1. Hyperthermia and Hypothermia

2. Heat Regulation Four mechanisms of heat loss/dissipation: –Radiation –Convection –Conduction –Evaporation

3. 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

4. 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

5. 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

6. 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

7. Hypothermia…

8. Definition Core body temperature less than 35 o C –Mild: 34-36 o C –Moderate: 30-34 o C –Severe: < 30 o C

9. 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)

10. 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

11. Signs and Symptoms Clinical Manifestations of Hypothermia SystemMild HypothermiaModerate HypothermiaSevere Hypothermia CNSConfusion, 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 CVSTachycardia, 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) and asystole (< 20°C) RespiratoryTachypnea, bronchorrheaHypoventilation (decreased rate and tidal volume), decreased oxygen consumption and CO 2 production, loss of cough reflex Pulmonary edema, apnea

12. Signs and Symptoms, cont’d Clinical Manifestations of Hypothermia, cont’d SystemMild HypothermiaModerate hypothermiaSevere Hypothermia RenalCold diuresis Decreased renal perfusion and GFR, oliguria HematologicIncreased hematocrit and decreased platelet, white blood cell count, coagulopathy, and DIC GIIleus, pancreatitis, gastric stress ulcers, hepatic dysfunction Metabolic endocrine Increased metabolic rate, hyperglycemia Decreased metabolic rate, hyper- or hypoglycemia MusculoskeletalIncreased shiveringDecreased shivering (< 32°C, 90°F), muscle rigidity Patient appears dead, "pseudo-rigor mortis"

13. 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?

14. Diagnositics ECG!!! Will depend on the clinical scenario Labs for all: –CBC, electrolytes, glucose, renal function, toxicology, cultures

15. Interventions Airway: need for intubation? Breathing: spontaneous respiration? –Warmed humidified oxygen –Circulation: pulse? BP? –Large IVs – warmed IV fluids –Arrhythmias – when do we treat? –CPR?

16. Interventions, cont’d Disability –GCS –C-spine immobilization –Exposure –Undress, assess for trauma –Recover quickly

17. Hyperthermia…

18. Definition Core body temperature > 38 o C Spectrum of heat-related illnesses –Heat cramps –Heat exhaustion –Heat stroke

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

20. Predisposing Factors… Predisposing Factors for Heat Stroke Increased Heat ProductionDecreased Heat Loss Environmental heat stress ExertionCardiac disease FeverPeripheral vascular disease Hypothalamic dysfunctionDehydration Drugs (sympathomimetics)Anticholinergic drugs HyperthyroidismObesity Skin disease Ethanol β Blockers

21. Causes of Hyperthermia… Causes of Hyperthermia Syndromes HEAT STROKE Exertional: Exercise in higher-than-normal heat and/or humidity Drugs including: antihistamines; antiparkinsonian drugs; diuretics DRUG-INDUCED HYPERTHERMIA Amphetamines, cocaine, lithium, anticholinergics NEUROLEPTIC MALIGNANT SYNDROME Phenothiazines; including haloperidol SEROTONIN SYNDROME antidepressants MALIGNANT HYPERTHERMIA Inhalational anesthetics ENDOCRINOPATHY Thyrotoxicosis, pheochromocytoma CENTRAL NERVOUS SYSTEM DAMAGE Cerebral hemorrhage

22. Signs and Symptoms Heat cramps –Cramps in big muscles – spasms –Normal temperature –Caused by dilutional hyponatremia (hypotonic fluid replacement)

23. Signs and Symptoms, cont’d Heat exhaustion –Weakness, dizziness, headache, syncope –Nausea, vomiting –Temperature 39-41.1 o C –Normal mentation –Profuse sweating

24. Signs and Symptoms, cont’d Heat Stroke –Mortality of 10-20% with current treatment –Coma, seizures, confusion –No sweating –Temperature >41.1 o C –Classic triad: hyperpyrexia, CNS dysfunction,

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

26. Diagnostics ECG Imaging guided by history CBC, electrolytes, renal function, LFTs, Urine analysis

27. Poor prognostic factors Temperature > 41.1 o C Coma Renal Failure Hypotension

28. Treatment ABC’s!!! Cooling Remove to cool environment! Correct fluid and electrolyte imbalances