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Case 1:. 22 y.o. femaleOut with friends celebrating her birthday (February 19th)Dropped off at her front door by friendsFound by her parents in the morning, passed out just inside the screen doorUnable to wake her? call 911. Case 2:. 85 y.o. maleMid-August, during heat waveSon goes to apartmen
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1. Hyperthermia and Hypothermia Back to Basics
April 2011
Dr. J. 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 under normal circumstances
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 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
Major cause of accidental hypothermia
8. Evaporation 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
9. Hypothermia…
10. Definition Core body temperature less than 35oC
Mild: 32.2 - 35oC
Moderate: 28 - 32.2oC
Severe: < 28oC
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
13. Signs and Symptoms
14. Signs and Symptoms, cont’d
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?
Esp. neurologic, cardiovascular, respiratory
17. Diagnositics ECG (always), CXR (most patients)
Other tests 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, LFTs, lipase/amylase, cultures
18. ECG Changes May see J waves
late, terminal upright deflection of QRS complex; best seen in leads V3-V6
Multiple arrhythmias
Heart block
Atrial fibrillation
Ventricular fibrillation
19. ECG Changes, cont’d
20. Management…