Hypothermia

1. Hypothermia February 2013 CE Condell Medical Center EMS System Site Code: 107200E-1213 Prepared by: Sharon Hopkins, RN, BSN, EMT-P Rev: 2.11.13

2. Objectives Upon successful completion of the program the EMS provider will be able to: • Describe the thermoregulatory mechanism. • Describe the mechanisms of heat transfer. • Identify risk factors that predispose a patient to an environmental emergency. • Discuss the pathophysiology of cold emergencies. • Identify the normal and critically low body temperatures.

3. Objectives cont’d • List and describe the various cold disorders. • Describe signs and symptoms, and management of cold disorders. • Describe differences of treatment of the arrested patient with a normal body temperature versus a cold presentation. • Actively participate in case scenario discussion. • Review use of a saline lock with and without IV tubing. • Successfully complete the post quiz with a score of 80% or better.

4. Background Hypothermia • Body’s job is to maintain homeostasis • A constant and suitable condition in which the body functions • Normal body temperature is 98.60F (370C) • Hypothermia considered a core temperature less than 950F • Unable to generate sufficient heat production to return to a normal core temperature

5. Thermoregulatory Mechanisms • Body attempts to maintain/regulate the body temperature • Core temperature • Temperature of deep body tissues • Varies minimally from 98.60F (370C) • Can be measured via tympanic or rectal thermometers (additional routes used in hospital) • Tympanic and rectal can reflect core temperatures • Peripheral body temperature measured via oral or axillary temperatures

6. Thermoregulatory Mechanisms cont’d • Production and loss of heat maintained via a balance between the nervous system and negative feedback mechanisms (an action is stopped or negated) • Hypothalamus at base of brain regulates temperature • When heat is sensed, heat generating mechanisms shut off (i.e.: stop shivering) • When decrease in body temperature sensed, heat losing mechanisms shut off (i.e.: stop sweating) • Thermoreceptors located peripherally (i.e.: skin and certain mucous membranes) and centrally (deeper tissues of body)

7. Hypothalamus – Thermoregulatory Center • Sits deep in brain • Thermo-stat for body

8. Thermoregulatory Mechanisms cont’d • Basal metabolic rate – BMR • Metabolism that occurs when body completely at rest • Continually adjusting based on the need of the body • Blood vessels constrict or dilate based on need to conserve heat or dissipate heat • Can develop a difference between peripheral and core body temperatures • Core temperature is the crucial measurement with major organs • Rectal temperatures will reflect core temperatures

9. Mechanisms of Heat Transfer Heat flows from warmer to colder substances • Conduction • Direct contact • Convection • Heat loss to air currents passing over body • Radiation • Heat loss via infrared rays • Evaporation • Change of liquid to vapor; sweat evaporation • Respiration • Via convection, radiation, and evaporation via lungs

10. Conduction • Transfer of heat away from the warmer surface to the cooler surface • Air is poor conductor of heat • Still air is good insulator • Water conducts better than dry air • Example: Sitting on a cold bench at the stadium you warm it up by your body temperature conducting to the colder bench

11. Convection • Heat lost to air currents passing over the body • Amount of heat lost depends on temperature difference between your body and environment plus speed which the air or water currents are moving • Air in motion takes away a lot of heat • Body heat is first conducted to the air before convection occurs • Example: Blowing on your food to cool it down

12. Radiation • Direct emission of heat • Heat radiates from the warmer body and clothing to the cooler environment • The greater the difference between the body and environmental temperature, the greater the heat loss • Example: On a hot summer day you can see the heat radiating off the hot pavement

13. Evaporation • Responsible for 20-30% of heat loss • Wet clothing enhances heat loss • Exhaled respiratory vapors add to the heat loss • Notice how you see your breath in cold weather? • Example: Stepping out of a shower on a cold winter morning, you warm up immediately after drying off

14. Review Question??? • When a person is exposed to cold temperatures and strong winds for extended period of time, heat is lost mainly through: • A. Radiation • B. Convection • C. Conduction • D. Evaporation

15. Answer: B - Convection • Convection occurs when heat is transferred to circulating air (cool air moves across body surface). If person is wearing light clothing and standing in the cold, windy weather, lose heat mostly by convection.

16. Respiration • As you breathe, you inhale ambient air • In cold climates, this can cool the core • When you exhale you lose moisture and with it goes heat • Heat is lost with ventilations via the processes of convection, radiation, and evaporation via lungs • Expired air usually 98.60F (370C) and 100% humidified

17. Heat Conserving Mechanisms • Vasoconstriction • Via sympathetic nervous system • Skin pale, cool • Piloerection – goose bumps • Evolutionary remnant • Increased heat production • Shivering • Chemical thermogenesis (heat generation by body) • Increased thyroxine release •  rate of cell metabolism

18. Predisposing Risk Factors • Age • Especially young children and older adults • Less developed heat-generating mechanisms • General health/ predisposing medical conditions • Hypothyroidism, diabetes, Parkinson’s, malnutrition • Presence of fatigue • Increases poor decision making skills • Duration of exposure • Coexisting weather conditions • Wind chill • Altitude • Humidity level

19. Risk Factors cont’d • Certain medications that interfere with heat-generating mechanisms • Narcotics • Alcohol • Phenothiazines • Barbiturates • Antiseizure meds • Antihistamines • Antipsychotics • Sedatives • antidepressants, • Pain meds like aspirin, acetaminophen, NSAIDS

20. Body Temperature Levels • Normal 96 – 1000F (37.80C) • Mild hypothermia 90 (320C) – 950F (350C) • Severe hypothermia – below 900F (<320C) • Below 860F cardiac resuscitation possible; more favorable above 860F (300C)

21. Complications Anticipated • Dehydration from cold diuresis • Hypoglycemia • Decreased CNS electrical activity • Coagulopathy disorders – clotting problems • Non-cardiogenic pulmonary edema • Cardiac dysrhythmias • Atrial fibrillation common • VF at 820F (<280C) • Asystole at 680F (<200C)

22. Fluid Balance • Cold induced vasoconstriction increases fluid thru kidneys • Respond with diuresis • Tubules reabsorb less water increasing more diuresis • Fluid shifts intravascular space extravascular space intracellular space • Reverses on rewarming so intravascular volume may increase 30% above normal volume

23. Cold or Heat Emergencies • Difficult to determine mechanism of injury by appearance of wounds– cold or heat exposure? • Obtaining history very important • Field treatment does not differ for wound care

24. Pathophysiology • In response to exposure to cold and wet environments, blood vessels vasoconstrict • Vasoconstriction results in a decreased blood flow to tissues especially in the periphery • Ears, nose, fingers, toes • Cellular waste is not cleared and builds up • Dehydration occurs easily in the cold especially if physically active • Injuries can occur at freezing AND non-freezing temperatures

25. Stages of Hypothermia • Shivering • Body’s attempt to generate heat • Begins around 94-970F (34.4 -360C) • Does not function around 84-880F (29-310C) • Mild hypothermia – 93-970F • Conscious but displaying poor judgment and irrational behavior •  B/P, HR, RR to retain & generate heat • Cools more by inhaling cold air and exhaling moisture and heat with ventilations • Skin may be red, pale, or cyanotic

26. Stages of Hypothermia cont’d • Moderate hypothermia – 86-92.90F • Cognitive abilities declined; does not respond to painful stimuli • Progressive muscular rigidity •  B/P, HR, RR leading to cardiac dysrhythmias • Severe hypothermia – core below 860F • Unconscious; no response to pain • VS barely or non-detectable

27. Review Question??? • What does shivering in the presence of hypothermia indicate? • A. Musculoskeletal system damaged • B. Nerve endings are damaged causing loss of muscle control • C. Body is trying to generate more heat thru muscular activity • D. Thermoregulatory system has failed and body temperature is falling

28. Answer: C – Generating more heat • Shivering in presence of hypothermia indicates that body is trying to generate more heat (thermogenesis) through muscular activity • In early hypothermia, shivering is voluntary attempt to produce heat • As hypothermia progresses, shivering is involuntary

29. Frostnip • Skin freezing but deeper tissues unaffected • Usually affects ears, nose, fingers • Usually not painful until rewarming • Skin pale, cold to touch • May report loss of feeling and sensation to injured areas.

30. Progression of Frostbite Damage 2 weeks • Initial insult • 4 weeks

31. Trench Foot • 1st noted in Napoleon’s army 1812 • Particular problem in trench warfare during winters • WW I, WWII, Vietnam War, Falkland’s War 1982 • Has even occurred at winter festivals • 1998, 2007, 2009, 2012 • Can lead to gangrene and amputation

32. Trench Foot • Feet are cold and wet while wearing constrictive footwear • Temperatures do not need to be freezing • Has occurred in 600F temperature with 13 hour exposure • Keeping feet cold and wet for extended periods is the key causative factor • Excessive sweating is a contributory factor • Prevention – keep feet warm and dry!!!

33. Trench Foot • Exposure followed by blistering

34. Frostbite • Freezing of tissue, usually skin, when blood vessels contract • Blood flow and oxygen is reduced to affected body tissues

35. Frostbite • There are three degrees of cold injury • Classified by depth of injury and clinical presentation • Frostnip • Superficial frostbite • Deep frostbite • Ice crystals form; expand and damage surrounding tissue • Damage dependent on length of exposure and depth of damage • If frozen tissue dies, would lead to amputations

36. Frostbite • Normal sensation is lost; area becomes numb • Color change noted in tissues • Most affected are body parts farthest from the core • Nose, ears, fingers, hands, feet, and toes • Highest risk population • Children, elderly, those with circulation problems • Majority of cases in adults 30-49 year-old

37. Frostbite Is this a problem??? • Don’t break blisters • Serve as protective bandaging • Treat as a burn • Can’t tell if wounds are from cold or heat exposure without knowing the history Frostbite on a climber - parts of digits eventually needed amputation

38. Preparing Site for Treatment • Any constrictive jewelry or other pieces MUST be removed • As extremities/digits swell, any circumferential articles will further constrict blood flow • Any article removed from patient MUST be documented that they were removed • Document what you did with the articles • Given to patient/significant other? • Turned over to ED staff?

39. Pain Management • Rewarming is a VERY PAINFUL!!! process • Once started, rewarming must continue regardless of the pain the patient is experiencing • Superficial frostbite is rewarmed over approximately 20- 40 minutes • Deep frostbite may take an hour to rewarm • Constantly reassess pain levels and document

40. Dressing Application • Use fluffy, loosely wrapped dressings • Separate digits with gauze • Do not want skin on skin – may become stuck together and separating will cause more tissue damage

41. Adult Hypothermia/Cold Emergencies • Adult Routine Medical Care (Region X SOP) • Frostbite • Move patient to a warm environment • Rapidly rewarm frozen areas (of frostbite) with warm water if available (1000 – 1080F) OR • Hot packs wrapped in a towel (not with direct contact to fragile tissue) • Handle skin like a burn • Light, dry sterile dressing; skin surfaces not to rub together • Elevate and immobilize • Manage pain appropriately

42. Rewarming Shock • Hazard of rewarming extremities • Drop in core temperature if extremities rewarmed pushing colder blood into core • Recommended to rewarm thorax only and not hands or feet with hot packs • Occurs due to peripheral reflex vasodilation • Cooled blood returns to core and metabolic acid (wastes) from extremities • May have paradoxical drop in core temperature further worsening hypothermia

43. Pain Management Region X SOP • Fentanyl 0.5 mcg/kg IVP/IN/IO • May repeat in 5 minutes • Same dose as initial dose • Max total dosing of 200 mcg • FYI - A 450 pound patient would get 200 mcg by 2 doses • Synthetic narcotic • Less cardiovascular side effects than experienced with Morphine • Availability of IN route is advantage

44. Basic Principles to Interventions • Move the patient to a warmer environment • Get out of the elements of wind, wetness, and cold – prevent further heat loss • Remove any wet clothing • Do not allow any body part to refreeze after warming • A freeze, thaw, refreeze cycle is more damaging to tissue than prolonged freezing alone • Do not massage tissues • Do not allow patient to walk

45. Systemic Hypothermia SOP • Avoid rough handling and excess activity • Apply heat packs to axilla, groin, neck, thorax • Assess for presence of pulse • If present, continue assessment • If absent, cannot withdraw resuscitative efforts until warmed

46. EKG Changes in Hypothermia • Prolongation of the PR interval; then QRS; then QT interval • J waves (Osborn waves) can occur at any temperature less than 900F (32.30C) • Most frequently seen in Lead II and V6 • As temperature drops, J wave increases • Can be confused with ST elevation indicating acute MI

47. J wave (Osborne waves) – Development in Hypothermia

48. Severe Hypothermia • Signs and symptoms • Absence of shivering • Dysrhythmia • Loss of voluntary muscle control • Decrease blood pressure • Undetected pulse and respirations • Cardiac arrest

49. Systemic Hypothermia SOP cont’d • No pulse • Begin CPR • Evaluate extremities – can they be flexed? • If no, • Follow appropriate cardiac protocol based on rhythm noted • If defibrillation required, limit to one shock • Do not administer medications – they will not circulate effectively

50. Systemic Hypothermia SOP cont’d • No pulse • Begin CPR • Evaluate extremities – can they be flexed? • If yes, • Follow appropriate cardiac protocol based on rhythm noted • If defibrillation required, repeat as core temp rises • To administer medications – extend time between medications • Distribution slowed in the cold state