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Environmental Emergencies. Environmental Emergencies. A medical emergency caused by or exacerbated due to exposure to environmental, terrain, or atmospheric pressure. Common terms. Thermoregulation The maintenance of internal body temperature at or near the set point of 36.5 ºC

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Environmental Emergencies


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    1. Environmental Emergencies

    2. Environmental Emergencies • A medical emergency caused by or exacerbated due to exposure to environmental, terrain, or atmospheric pressure

    3. Common terms • Thermoregulation • The maintenance of internal body temperature at or near the set point of 36.5 ºC • Thermogenesis • The regulation of heat production • Thermolysis • Regulation of heat loss

    4. Thermoregulation • Regulatory centre located in posterior hypothalamus • Central thermoreceptor (stimulated by blood temp) near anterior hypothalamus, peripheral thermoreceptors of skin, and some mucous membranes • Control temperature through vasoconstriction / vasodilation, perspiration, and increased circulation to skin

    5. Regulating heat production • Heat is generated through mechanical, chemical, metabolic, and endocrine activities • Mechanical • Shivering • Chemically • Cellular metabolism • Endocrine • Hormone release

    6. Cell metabolism Breathing Sweating Arrector pilli (piloerection) ↑ HR Shunting of blood Dilation/constriction of blood vessels Core shunting Muscle movement Fluid intake ↑ food intake Sleep ADH release ↑ urination Catecholamine release Regulating heat production

    7. Regulating heat loss • Heat is naturally lost through • Radiation • Convection • Conduction • Evaporation

    8. Body Temperature Maintenance • Physiologic responses — controlled by the brain (involuntary, such as shivering and vasoconstriction) • Deliberate actions — (such as exerting yourself or putting on layers of clothing to retain heat when you stop exercising)

    9. Regulating Heat Loss • Heat is lost from the body to the external environment through the skin, lungs, and excretions • The skin is most important in regulating heat loss • Radiation, conduction, convection, and evaporation are the major sources of heat loss

    10. Convection • Happens when air or water with a lower temperature than the body comes into contact with the skin and then moves on • You use convection when you blow on hot food or liquids to cool them • Amount of heat lost depends on the temperature difference between your body and the environment, plus the speed with which the air or water is moving

    11. Convection • If you are not moving, and the air is still, you can tolerate a cold environment quite well • Air in motion takes away a LOT of heat • With air in motion, the amount of heat lost increases as a square of the wind’s speed • A breeze of 8 mph (12.8 km/h) will take away FOUR times as much heat as a breeze of 4 mph (6.4 km/h)

    12. Convection • Above wind speeds of 30 mph (48 km/h), the point becomes moot, because the air does not stay in contact with the body long enough to be warmed to skin temperature • Convective cooling is much more rapid in cold water because the amount of heat needed to warm the water is far greater than the amount of heat needed to heat the same volume of air

    13. Conduction • Transfer of heat away from the body to objects or substances it comes into contact with • This is the one where grabbing a door handle with a moist hand at -40º gives you a chance to stick around... • Stones and ice are good heat conductors, which is why you get cold when you sit on them

    14. Conduction • Air conducts heat poorly — still air is an excellent insulator • Water conductivity is 240 times greater than that of dry air • The ground is also a good heat conductor, which is why you need a foam pad or other insulating barrier under a sleeping bag if you want to stay warm overnight

    15. Conduction • Alcohol is an excellent heat conductor that remains liquid well below the freezing temperature of water • At very cold temperatures, drinking alcohol (ethanol) can result in flash-freezing of tissues inside the mouth • If the back of the throat and the esophagus become frozen this way, the resulting injury is often lethal

    16. Evaporation • Responsible for 20% - 30% of heat loss in temperate conditions • About 2/3 of evaporative heat loss takes place from the skin in thermoneutral conditions • Remaining evaporative heat loss happens in the lungs and airway • In cold weather, airway evaporative heat loss increases as the incoming air is humidified and warmed

    17. Evaporation • In cold weather, 3 - 4 litres of water per day are required to humidify inhaled air • 1500 - 2000 kilocalories (Cal) of heat are lost in this way on a cold day • This fluid loss, if not replaced, results in dehydration, causing a lowered blood volume and increased risk of developing hypothermia

    18. Evaporation • Wet clothing enhances heat loss • Sweat-drenched clothing conducts heat toward surface layers of clothing • Wet outer clothing layers enhance heat loss to the environment through evaporation • A combination of sweat-soaked inner clothing layers and wet outer clothing can be quite lethal

    19. Radiation • Direct emission or absorption of heat • Heat radiates from the body to the clothing, then from the clothing to the environment • The greater the difference between body and environmental temperatures, the greater the rate of heat loss • Clothing that adequately controls the rates of conductive and convective heat loss will compensate for the radiation heat loss

    20. Cold / aquatic emergencies • Localized cold injuries • Hypothermia • Hyperthermia • Drowning • Diving Emergencies

    21. Localized cold Injuries

    22. Classifications/Symptoms • A common classification separates localized cold injury into three categories • Frostnip (the mildest form of cold exposure) • may be treated without loss of tissue • Superficial frostbite • there is at least some minimal tissue loss • Deep frostbite • there is significant tissue loss even with appropriate therapy

    23. Frost nip • AKA chilblains • The mildest and most common form of localized cold injury • Fingertips, ears, nose and toes commonly affected, characterized by numbness, coldness, and pain without swelling • Re-warming is safe even with friction if sure not superficial frostbite

    24. Frostbite • A localized injury that results from environmentally induced freezing of body tissues • Pathophysiology • Ice tissues form • Vascular abnormalities occur • Cellular injury caused • Increased sensitivity to reoccurrence

    25. Frostbite • Predisposing factors • Peripheral neuropathies • PVD • Alcohol / tobacco use • Inadequate protection • Nutritional deficiencies • Medication administration • PmHx frostbite • Injury / illness / fatigue

    26. Superficial Frostbite • Some freezing of dermal tissue • Initial redness followed by blanching • Diminished tactile sensation • Pain

    27. Deep Frostbite • Freezing of dermal and subcutaneous layers • White appearance • Hard (frozen) to palpation • Loss of sensation • Management ?

    28. Frostbite • Edema and blister formation 24 hours after frostbite injury in area covered by tightly fitted boot.

    29. . Deep Frostbite • Gangrenous necrosis 6 weeks after frostbite injury

    30. Hypothermia

    31. Hypothermia • Is defined as a core temperature less than 35°C (95º F). • Most commonly seen in cold climates, but can develop without exposure to extreme environmental conditions • May result from: • A decrease in heat production • An increase in heat loss • A combination of these factors

    32. Hypothermia • If left untreated, hypothermia can kill. • Nobody ever froze to death — instead, they died of hypothermia. • The freezing part came later… • ...and only if the temperature of the surrounding environment was below freezing.

    33. Predisposing Factors • Age • Medical conditions • Prescription and over-the-counter medications • Alcohol or recreational drugs • Previous rate of exertion

    34. Environmental Factors • External environmental factors that may contribute to a medical emergency • Climate • Season • Weather • Atmospheric pressure • Terrain

    35. Progression • Clinical signs and symptoms may be divided into three classes: • Mild • core temperature between 34º and 36º C (93.2º and 96.8º F) • Moderate • core temperature between 30º and 34º C (86º and 93º F) • Severe • core temperature below 30º C (86 º F)

    36. Clinical Features • Mild (34º and 36º C) - ( pissed off stage ) • LOC Withdrawn Slurred Speech • HR Normal (May increase initially) • BP Normal (May increase initially) • Other Shivering

    37. Clinical Features • Moderate (30º and 34º C) - ( stupid ass stage ) • LOC • Confused, sleepy, irrational, Clumsy, Stumbling • HR • Slow and/or weak • May see EKG changes • BP Decreasing • RR Bradypnea • Other • Cyanosis • Dilated Pupils

    38. Clinical Features • Severe (below 30º C) - ( I’m going to die stage ) • LOC Stupor to Unconscious • HR Slow (may be irregular), Absent EKG Changes (high risk) • BP Hypotensive • RR Bradypnea or apnea • Other Cyanosis Dilated Pupils

    39. EKG Changes • Hypothermia causes characteristic EKG changes: • T-Wave inversion • PR, QRS, QT intervals may increase • Muscle Tremor Artifact • Arrhythmias • Sinus Brady, AFib, AFlut, AV Block, PVC’s, VFib, Asystole

    40. Complications • While the risk of complications are low in healthy people, there are a few to be aware of • Most of these result from pre-existing health problems • Pneumonia • Acute pancreatitis • Thromboses

    41. Complications • Pulmonary edema • Acute renal failure due to tubular necrosis • Increased renal potassium excretion leading to alkalosis • Hemolysis (breakdown of red blood cells) • Depressed bone marrow function • Inadequate blood clotting • Low serum phosphorus

    42. Complications • Seizures • Hematuria (blood in the urine) • Myoglobinuria (muscle pigment that looks like blood in the urine) • Simian deformity of the hand • Temporary adrenal insufficiency • Gastric erosion or ulceration

    43. Stages of Hypothermia • Shivering • Apathy or Decreased Muscle Function • Decreased Level of Consciousness • Decreased Vital Signs • Death

    44. Immersion Hypothermia • In relation to hypothermia, cold water has two specific threat characteristics: • Extreme thermal conductivity • The specific heat of water • Worsened with saturation of clothing by water • The body cannot maintain temperature is water less than 92 degrees F

    45. Immersion Hypothermia • Sudden immersed in cold water causes; • Peripheral vasoconstriction causing increased BP • Tachycardia due to anxiety • Lethal dysrhythmias often occur, especially in patients with cardiovascular / cardioelectrical abnormalities

    46. Immersion Hypothermia • Immersion hyperventilation is the first risk… • Immersion in cold water initially causes a breathing pattern of deep, involuntary gasps • Followed by a minute or more of deep, rapid breaths, with tidal volumes about five times normal • Drowning often occurs especially in conjunction with deep immersion or rough water