* Kasia Munson, MD Emergency Medicine

PGY 2

*Define Hypothermia *Pathophysiology of temperature

regulation *Physiologic changes in hypothermia *Labs and Drugs in hypothermia *Various rewarming methods *Disposition

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Accidental Hypothermia is defined as an unintentional drop in core body temperature below 35 C. Mild = 32C – 35C Moderate = 28C – 32C Severe = 65 years old

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*Hypothalamus: Shivering thermogenesis and non-shivering heat conservation and dissipation.

*Cold  hypothalamus  TRH  pituitary

gland  TSH  thyroid gland  thyroxine

*Sympathetic vasoconstriction

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*Evaporation –insensible losses and sweat *Radiation – infrared electromagnetic energy

*Conduction –transfer to a cooler adjacent object

*Convection – transfer convective currents of air or water

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* Decreased Heat Production:

* Impaired Thermoregulation:

Hypopituitarism, Hypothyroidism,

Peripheral failure, Neuropathies, Acute Diabetes, Insufficient fuel, Hypoglycemia, spinal cord transection, Diabetes, Central failure, neurologic, Central Malnutrition, Marasmus/Kwashiorkor, nervous system trauma, Cerebrovascular Extreme exertion, Neuromuscular accident, Hypothalamic dysfunction, inefficiency, Age extremes, Impaired Parkinson's disease, Anorexia nervosa, shivering, Inactivity, Lack of adaptation Cerebellar lesion, Neoplasm, Congenital intracranial anomalies, Multiple sclerosis * Ireased Heat Loss Immersion, Nonimmersion, Induced vasodilation, Pharmacologic, Toxicologic, Erythrodermas, Burns, Psoriasis, Ichthyosis, Exfoliative dermatitis,

* Iatrogenic: Emergency deliveries, Cold infusions, Heatstroke treatment

* Misc Sepsis, Pancreatitis, Carcinomatosis, Cardiopulmonary disease, Vascular insufficiency, Uremia, Paget's disease, Giant cell arteritis, Sarcoidosis, shaken baby syndrome, Multisystem trauma, Shapiro's syndrome, Wernicke-Korsakoff, Hodgkin's disease

*Decreased Heat Production *Increased Heat Loss *Ethanol *Impaired Thermoregulation *Iatrogenic *Infections *Trauma *Miscellaneous Causes

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*Patients may recover completely

after presenting in a rigid, apneic state with fixed and dilated pupils.

*Resuscitative efforts should be

continued until core temperature is at least 30°C to 32°C

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*33-35 C = tachycardia, shivering, Increased BMR, dysarthria, Normal BP, ataxia *29-32 C = stupor, dec O2 use, hypovolemia a.fib/arrhythmias, dec pulse and CO, dec RR, pupils dilated, pulse down 50%, j waves *22-28 C = V.fib, no DTR or brainstem reflexes, acid/base changes, CBF 30%/CO 45% *18 C = Asystole

*Cerebral autoregulation is maintained with an increase in vascular resistance until 25° C.

*Progressive depression of CNS, some responsive with intact reflexes at 27 to 25° C.

*EEG flat < 20C *Reflexes hyperactive to 32C then hypoactive to 26C then disappear.

*Central Nervous System

*Tachycardia progressing to bradycardia *Atrial fibrillation < 32° C.

*Pulse < 50% at 28° C. *Asystole and VF spontaneously < 25° C. *EKG - the Osborn (J) wave

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* Increased RR then progressive decrease * Oxygen unloading capacity is