HYPOTHERMIA, FROSTBITE AND HEAT ILLNESS Mark Bromley PGY3
Outline • Heat Stroke • Hypothermia • Frostbite
Case • 68 M is brought into the ED for decreased LOC • Found in bed in his apartment • Freezer door was left open PMHx: • CAD, CHF, DMII Meds: • Metoprolol, Altace, Lipitor, ASA, NTG Patch, Gluconorm OE: • 42oC HR: 65 GCS:3 What are this patients HS risk factors? What other diagnoses are you concerned about? How would you like to manage?
Perspective • Disease of the young and the old • Outdoor laborers • Athletes, children, and the elderly • Proportional to climate • US • 20 cases per 100,000 people • 240 deaths annually • #1 cause of death among US soldiers in the 1st gulf war • Heat wave in 2003 (France) caused 14,802 deaths • Life-threatening emergency needing immediate treatment
Terminology Heat wave • Three or more consecutive days during which the air temperature is >32.2°C Heat stress • Perceived discomfort and physiological strain associated with exposure to a hot environment, especially during physical work Hyperthermia • A rise in body temperature above the hypothalamic set point when heat-dissipating mechanisms are impaired (by drugs or disease) or overwhelmed by external (environmental or induced) or internal (metabolic) heat Heat exhaustion • Mild-to-moderate illness due to water or salt depletion that results from exposure to high environmental heat or strenuous physical exercise; signs and symptoms include intense thirst, weakness, discomfort, anxiety, dizziness, fainting, and headache; core temperature may be normal, below normal, or slightly elevated (>37°C but <40°C) Heat stroke • Severe illness characterized by a core temperature >40°C and central nervous system abnormalities such as delirium, convulsions, or coma resulting from exposure to environmental heat (classic heat stroke) or strenuous physical exercise (exertional heat stroke) Multiorgan-dysfunction syndrome • Continuum of changes that occur in more than one organ system after an insult such as trauma, sepsis, or heat stroke
Progression of Disease Mild-to-moderate illness due to water or salt depletion Perceived discomfort and physiological strain Changes in more than one organ system Hot Outside Hot Inside Symptomatic Sick A rise in body temperature above the hypothalamic set point Severe illness characterized by a core temp >40°C and CNS abnormalities
Clinical and Metabolic Manifestations • Hyperthermia • CNS Dysfunction • Tachycardia, Hyperventilation (CO2 < 20) • Respiratory Alkalosis / Metabolic Acidosis • Hypophosphatemia / Hypokalemia • Rhabdomyolysis (↑PO4, ↑K, ↓Ca) • MODS • encephalopathy, rhabdomyolysis, acute renal failure, acute respiratory distress syndrome, myocardial injury, hepatocellular injury, intestinal ischemia or infarction, pancreatic injury, and hemorrhagic complications, DIC, with pronounced thrombocytopenia
Exertional vs Classic Exertional Classic Healthy Predisposing factors/medications Younger Older Exercise Sedentary Sporadic Heat wave occurrence Diaphoresis Anhidrosis Hypoglycemia Normoglycemia DIC Mild coagulopathy Rhabdomyolysis Mild CPK elevation Acute renal failure Oliguria Marked Lactic acidosis Mild acidosis Hypocalcemia Normocalcemia
Case • 68 M is brought into the ED for decreased LOC • Found in bed in his apartment • Freezer door was left open PMHx: • CAD, CHF, DMII Meds: • Metoprolol, Altace, Lipitor, ASA, NTG Patch, Gluconorm OE: • 42oC HR: 65 What are this patients HS risk factors? What other diagnoses are you worried about? How would you like to manage?
Case • 37 F presents altered and hot • Post-op Day 1 PMHx: • Graves OE: • 135 39oC 143/62 (widened pulse pressure) • Moist skin • Loose stools
Case • 45-year-old man who had been outside mowing grass. • EMS later found him unresponsive, and he arrived at the emergency department with a GCS of 3 OE: • His skin was warm and dry • Rectal temperature 42.2°C HR:170/min. Pupils are 7mm and reactive. • Urine tox screen was positive for cocaine and marijuana • He was admitted to the ICU, and rhabdomyolysis developed. • He recovered with supportive care and was discharged 1 week later. What are his risk factors? Why is he dry?
Case • 67 F with dementia • Increased confusion and agitation, requiring haloperidol 1mg at bedtime for ~5 months • Agitated in the ED • Found on the roof of her building • Progressively became minimally responsive, rigid, and incontinent, with a temp of 40.5oC
Case • 58 M with Hyperthermia • Feeling unwell for the past 48h • Shaking Chills – Altered OE: • 40oC 120 75/52 25 • Flushed/warm peripherally
Classic Heat Stroke (non-exertional) • Results from exposure to high temperature • Unable to compensate Thoughts? Approach? • Consider: • Alternate Diagnoses • Hepatic Transaminase elevations may be useful • Treating presumptively (sepsis)
Case • 42 F collapsed just shy of the finish line • It was her first marathon, and a hot day. But according to her friend she had been keeping “pretty well hydrated.” • Brought to the ED via EMS confused • Tonic-clonic in the trauma bay Risk Factors? Concerns? Management?
Exertional Heat Stroke • Results from strenuous exercise • Typically young healthy people (athletes/workers) • Thoughts? • Consider: • Hydration • Hyponatremia
Treatment • Cooling • Active cutaneous vasodilation • ↑ temperature gradient b/w skin and environment (conduction) • ↑ gradient of water-vapor pressure b/w skin and environment (evaporation) • ↑ velocity of air adjacent to the skin (convection) HEAT HEAT How would you like to do it?
Evaporation / Convection • Cool water or wet sheets applied to the skin • Fan • Spritz or Mist • This rarely causes shivering
Conduction • †Internal cooling, which has been investigated in animals, is infrequently used in humans. Gastric or peritoneal lavage with ice water may cause water intoxication. Rectal lavage Cold water immersion has been linked with asystolic arrests Used by the military without incident May be more significant in “classic” heat stroke (14% mortality study of 28 patients with CHS)
Conduction This may cause shivering • How can you stop it? • If the pt is shivering: • Vigorous massage • spray with tepid water (40°C) • expose to hot moving air (45°C) …either at the same time as cooling methods are applied or in an alternating fashion
Case • A buddy recently back from visiting out east, tells us it was way hotter than anything we’ve experienced here. • According to the Canadian Weather Services the average temperature was exactly the same. • “Yeah but it was a wet hot! It was way hotter!” What do you think? Does humidity make a difference?
Case • 68 M with Heat Stroke • You continue to cool • His BP falls to 68/40 • How would you like to manage?
Fever vs Hyperthermia • Fever does not cause primary pathologic or physiologic damage • Fever does not require therapeutic intervention …unless the patient has limited physiologic reserve
Decreasing the Set Point • Antipyretics • Not useful in true Heat Shock • May be useful in mixed presentations (ie. Sepsis/Heatshock)
Prevention • Acclimatize yourself to heat • Schedule outdoor activities during cooler times • ↓ level of physical activity • Drink additional fluids • Consume salty foods • ↑ amount of time spent in air-conditioning • Automobiles should be locked, and children should never be left unattended in an automobile during hot weather
Acclimatization Successive exposures over weeks… • Enhanced CV performance • Activation of Renin-Angiotensin-Aldosterone Axis • Salt conservation by sweat glands • Increased capacity to secrete sweat • Expansion of plasma volume • Increase in GFR • Increase in ability to resist rhabdomyolysis
Case • 48 F presents with decreased LOC • Found outside by police talking strangely to passers-by • Complaining about her bulky coat • Undressing despite the cold • What is your approach? • Differential Diagnosis? • Why is this lady at risk? • How is she losing heat?
Pathophysiology • Evaporation • Vaporization of water through both insensible loss and sweat • Radiation • Emission of infrared electromagnetic energy • Conduction • Direct transfer of heat to an adjacent, cooler object • Convection • Direct transfer of heat to convective air currents
Pathophysiology Cell membrane dysfunction Efflux of intracellular fluid Enzymatic dysfunction Electrolyte imbalances
Case OE: • 48 10 110/62 34oC • CNS Depression (GCS 5) – No focal findings • Reflexes globally reduced • Not shivering • But she feels cold! • What would you like to do?
Assessment • Thermometer • Need a “low” reading thermometer • Oral temps influenced by respiration • Tympanic temps unreliable • Rectal Probe • “Core” temp • Altered if adjacent to cold/frozen stool • Esophageal Probe • Next to the Aorta • Bladder Probe
Case OE: • Repeat temperature via rectal probe = 28oC • What’s going on Doctor? • Is Hypothermia a diagnosis? • How would you classify?
Clasification • Mild: 32-35oC • tachypnea, tachycardia, ataxia, dysarthria, impaired judgement, shivering, “cold diuresis” • Moderate: 28-32oC • decreased heart rate, hypoventilation, CNS depression, hyporeflexia, decreased renal blood flow, loss of shivering, paradoxical undressing, AFIB, junctional bradycardias • Severe: <28oC • pulmonary edema, oliguria, areflexia, coma, hypotension, bradycardia, ventricular arrhythmias, asystole
Differential Diagnosis Why is this patient hypothermic?
Case What investigations would you like to order?
Investigations • C/S (hypoglycemia) • CBC, Lytes, INR/PTT • ABG • EKG • Anything else you’d like?
Coagulopathy • Clotting factors are temperature dependant …they don’t work when they’re cold • Coags are performed in the lab at 37°C ...thus, clinical coagulopathy → “N” INR and PTT