1. Predisposing Factors for Heat Stroke TABLE 111-1. 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
  ß Blockers
28
Causes of Hyperthermia
TABLE 16-1 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
29
Differential Diagnosis
TABLE 193-1 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
30
Signs and Symptoms
  • Heat cramps
  • Cramps in big muscles spasms
  • Normal temperature, mentation
  • Caused by dilutional hyponatremia (hypotonic
    fluid replacement)

31
Signs and Symptoms, contd
  • Heat exhaustion
  • Weakness, dizziness, headache, syncope
  • Nausea, vomiting
  • Temperature 39-41.1oC
  • Normal mentation
  • Profuse sweating

32
Signs and Symptoms, contd
  • Heat Stroke
  • Mortality of 10-20 with current treatment
  • Coma, seizures, confusion
  • No sweating
  • Temperature gt41.1oC
  • Classic triad hyperpyrexia, CNS dysfunction,
    anhidrosis
  • Classic vs. Exertional

33
History
  • Circumstances (as per hypothermia)
  • Exertion?
  • Fluids?
  • Past medical history any acute or chronic
    illnesses that may worsen situation
  • Trauma?

34
Physical Examination
  • Temperature
  • Where do we take it? And how?
  • Vitals!
  • Look for complications or other causes of the
    patients symptoms

35
Diagnostics
  • ECG
  • Imaging guided by history
  • CBC, electrolytes, renal function, LFTs, Ca, Mg,
    PO4, coags
  • Urine myoglobin
  • Pan-cultures

36
Poor prognostic factors
  • Temperature gt 41.1oC
  • AST gt 1000
  • Coma
  • Rhabdomyolysis
  • Renal Failure
  • Hypotension

37
Treatment
  • ABCs!!!
  • Cooling
  • Remove to cool environment!
  • Correct fluid and electrolyte imbalances

38
Treatment
TABLE 193-2 Comparison of Cooling Techniques TABLE 193-2 Comparison of Cooling Techniques TABLE 193-2 Comparison of Cooling Techniques
Technique Advantages Disadvantages
Evaporative   Simple, Readily available Noninvasive Easy patient access Relatively effective Shivering Difficult to maintain monitoring electrodes in position
Immersion Noninvasive Relatively effective   Shivering, Cumbersome Poorly tolerated Logistically difficult to access Difficult to maintain monitoring
Ice packing   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
39
Complications of Heat Stroke
TABLE 193-3 Complications of Heatstroke TABLE 193-3 Complications of Heatstroke TABLE 193-3 Complications of Heatstroke
  Initial Delayed
Vital signs     Hypotension Hypothermia overshoot Hyperthermic rebound      
Muscular   Shivering Rhabdomyolysis    
Neurologic     Delirium Seizures Coma Cerebral edema    
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       Thrombocytopenia Disseminated intravascular coagulation
40
Back to the cases
41
Case 1 Hypothermia
  • What do you want to know?
  • Physical Exam?
  • Labs?
  • Any imaging?
  • How are you going to treat her?

42
Case 2 Hyperthermia
  • What do you want to know?
  • Physical Exam?
  • Labs?
  • Any imaging?
  • How are you going to treat him?
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