Sunrise over Gulf of Mexico

1. Sunrise over Gulf of Mexico

2. Heat Illness and Heat Stroke • Heat Illness • Inability to maintain normal body temp due to excess heat production or decreased heat transfer to environment

3. 3 Forms of Heat Illness • Heat Stress • Feeling of discomfort, decreased Performance • Normal body temp • Heat Exhaustion • Mild dehydration • Temp 100.4 – 104 • Intense discomfort, thirst, N/V • Transient confusion (No other neuro symptoms) • Heat Stroke • Body temp >104 • Neuro dysfunction

4. Heat Stroke • Classic (nonexertional) • Environmental exposure to heat • Young children, elderly, disabled • Exertional • Young, healthy individuals • Athletes, military recruits • Heavy exercise in high temps and humidity

6. Heat Stroke • Among high school athletes, heat stroke is 3rd leading cause of mortality • May ignore symptoms until they collapse • Risk factors: prolonged exercise in warm, humid environment

7. Physiologic Cooling Mechanisms • Evaporation (of sweat) • Ineffective relative humidity >75% • Convection, conduction, and radiation • Ineffective >95F

9. Much more than little adults • Children are at increased risk for heat illness • Higher metabolic rate- higher heat production • Increased surface area to mass ratio- increased absorption of heat • Smaller absolute blood volume and lower cardiac output- limits transfer of heat from core to surface • Lower sweat rate per gland and start at higher temps • Inadequate fluid replenishment • Longer to acclimate to hot environments (10-14days)

10. Critical Thermal Maximum (CTM) • Degree of elevated body temp and duration that can be tolerated b/f cell damage occurs • Core body temp 107.6 for 45min

11. DDx • Sepsis/Encephalitis • CNS Conditions (Dysregulation) • Congenital anomalies or traumatic brain injury • Status Epilepticus • Toxidromes • Anticholinergics, Salicylate, Stimulants • Serotonin Syndrome • Neuroleptic Malignant Syndrome • Malignant Hyperthermia • Thyroid Storm • Hemorrhagic Shock and Encephalopathy Syndrome

12. Stabilization • ABCDE • Continuous temp monitoring (rectal probe) • Rapid Cooling • Evaporative cooling of greatest benefit • Spray with water while using high-flow fans • Can decrease temp by 0.27F/min • Ice packs to neck, axillae, groin as adjunct • Cooling blankets not as beneficial • Cold water immersion is effective but not practical • Chilled IV saline (little data)

13. Cooling • Bring temp down to <104F as rapidly as possible • Stop cooling measures at 100.4F • Use benzos to stop shivering

14. Treatment of End Organ Dysfunction • Rhabdomyolysis • hyperkalemia, hypocalcemia, hyperphosphatemia • DIC • Acute Renal Failure • Hyponatremic dehydration/ Hypovolemic shock • Cardiogenic shock • Pulmonary edema • Liver failure • Cerebral Edema

15. Outcome • Mortality • Up to 15% in adolescents • Up to 63% in elderly • Permanent neurologic damage t>107.6 • Heat Intolerance

16. Prevention • Infants: avoid excessive bundling or bedding • If sweating at night- dangerous sign • Lightly colored vehicle with window cracked: • 145F in 40minutes • Keep parked cars locked • Increased awareness to high risk groups

17. Sporting Events • Light colored clothing • Never wear material that restricts sweat loss • 500ml within 2hrs prior to event • 250ml q 20 minutes while exercising