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Accidental Hypothermia Laura Klouda, MD Intro • Definition – Unintentional drop in body temperature of about 2°C from “normal” (normal = 37.2-37.7°) • Contributing factors/stressors – – – – – – – – Extremes of age Nutritional status/dehydration Pre-existing health conditions Intoxicants/medications that potentially decrease thermostability Exposure type Fatigue and lack of sleep Trauma Wet clothing • Treatment depends on duration and severity of hypothermia and contributing factors/stressors Nervous system effects • Shivering (more effective at producing heat than voluntary muscle contraction) • Memory loss • Impaired judgment • Decreased level of consciousness • Slurring of speech Cardiovascular effects • Bradycardia – Due to slowed pace-maker cell depolarization refractory to atropine • Decreased cardiac output • EKG changes – Prolonged PR, QRS, and QTc – J (Osborn) waves • Dysrhythmias • All of these can be worsened during afterdrop – Afterdrop is a drop in core temp after the warming process has begun Respiratory effects • Initially tachypnea • Bradypnea as hypothermia worsens – Thus CO2 retention and respiratory acidosis • Noncardiogenic pulmonary edema • Increased and thickened secretions Renal effects • Decreased blood flow to kidneys decreased glomerular filtration rate results in build up of nitrogenous waste products • An initial large diuresis results in hemoconcentration. Then followed by oligo/anuria. Effects on coagulation • Bleeding – Due to cold-induced hypercoagulability and thrombocytopenia – Appears similar to DIC (disseminated intravascular coagulation) • Hyperviscosity of blood due to hemoconcentration from diuresis and also from stiffening of red blood cells Physical exam findings • HEENT – Mydriasis, decreased extraocular movements, facial edema and/or flushing, epistaxis and/or rhinorrhea • Cardiovascular – Initial tachycardia followed by bradycardia, dysrhythmia, jugular venous distension, hypotension • Respiratory – Initial tachypnea followed by bradypnea/apnea, increased adventitious lung sounds • GI/GU – Constipation, abdominal distension, emesis, polyuria to anuria • Neuro – Decreased LOC, ataxia, amnesia, initial hyperreflexia followed by areflexia, mood/personality changes • Skin/Musculoskeletal – Shivering, increased muscle tone, erythema, pallor, cyanosis, frostbite, edema Pre-hospital management • Basic principles: – – – – Rescue and remove from cold exposure Physical exam Remove wet clothing, stabilize injuries, cover wounds Body temperature IV fluids if possible • Place bag under patient’s buttocks or in a compressor • Warm fluids by taping hand/feet warmers to fluid bag – Limit rewarming to: • Hot water bottles covered in stockings/mittens placed in patient’s axillae/groin/neck – Be cautious not to burn the patient • Heated insulation • Inhalation of heated humidified oxygen – Patient should remain horizontal – Insulate and wrap patient • Sleeping bags, clothing, tents, etc. – Transport to hospital – Only consider surface re-warming if medical care is unavailable • Body-body contact, warm objects, radiant heat Pre-hospital life support • Avoid jostling or quick movements of comatose patients – They are extremely likely to go into ventricular fibrillation if jostled • Primary objective = prevent further heat loss • Never assume death when patient is still cold. • “No one is dead until warm and dead” IV glucose, naloxone, and flumazenil Pre-hospital life support • Rescue breathing may be difficult due to stiffened muscles • Common problem is overventilation causing hypocapnic ventricular instability • Indications for intubation are the same as for a normothermic patient – Avoid overinflation of the cuff in freezing temperatures. The cuff will expand upon reaching warmer temps can kink tube and/or damage trachea • Palpate/auscultate pulses for a full minute before deciding if patient requires chest compressions – Often bradycardic with low cardiac output – Unnecessary chest compressions can cause ventricular fibrillation • If cardiac monitor and defibrillator available: – Defibrillate if ventricular fibrillation or asystole – Pads generally don’t stick well to cold skin • May need tincture of benzoin Emergency Department Care • IV/O2/Monitor • Warmed IV normal saline • Monitor vitals and confirm hypothermia – Doppler may be needed to obtain a pulse – Rectal thermometer inserted 15cm or esophageal temps are generally reliable • Thermal stabilization – Heat via conduction/convection/radiation/respiration • Maintain tissue oxygenation – CPR/rescue breathing • Determine 1° vs 2° hypothermia • Obtain labs: CBC, blood gas, CMP, INR, PTT, fibrinogen • Rewarm – Passive external, active external, and/or active core rewarming • Treat injuries, infections, underlying medical problems Passive external rewarming • Ideal for mild hypothermia • Insulation with blankets, aluminized body covers, etc. Active Rewarming • For moderate-severe hypothermia (T<32°C), • passive warming failure, peripheral vasodilation, secondary hypothermia, endocrine insufficiency External warming – Hot water bottles, forced circulated hot air e.g. Bair Hugger, heating blankets, etcapply to THORAX, not extremities • Core warming – Heated humidified oxygen, heated IV fluids, gastric/colonic/mediastinal/thoracic/peritoneal lavage with warm saline, extracorporeal blood rewarming Medications in hypothermia • Medications are temperature dependent • Often ineffective during hypothermia then • • become toxic during warming Poor GI absorbtiondo not give oral meds Erratic intramuscular absorbtionavoid IM meds Hypothermia summary • Symptoms often vague, wide variety of presenting symptoms • Pre-hospital treatment – – – – – – Rescue Remove wet clothing, stabilize injuries Limit rewarming Gentle handling, keep horizontal Insulate Transport to hospital – – – – – IV/O2/Monitor Warmed IV normal saline CPR/rescue breathing Passive external, active external, and/or active core rewarming Treat injuries, infections, underlying medical problems • Emergency Dept Treatment • Reference: • Auerbach, P.S. (1995), Wilderness Medicine, 3rd edition. Mosby.
