1. Accidental Hypothermia

2. Pathophysiology

3. Cardiovascular After an initial tachycardia, a progressive bradycardia develops. The pulse usually decreases by 50% at 28° C After an initial tachycardia, a progressive bradycardia develops. The pulse usually decreases by 50% at 28° C The bradydysrhythmia is refractory to atropine The bradydysrhythmia is refractory to atropine Osborn (J) wave is seen at the junction of the QRS complex and ST segment Osborn (J) wave is seen at the junction of the QRS complex and ST segment J waves are potentially diagnostic but not prognostic. J waves are potentially diagnostic but not prognostic. temperature less than 32° C temperature less than 32° C

5. Dysrhythmias All atrial and ventricular dysrhythmias are common in cases of moderate to severe hypothermia All atrial and ventricular dysrhythmias are common in cases of moderate to severe hypothermia Because the conduction system is more sensitive to the cold than the myocardium Because the conduction system is more sensitive to the cold than the myocardium As hypothermia worsens, the PR interval, then the QRS interval, and finally (and most characteristically) the QT interval become prolonged As hypothermia worsens, the PR interval, then the QRS interval, and finally (and most characteristically) the QT interval become prolonged

6. Central Nervous System Hypothermia progressively depresses the CNS Hypothermia progressively depresses the CNS Significant alteration of the brain's electrical activity begins below 33.5° C, and the electroencephalogram goes silent at 19° C to 20° C. Significant alteration of the brain's electrical activity begins below 33.5° C, and the electroencephalogram goes silent at 19° C to 20° C. Cerebral auto regulation is maintained with an increase in vascular resistance until 25° C Cerebral auto regulation is maintained with an increase in vascular resistance until 25° C

7. Renal System cold diuresis cold diuresis Hypothermia depresses renal blood flow, reducing it by 50% at 27° C to 30° C Hypothermia depresses renal blood flow, reducing it by 50% at 27° C to 30° C

8. Respiratory System Hypothermia initially stimulates respiration. Hypothermia initially stimulates respiration. This is followed by a progressive decrease in the respiratory minute volume This is followed by a progressive decrease in the respiratory minute volume Carbon dioxide production decreases 50% with an 8° C fall in temperature Carbon dioxide production decreases 50% with an 8° C fall in temperature

10. Predisposing Factors Endocrinologic failure Hypopituitarism Hypoadrenalis m Hypothyroidism Diabetes Endocrinologic failure Hypopituitarism Hypoadrenalis m Hypothyroidism Diabetes Insufficient fuel Hypoglycemia Malnutrition Marasmus Kwashiorkor Extre me exertion Insufficient fuel Hypoglycemia Malnutrition Marasmus Kwashiorkor Extre me exertion Neuromuscular inefficiency Age extremes Impaired shivering Inactivity Lack of adaptation Neuromuscular inefficiency Age extremes Impaired shivering Inactivity Lack of adaptation Environmental Immers ion Nonimmersion Environmental Immers ion Nonimmersion Induced vasodilation Pharmacol ogic Toxicologic Induced vasodilation Pharmacol ogic Toxicologic Erythrodermas Burns Psoriasis Ichthyosis Exfoliativ e dermatitis Erythrodermas Burns Psoriasis Ichthyosis Exfoliativ e dermatitis

11. FROSTBITEANDOTHER LOCALIZEDCOLD-RELATED INJURIES

12. Chilblains Chilblains,or pernio, is characterized by usually mild but uncomfortable inflammatory lesions of the skin of bared body areas caused by chronic intermittent exposure to cold weather Chilblains,or pernio, is characterized by usually mild but uncomfortable inflammatory lesions of the skin of bared body areas caused by chronic intermittent exposure to cold weather Localized edema, erythema, cyanosis, plaques, nodules, and in rare cases, ulcerations, vesicles, and bullae. Localized edema, erythema, cyanosis, plaques, nodules, and in rare cases, ulcerations, vesicles, and bullae.

15. Trench foot Immersion foot Immersion foot Early symptoms progress from tingling to numbness of the affected tissues. Early symptoms progress from tingling to numbness of the affected tissues. On initial examination, the foot is pale, mottled, anesthetic, pulseless, and immobile, which initially does not change after rewarming. On initial examination, the foot is pale, mottled, anesthetic, pulseless, and immobile, which initially does not change after rewarming. A hyperemic phase begins within hours after rewarming A hyperemic phase begins within hours after rewarming As perfusion returns to the foot over 2 to 3 days, edema and bullae form, and the hyperemia may worsen. As perfusion returns to the foot over 2 to 3 days, edema and bullae form, and the hyperemia may worsen.

18. Treatment Management of chilblains is supportive. Management of chilblains is supportive. The affected skin should be rewarmed, gently bandaged, and elevated. The affected skin should be rewarmed, gently bandaged, and elevated. Oral nifedipine 20 mg three times daily Oral nifedipine 20 mg three times daily Topical corticosteroids (0,025% fluocinolone cream) and even a brief burst of oral corticosteroids, such as prednisone, have been shown to be useful. Topical corticosteroids (0,025% fluocinolone cream) and even a brief burst of oral corticosteroids, such as prednisone, have been shown to be useful.

19. Effective prophylaxis keeping warm, ensuring good boot fit, changing out of wet socks several times a day never sleeping in wet socks and boots, and once early symptoms are identified, maximizing efforts to warm, dry, and elevate the feet. keeping warm, ensuring good boot fit, changing out of wet socks several times a day never sleeping in wet socks and boots, and once early symptoms are identified, maximizing efforts to warm, dry, and elevate the feet. Feet should be kept clean, warm, dry bandaged, elevated, and closely monitored for early signs of infection Feet should be kept clean, warm, dry bandaged, elevated, and closely monitored for early signs of infection

20. Frostbite Frostbite can occur on any skin surface but generally is limited to the nose, ears, face, hands, and feet, penis Frostbite can occur on any skin surface but generally is limited to the nose, ears, face, hands, and feet, penis

21. First-degree injury Characterized by partial skin freezing, erythema, mild edema, lack of blisters, and occasional skin desquamation Characterized by partial skin freezing, erythema, mild edema, lack of blisters, and occasional skin desquamation The patient may complain of transient stinging and burning, followed by throbbing. Prognosis is excellent. The patient may complain of transient stinging and burning, followed by throbbing. Prognosis is excellent.

22. Second-degree injury Characterized by full-thickness skin freezing, formation of substantial edema over 3 to 4 h, erythema, and formation of clear blisters. The blisters form within 6 to 24 h Characterized by full-thickness skin freezing, formation of substantial edema over 3 to 4 h, erythema, and formation of clear blisters. The blisters form within 6 to 24 h Numbness, followed later by aching and throbbing. Prognosis is good. Numbness, followed later by aching and throbbing. Prognosis is good.

24. Third-degree injury Characterized by damage that extends into Characterized by damage that extends into he subdermal plexus. Hemorrhagic blisters form and are associated with skin necrosis and a blue-gray discoloration of the skin. he subdermal plexus. Hemorrhagic blisters form and are associated with skin necrosis and a blue-gray discoloration of the skin. The patient may complain that the involved extremity feels like a "block of wood," followed later by burning, throbbing, and shooting pains. The patient may complain that the involved extremity feels like a "block of wood," followed later by burning, throbbing, and shooting pains. Prognosis is often poor. Prognosis is often poor.

25. Fourth-degree injury Characterized by extension into subcutaneous tissues, muscle, bone, and tendon. Characterized by extension into subcutaneous tissues, muscle, bone, and tendon. There is little edema. The skin is mottled, with nonblanching cyanosis, and eventually forms deep, dry, black, mummified eschar. There is little edema. The skin is mottled, with nonblanching cyanosis, and eventually forms deep, dry, black, mummified eschar. Vesicles often present late Vesicles often present late The patient may complain of a deep pain. The patient may complain of a deep pain. Prognosis is extremely poor Prognosis is extremely poor

27. Treatment

28. FIELD MANAGEMENT The hypothermia and dehydration associated with frostbite should be addressed. The hypothermia and dehydration associated with frostbite should be addressed. Wet and constrictive clothing should be removed. Wet and constrictive clothing should be removed. The involved extremities should be elevated and wrapped carefully in dry sterile gauze, with affected fingers and toes separated. The involved extremities should be elevated and wrapped carefully in dry sterile gauze, with affected fingers and toes separated. Further cold injury should be avoided. Further cold injury should be avoided.

29. Rapid rewarming is the single most effective therapy for frostbite. Rapid rewarming is the single most effective therapy for frostbite. Rewarming in the field is often impractical and sometimes is dangerous. Rewarming in the field is often impractical and sometimes is dangerous. If the victim has frozen feet and the only avenue to evacuation is prolonged ambulation, rewarming can complicate matters significantly. If the victim has frozen feet and the only avenue to evacuation is prolonged ambulation, rewarming can complicate matters significantly. It can be excessively painful It can be excessively painful

30. If rewarming is attempted in the field, only clean water warmed to 40° to 42°C (104° to 107.6°F), as measured by thermometer, should be used. If rewarming is attempted in the field, only clean water warmed to 40° to 42°C (104° to 107.6°F), as measured by thermometer, should be used. The use of hot, untested tap water should be avoided The use of hot, untested tap water should be avoided Attempts to directly warm with dry air, such as campfires and heaters, should be avoided Attempts to directly warm with dry air, such as campfires and heaters, should be avoided Rubbing snow on frostbitten tissue to stimulate circulation is ineffective, destructive, and absolutely contraindicated. Rubbing snow on frostbitten tissue to stimulate circulation is ineffective, destructive, and absolutely contraindicated.

31. EMERGENCY DEPARTMENT MANAGEMENT

32. Rehydration and general warming Rehydration and general warming Rapid rewarming is the core of frostbite therapy and should be initiated as soon as possible. Rapid rewarming is the core of frostbite therapy and should be initiated as soon as possible. The injured extremity should be placed in gently circulating water at a temperature of 40° to 42°C for approximately 10 to 30 min, until the distal extremity is pliable and erythematous. The injured extremity should be placed in gently circulating water at a temperature of 40° to 42°C for approximately 10 to 30 min, until the distal extremity is pliable and erythematous. Frostbitten faces can be thawed using moistened compresses soaked in warm water Frostbitten faces can be thawed using moistened compresses soaked in warm water

33. Anticipate severe pain during rewarming, and treat with parenteral opiates. Anticipate severe pain during rewarming, and treat with parenteral opiates. Clear blisters should be debrided or at least aspirated. Clear blisters should be debrided or at least aspirated. Hemorrhagic blisters should not be debrided Hemorrhagic blisters should not be debrided Therapy with penicillin G 500,000 U IV every 6 h for 48 to 72 h is recommended in prophylaxis Therapy with penicillin G 500,000 U IV every 6 h for 48 to 72 h is recommended in prophylaxis Topical bacitracin Topical bacitracin Silver sulfadiazine has no benefit Silver sulfadiazine has no benefit Tetanus immunization Tetanus immunization Ibuprofen 12mg/kg per d PO Ibuprofen 12mg/kg per d PO

34. Rewarming Techniques Passive rewarming: Passive rewarming: Removal from cold environment Removal from cold environment Insulation Insulation Active external rewarming: Active external rewarming: Warm water immersion Warm water immersion Heating blankets set at 40°C Heating blankets set at 40°C Radiant heat Radiant heat Forced air Forced air

35. Active core rewarming at 40°C: Active core rewarming at 40°C: Inhalation rewarming Inhalation rewarming Heated IV fluids Heated IV fluids GI tract lavage GI tract lavage Bladder lavage Bladder lavage Peritoneal lavage Peritoneal lavage Pleural lavage Pleural lavage Extracorporeal rewarming Extracorporeal rewarming Mediastinal lavage via thoracotomy Mediastinal lavage via thoracotomy

37. HEAT EMERGENCIES The body tends to maintain its core temperature between 36°C and 38°C (96.8°F and 100° F). The body tends to maintain its core temperature between 36°C and 38°C (96.8°F and 100° F). Native thermal regulation mechanisms begin to fail at core temperatures below 35°C and above 40°C Native thermal regulation mechanisms begin to fail at core temperatures below 35°C and above 40°C It is possible to maintain core temperatures of 40°C to 42°C for short periods without adverse effect. It is possible to maintain core temperatures of 40°C to 42°C for short periods without adverse effect. The highest documented core temperature in a survivor of heat stroke is 46.5° The highest documented core temperature in a survivor of heat stroke is 46.5°

38. Physiologic response to heat stress Four primary methods: Four primary methods: Dilatation of blood vessels (particularly in the skin), Dilatation of blood vessels (particularly in the skin), Increased sweat production Increased sweat production Decreased heat production Decreased heat production Behavioral heat control. Behavioral heat control.

40. Blood flow to the skin can increase from a basal level of 0.2 L/min to a maximum of about 8 L/min. Blood flow to the skin can increase from a basal level of 0.2 L/min to a maximum of about 8 L/min. The heart rate increases The heart rate increases Elevated cholinergic stimulation to the skin results in increased sweat production. Elevated cholinergic stimulation to the skin results in increased sweat production.

41. Medications often interfere with heat removal mechanisms. Medications often interfere with heat removal mechanisms. Anticholinergic agents, diuretics, pheno- Anticholinergic agents, diuretics, pheno- thiazine, Beta-blockers, calcium channel blockers, and sympathomimetics thiazine, Beta-blockers, calcium channel blockers, and sympathomimetics

42. CLINICAL FEATURES

43. Heat Edema Heat edema is a self-limited process manifested by the mild swelling of the feet, ankles, and hands that appears within the first few days of exposure to a hot environment. Heat edema is a self-limited process manifested by the mild swelling of the feet, ankles, and hands that appears within the first few days of exposure to a hot environment. No special treatment is necessary. No special treatment is necessary. Elevation of the legs Elevation of the legs Diuretics are not effective and can predispose to volume depletion, electrolyte abnormality Diuretics are not effective and can predispose to volume depletion, electrolyte abnormality

44. Heat Cramps Heat cramps are painful, involuntary, spasmodic contractions of skeletal muscles, usually those of the calves, although they may involve the thighs and shoulders. Heat cramps are painful, involuntary, spasmodic contractions of skeletal muscles, usually those of the calves, although they may involve the thighs and shoulders. Heat cramps may occasionally occur during exercise or, more commonly, during a rest period after several hours of vigorous physical activity. Heat cramps may occasionally occur during exercise or, more commonly, during a rest period after several hours of vigorous physical activity. In fact, the pain associated with heat cramps usually does not respond to opiates alone. In fact, the pain associated with heat cramps usually does not respond to opiates alone.

45. Treatment consists of fluid and salt replacement (PO or IV) and rest in a cool environment. Treatment consists of fluid and salt replacement (PO or IV) and rest in a cool environment. For mild cases, or if an overwhelming number of patients require treatment, a 0.1 to 0.2% saline solution can be given PO. For mild cases, or if an overwhelming number of patients require treatment, a 0.1 to 0.2% saline solution can be given PO. Two 650 mg salt tablets dissolved in quart of water provide a 0.1 % saline solution. Two 650 mg salt tablets dissolved in quart of water provide a 0.1 % saline solution. More severe cases of heat cramps will respond to intravenous rehydration with NS. More severe cases of heat cramps will respond to intravenous rehydration with NS.

47. Heat Tetany Heat tetany is produced by hyperventilation associated with exposure to short periods of intense heat stress. Heat tetany is produced by hyperventilation associated with exposure to short periods of intense heat stress. This syndrome presents as typical hyperventilation resulting in respiratory alkalosis, paresthesia of the extremities, circumoral paresthesia, and carpopedal spasm. This syndrome presents as typical hyperventilation resulting in respiratory alkalosis, paresthesia of the extremities, circumoral paresthesia, and carpopedal spasm. Treatment consists of removal from the heat and decreasing the respiratory rate. Treatment consists of removal from the heat and decreasing the respiratory rate.

48. Heat Syncope Heat syncope is a variant of postural hypotension resulting from the cumulative effect of relative volume depletion, peripheral vasodilatation, and decreased vasomotor tone. Heat syncope is a variant of postural hypotension resulting from the cumulative effect of relative volume depletion, peripheral vasodilatation, and decreased vasomotor tone. Evaluation of patients with heat syncope requires exclusion of metabolic, cardiovascular, and neurological disorders that may produce syncope Evaluation of patients with heat syncope requires exclusion of metabolic, cardiovascular, and neurological disorders that may produce syncope Treatment consists of removal from the heat source, oral or intravenous rehydration, and rest. Treatment consists of removal from the heat source, oral or intravenous rehydration, and rest.

49. Heat Exhaustion Heat exhaustion is an acute heat-related illness that reflects significant volume depletion and mayor may not have an elevated temperature. Heat exhaustion is an acute heat-related illness that reflects significant volume depletion and mayor may not have an elevated temperature. Symptoms : weakness, malaise, lightheadedness, fatigue, dizziness, nausea, vomiting, frontal headache, and myalgias. Symptoms : weakness, malaise, lightheadedness, fatigue, dizziness, nausea, vomiting, frontal headache, and myalgias. Clinical manifestations include orthostatic hypotension, sinus tachycardia, tachypnea, diaphoresis and syncope. Clinical manifestations include orthostatic hypotension, sinus tachycardia, tachypnea, diaphoresis and syncope. The core temperature is variable and can range from normal to 40°C (\ 04°F). The core temperature is variable and can range from normal to 40°C (\ 04°F).

50. Heat exhaustion is treated with volume and electrolyte replacement and rest. Heat exhaustion is treated with volume and electrolyte replacement and rest. Mild cases may be treated with oral electrolyte solutions. Mild cases may be treated with oral electrolyte solutions. Rapid infusion of moderate amounts of intravenous fluids (1 to 2 L of saline solution) may be necessary in some patients who demonstrate significant tissue hypo perfusion. Rapid infusion of moderate amounts of intravenous fluids (1 to 2 L of saline solution) may be necessary in some patients who demonstrate significant tissue hypo perfusion.

51. Heatstroke The classic definition of heatstroke includes the presence of a core temperature higher than 40°C, CNS dysfunction, and anhidrosis. The classic definition of heatstroke includes the presence of a core temperature higher than 40°C, CNS dysfunction, and anhidrosis. Anyone with hyperpyrexia and CNS dysfunction should be considered to have a heatstroke, which is a medical emergency Anyone with hyperpyrexia and CNS dysfunction should be considered to have a heatstroke, which is a medical emergency

52. The CNS is particularly vulnerable in heatstroke, with symptoms such as irritability, confusion, bizarre behavior, combativeness, hallucinations, seizures, or coma. The CNS is particularly vulnerable in heatstroke, with symptoms such as irritability, confusion, bizarre behavior, combativeness, hallucinations, seizures, or coma. The cerebellum is highly sensitive to heat, and ataxia can be an early neurological finding. The cerebellum is highly sensitive to heat, and ataxia can be an early neurological finding.

53. Virtually any neurologic abnormality may be present in heatstroke, including plantar responses, decorticate and decerebrate posturing, hemiplegia, status epilepticus, and coma. Virtually any neurologic abnormality may be present in heatstroke, including plantar responses, decorticate and decerebrate posturing, hemiplegia, status epilepticus, and coma. Seizures are quite common in heatstroke Seizures are quite common in heatstroke

54. TREATMENT OF HEATSTROKE Initial Resuscitation Standard initial resuscitative measures (adequacy of airway, breathing, and circulation; initiation of high-flow oxygen; use of continuous cardiac monitoring and pulse oximetry; and intravenous access) are appropriate. Initial Resuscitation Standard initial resuscitative measures (adequacy of airway, breathing, and circulation; initiation of high-flow oxygen; use of continuous cardiac monitoring and pulse oximetry; and intravenous access) are appropriate.

55. An initial infusion of NS or LR solution at a rate of 250 mL/h is recommended for most patients. An initial infusion of NS or LR solution at a rate of 250 mL/h is recommended for most patients. Glucose level should be promptly assessed with a test strip due to the high incidence of hypoglycemia in exertional heatstroke. Glucose level should be promptly assessed with a test strip due to the high incidence of hypoglycemia in exertional heatstroke. A lumbar puncture and computed tomography of the head may also be indicated as part of the evaluation of altered mental status A lumbar puncture and computed tomography of the head may also be indicated as part of the evaluation of altered mental status

56. Cooling Techniques Rapid reduction of the core temperature to below 40°C (104°F) is the primary goal of treatment and is accomplished by physical cooling techniques. Rapid reduction of the core temperature to below 40°C (104°F) is the primary goal of treatment and is accomplished by physical cooling techniques.