Hypothermia and Cold Weather Injuries

1. HypothermiaandCold Weather Injuries Recognizing, Preventing and Treating Shawn F. Kane, M.D. Kevin deWeber, MD, FAAFP

2. Outline • History • Cold Injury v Heat Injury • Definitions • Physiology/Effects on Organ Systems • Non-Freezing and Freezing cold injuries • Treatment • Field Management

3. Historical Perspective • French invasion of Russia in 1812. Baron de Larrey, chief surgeon, noted mental and physical hardships by Soldiers exposed to the cold • Freeze-thaw-refreeze phenomenon. • George Washington 10% of his troops perished in the winter of 1777-78 due to cold.

4. Historical Perspective • WWII 200,000 Allied and German troops suffer cold related injuries or deaths • Korea 10% of all US fatalities were cold related. • 1950 Battle of Chosin Reservoir. 30K UN troops held off and repelled 60K Chinese • UN: 2.5K KIA, 5K WIA, 7.5K Frostbite/cold weather injuries • Chinese: 25K KIA, 12.5K WIA, 30K Frostbite/cold weather injuries

5. Cold Injury v Heat Injury • Heat Injuries: CDC 1999-2003. 3,442 deaths due to heat. Mean 688/yr • Cold Injuries: CDC 1999-2002. 4,407 deaths due to cold. Mean 689/yr • 60%/40% - underlying cause/contributing factor

6. Definitions • Accidental Hypothermia: the unintentional drop in core body temperature to <35°C (95°F) • Intentional Hypothermia: controlled cooling of core body temperature for specific medical indications (CVA, MI, TBI)

8. DefinitionsTypes of Heat Loss • Radiation:dispersal of heat energy from uncovered skin to nearby objects • >50% of our heat loss • Evaporation:loss of heat via the transformation of liquid water into water vapor. • 20-30% of heat loss • Insensible heat loss can lead to dehydration if not accounted for.

9. DefinitionsTypes of Heat Loss • Conduction:transfer of heat from one object to another through physical contact • Conductivity of water is 23X that of air!! • Immersion injury reduces body temp more rapidly than convective loss • Convection:loss of heat to the air moving next to the body • Windy days • Cycling, running

10. Hypothermia Stages/Classifications ACCIDENTAL Hypothermia of TRAUMA MILD: 34°C – 36°C 93°F - 97°F MODERATE: 32°C – 34°C 90°F - 93°F SEVERE: <32°C <90°F • MILD: 32°C – 35°C 90°F - 95°F • MODERATE: 28°C – 32°C 82°F – 90°F • SEVERE: <28°C <82°F • 33-35(91-95), 31-32(88-90) <31(<88) Shivering Reduced shivering NO shivering Jurkovich GJ. Surg Clin N AM 87(2007) 247-267

11. Human Physiology • Range of 34-40.5°C(95-105°F) to retain normal organ function • Thermoregulatory drive is so important that it takes precedence over many other homeostatic functions • Human body can compensate for hyperthermia better than hypothermia

12. Heat Loss Heat Gain

14. Physiology/Effects on Organ Systems • Initial effects mimic those of sympathetic stimulation • Tremor • Vasoconstriction • Increased O2 consumption • Increased Heart Rate • Increased Minute Ventilation • Continued cold exposure results in inability to compensate

15. Physiology/Effects on Organ Systems • Cardiovascular: • Initial tachycardia progresses to bradycardia starting at 34°C • CO initially increased despite a drop in BP • 50% decrease in HR • <30°C atrial fibrillation, bradycardia and ventricular dysrhythmias • <25°C asystole • At temperature <30°C decreased effects of cardiac medications

16. Physiology/Effects on Organ Systems • Cardiovascular: • Conduction system is VERY sensitive to decrease temperatures. • PR interval, QRS and QT interval prolong as temperature decreases or stays below normal • J or Osborn wave –in 80% of hypothermic patients • Bretylium is the only CV drug that works at decreased temperatures

17. Osborn or J wave Colder the temperature the larger the J wave

18. Physiology/Effects on Organ Systems • Respiratory: • Initially increased but becomes depressed at temperature <33°C • Increased mucous production (bronchorrhea) • Left shift in oxyhemoglobin curve impairing oxygen delivery

19. Physiology/Effects on Organ Systems • GI: • Ileus, bowel wall edema, shallow gastric ulcers (Wischnevsky’s Ulcers) • Decrease hepatic function – drug metabolism • Hemorrhagic pancreatitis, elevated amylase • RENAL: • Initial vasoconstriction contributes to diuresis • Later loss of distal tubular water reabsorption due to dec ADH sensitivity and inc electrolyte excretion

20. Physiology/Effects on Organ Systems • HEME: • Cold platelets DO NOT work • 34°C – 40% decrease in coagulation enzyme function • Hemoconcentration • 1°C drop in temp  2% increase in hematocrit • Normal hematocrit in moderate to severe hypothermia: need to be concerned about blood loss. • Decreased WBC function, increased infection risk

21. Physiology/Effects on Organ Systems • NEUROLOGICAL: • Decreased neural transmission • Incoordination and cognition, numbness • DTRs decrease and eventually flaccid paralysis • <32°C = amnesia • 31°C-27°C lose consciousness • “paradoxical undressing”

22. Hypothermia • Standard clinical thermometers and a false sense of security • Only go down to 34°C(94°F) need low-reading rectal thermometers (<32/90°C/F) • Best accuracy thermometer in place for 3 minutes at a depth of 10 cm • Treat the patient clinically not the classification of hypothermia

23. NOT DEAD UNTIL THEY ARE WARM AND DEAD(unless they are really dead)

24. Hypothermia Treatment • RECOGNIZE THE CONDITION! • Removal from nasty conditions • Removal of wet clothing • Handle with care (testy heart) • Insulate and warm up

25. External blankets hot water bottle heater another body Immersion Internal Warm IV fluids Warmed air Rewarming Methods • Exercise is BAD • Depletes glycogen, reduces shivering • Increases heat loss

26. Hypothermia in Sport • High risk sports • Water sports • Running, cycling • Alpine & cold weather sports

27. Mild Hypothermia in Sports91-95 F • Remove from cold • Insulate • Warm, sweet drink • No alcohol • Minimal to mild activity if improving

28. Moderate Hypothermia88-90 F • Passive rewarming • In field, no active rewarming until rectalT >93F • Monitor rectal temp • Transport to ER for observation

29. Severe Hypothermia<88 T • Handle with care! • Gentle passive rewarming only • Transport immediately, ERICU

30. Non-Freezing Cold Injuries(NFCI) • A clinical syndrome defined as: Injury to soft tissues of the extremities that result from prolonged cooling and/or constant exposure to wet/damp conditions. • Peripheral nerves (then muscle) are most susceptible to cold related injuries. • Sequelae to NFCI may arise immediately after the incident or may not demonstrate themselves for up to 18 months post exposure

31. Non-Freezing Cold Injuries Wet Dry Chilblains or Pernio Exposure to temps <32°C(60°F) Bare skin exposed to dry environment Erythematous, tender, swollen, itchy and painful papules After rewarming – inflamed, red and hot to the touch for hours • Trenchfoot • Prolonged exposure to temps between 0-32°C(32-60°F) for hours to 3-4 days • Swollen, edematous, numb foot • Initially red then becomes pale and cyanotic • Increased sensitivity to pain and infections

32. Non-Freezing Cold Injuries Wet Dry

33. Transient Sequelae: Hyperhidrosis Hyperesthesia/Anesthesia of digits Dec ROM and joint swelling Edema Fat pad loss, transient muscle atrophy Pain from injury to peripheral nerves or small vessels as a result of ischemia Late Sequelae: Hyperesthesia of distal digits Increased sensitivity to heat and cold Nail bed deformities Hyperhidrosis, hypohidrosis or anhidrosis Decreased proprioception Pain Loss of fibrocartilage in ear AVN, growth plate injuries Non-Freezing Cold Injuries(NFCI) ACSM 2005

34. Freezing Cold Injuries (FCI) • A clinical syndrome of temporary or permanent tissue damage that results from the formation of extra/intracellular crystals due to prolonged exposure to sub-freezing temperatures • Extent of damage can be superficial (frostnip) to full thickness (bones and muscles) • Grade 1 through 4 • FCI composed of two parts: immediate and reperfusion

35. Freezing Cold Injuries (FCI) Initial Freeze Injury Reperfusion Injury RBC, WBC and platelet aggregation leads to patchy thrombosis in microcirculation Oxygen free radicals, prostaglandins and thromboxane worsen vasoconstriction and thrombosis MAJORITY of damage occurs during REWARMING • Hyperosmolarity disrupts cell function • Rapid freezing leads to intracellular crystals and immediate cell death • Loss of pain sensation ACSM 2005

36. Freezing Cold Injuries (FCI) ACSM 2005

37. Cold Weather Injury Treatment • Low index of suspicion in an athlete who complains of being cold during or after exercise with a change in sensorium. • ABCs • FIRST priority is to prevent further HEAT LOSS! (shelter from wet, cold, windy environments, dry off)

38. Cold Weather Injury Treatment • DO NOT thaw tissue if there is a risk of re-freezing • DO NOT RUB the affected area • Minimize motion, move horizontally to minimize cardiac irritability • Safety of rescuers 16th Annual AMAA Sports Medicine Symposium

39. Rewarming • PASSIVE: involves the use of blankets to cover body and head to trap heat being lost. • ACTIVE: the application of outside heat to raise body temperature • External – heat blanket/forced hot air system • Internal – introduction of warm fluids into the body • Warm IVF, body cavity lavage, extracorporeal

41. NFCI and FCI TREATMENT • RAPID rewarming is the goal. Trunk>Limbs • Immersion of limb in 40-42°C (102-106°F) water bath • 30-45 minutes – area appears flushed with good circulation when circulation is re-established • Tetanus Toxoid • Benzyl penicillin 600mg q6 for 48-72 hours • Narcotic Pain Relief – very painful!!! 16th Annual AMAA Sports Medicine Symposium

42. HFCI and FCI TREATMENT • Dry skin to prevent maceration. • Prevent further injury (prostaglandins) • Serous blisters – unroof; topical aloe vera • NSAIDS • Prevent Thrombosis • tPA – a few studies demonstrate the benefit of tPA in preventing/minimizing amputations or the amount of amputated tissue 16th Annual AMAA Sports Medicine Symposium

43. TREATMENT Amputation should be delayed 2-3 months MRI/MRA Technetium 99m methylene diphosphonate bone scan (triple phase 1 minute, 2 hours and 7 hours) – as early as 48 hours after admission may help identify viable (hibernating) tissue

44. Transient Sequelae: Hyperhidrosis Hyperesthesia/Anesthesia of digits Dec ROM and joint swelling Edema Fat pad loss, transient muscle atrophy Pain from injury to peripheral nerves or small vessels as a result of ischemia Late Sequelae: Hyperesthesia of distal digits Increased sensitivity to heat and cold Nail bed deformities Hyperhidrosis, hypohidrosis or anhidrosis Decreased proprioception Pain Loss of fibrocartilage in ear AVN, growth plate injuries NFCI and FCI Sequelae AMPUTATION IS THE ULTIMATE LONG-TERM SEQUELAE TO A FCI 16th Annual AMAA Sports Medicine Symposium

45. How much do you amputate?

46. FIELD PASSIVE REWARMING EQPT

47. FIELD ACTIVE REWARMING EQPT

48. Prevention of Cold Injuries • Layered clothing • Cotton BAD • Wetsuits in water sports • Adequate nutrition & hydration • Cancel events if too cold • ACSM: dry bulb <-4F at coldest place

49. Review • Moderate hypothermia: 91-95F • Avoid active rewarming if <93F in field • Dry NFCI: chilblains, pernio • Wet NFCI: trenchfoot • Frostbite: drain SEROUS blisters; give Pcn, NSAID, Tetanus toxoid, pain meds • Cancel events if low Temp <-4F

50. Questions