1. Hyperthermia and Hypothermia Back to Basics April 2011 Dr. J. Clow, ER

2. Case 1: 22 y.o. female 22 y.o. female Out with friends celebrating her birthday (February 19 th ) Out with friends celebrating her birthday (February 19 th ) Dropped off at her front door by friends Dropped off at her front door by friends Found by her parents in the morning, passed out just inside the screen door Found by her parents in the morning, passed out just inside the screen door Unable to wake her… call 911 Unable to wake her… call 911

3. Case 2: 85 y.o. male 85 y.o. male Mid-August, during heat wave Mid-August, during heat wave Son goes to apartment and finds patient confused and lethargic Son goes to apartment and finds patient confused and lethargic Patient unable to give history Patient unable to give history

4. Heat Regulation Four mechanisms of heat loss/dissipation: Four mechanisms of heat loss/dissipation: Radiation Radiation Convection Convection Conduction Conduction Evaporation Evaporation

5. Radiation Physical transfer of heat between the body and the environment by electromagnetic waves Physical transfer of heat between the body and the environment by electromagnetic waves 65% of heat transfer under normal circumstances 65% of heat transfer under normal circumstances Modified by insulation (clothing, fat layer), cutaneous blood flow Modified by insulation (clothing, fat layer), cutaneous blood flow

6. Convection Energy transfer between the body and a gas or liquid Energy transfer between the body and a gas or liquid Affected by temperature gradient, motion at the interface, and liquid Affected by temperature gradient, motion at the interface, and liquid Not usually a major source for heat loss or dissipation, but this increases with wind and body motion Not usually a major source for heat loss or dissipation, but this increases with wind and body motion

7. Conduction Direct transfer of heat energy between two surfaces Direct transfer of heat energy between two surfaces Responsible for only a small proportion of heat loss under normal circumstances Responsible for only a small proportion of heat loss under normal circumstances Increases significantly with immersion in cold water Increases significantly with immersion in cold water Major cause of accidental hypothermia Major cause of accidental hypothermia

8. Evaporation Most important source of cooling under extreme heat stress; important for hypothermia when in wet environment Most important source of cooling under extreme heat stress; important for hypothermia when in wet environment 25% of heat loss in temperate/cool conditions… may be increased significantly by sweating, increased respiratory rate 25% of heat loss in temperate/cool conditions… may be increased significantly by sweating, increased respiratory rate Affected by relative humidity and clothing Affected by relative humidity and clothing

9. Hypothermia…

10. Definition Core body temperature less than 35 o C Core body temperature less than 35 o C Mild: 32.2 - 35 o C Mild: 32.2 - 35 o C Moderate: 28 - 32.2 o C Moderate: 28 - 32.2 o C Severe: < 28 o C Severe: < 28 o C

11. Causes… Decreased heat production Decreased heat production Endocrine, insufficient fuel, neuromuscular inactivity Endocrine, insufficient fuel, neuromuscular inactivity Increased heat loss Increased heat loss Accidental/immersion hypothermia, vasodilatation, skin disorders, iatrogenic Accidental/immersion hypothermia, vasodilatation, skin disorders, iatrogenic Impaired thermoregulation Impaired thermoregulation Central (metabolic, drugs, CNS) Central (metabolic, drugs, CNS) Peripheral (spinal cord injury, neuropathy, diabetes, neuromuscular disorders) Peripheral (spinal cord injury, neuropathy, diabetes, neuromuscular disorders)

12. Predisposing Factors Risk Factors for Hypothermia Age extremes Elderly Neonates Outdoor exposure Occupational Sports-related Inadequate clothing Drugs and intoxicants Ethanol Phenothiazines Barbiturates Anesthetics Neuromuscular blockers Others Endocrine-related Hypoglycemia Hypothyroidism Adrenal insufficiency Hypopituitarism Neurologic-related Stroke Hypothalamic disorders Parkinson's disease Spinal cord injury Multisystem Malnutrition Sepsis Shock Hepatic or renal failure Burns and exfoliative dermatologic disorders Immobility or debilitation

13. Signs and Symptoms Clinical Manifestations of Hypothermia SystemMild HypothermiaModerate HypothermiaSevere Hypothermia CNSConfusion, slurred speech, impaired judgment, amnesia Lethargy, hallucinations, loss of pupillary reflex, EEG abnormalities Loss of cerebrovascular regulation, decline in EEG activity, coma, loss of ocular reflex CVSTachycardia, increased cardiac output and systemic vascular resistance Progressive bradycardia (unresponsive to atropine), decreased cardiac output and BP, atrial and ventricular arrhythmias, J (Osborn) wave on ECG Decline in BP and cardiac output, ventricular fibrillation (< 28°C) & asystole (< 20°C) RespiratoryTachypnea, bronchorrheaHypoventilation (decreased rate and tidal volume), decreased oxygen consumption and CO 2 production, loss of cough reflex Pulmonary edema, apnea

14. Signs and Symptoms, cont’d TABLE 110-2. Clinical Manifestations of Hypothermia, cont’d SystemMild HypothermiaModerate hypothermiaSevere Hypothermia RenalCold diuresis Decreased renal perfusion and GFR, oliguria HematologicIncreased hematocrit, decreased platelet & white blood cell counts, coagulopathy, DIC GIIleus, pancreatitis, gastric stress ulcers, hepatic dysfunction MetabolicIncreased metabolic rate, hyperglycemia Decreased metabolic rate, hyper- or hypoglycemia MusculoskeletalIncreased shiveringDecreased shivering (< 32°C, 90°F), muscle rigidity Patient appears dead, "pseudo-rigor mortis"

15. History Often from bystanders/medics Often from bystanders/medics Circumstances surrounding exposure Circumstances surrounding exposure Where, submersion, ambient temperature? Where, submersion, ambient temperature? Length of exposure Length of exposure Mental status changes Mental status changes Any predisposing illness – acute/chronic? Any predisposing illness – acute/chronic? Alcohol/drugs? Alcohol/drugs?

16. Physical Exam Vitals… Vitals… Temperature – want a core temperature Temperature – want a core temperature Where do we take it? Where do we take it? Signs of other injuries? Signs of other injuries? Can you find the cause of hypothermia? Can you find the cause of hypothermia? Any focal findings? Any focal findings? Esp. neurologic, cardiovascular, respiratory Esp. neurologic, cardiovascular, respiratory

17. Diagnositics ECG (always), CXR (most patients) ECG (always), CXR (most patients) Other tests depend on the clinical scenario Other tests depend on the clinical scenario Any signs of trauma? May need imaging… Any signs of trauma? May need imaging… Are you able to take a history? Are you able to take a history? Past medical history? Past medical history? Labs for all: Labs for all: CBC, electrolytes, glucose, renal function, toxicology, coags, ABGs, LFTs, lipase/amylase, cultures CBC, electrolytes, glucose, renal function, toxicology, coags, ABGs, LFTs, lipase/amylase, cultures

18. ECG Changes May see J waves May see J waves late, terminal upright deflection of QRS complex; best seen in leads V3-V6 late, terminal upright deflection of QRS complex; best seen in leads V3-V6 Multiple arrhythmias Multiple arrhythmias Heart block Heart block Atrial fibrillation Atrial fibrillation Ventricular fibrillation Ventricular fibrillation

19. ECG Changes, cont’d

20. Management…

21. Interventions Airway: need for intubation? Airway: need for intubation? Breathing: spontaneous respiration? Breathing: spontaneous respiration? Warmed humidified oxygen – either through an ETT, or via mask Warmed humidified oxygen – either through an ETT, or via mask Circulation: pulse? BP? Circulation: pulse? BP? Large IVs – warmed IV fluids Large IVs – warmed IV fluids Arrhythmias – when do we treat? Arrhythmias – when do we treat? CPR? CPR?

22. Interventions, cont’d Disability Disability GCS GCS Glucoscan, narcan, thiamine Glucoscan, narcan, thiamine C-spine immobilization prn C-spine immobilization prn Exposure Exposure Undress, assess for trauma Undress, assess for trauma Re-cover quickly Re-cover quickly

23. Rewarming Rewarming Techniques Passive rewarming: Removal from cold environment Insulation, Warm blankets (e.g. Bair hugger) Active external rewarming: Warm water immersion Heating blankets set at 40°C Radiant heat Forced air Active core rewarming at 40°C: Inhalation rewarming Heated IV fluids GI tract lavage Bladder lavage Peritoneal lavage Pleural lavage Extracorporeal rewarming

24. Active Rewarming When? When? Cardiovascular instability Cardiovascular instability Temp less than 32 o C Temp less than 32 o C Concominant illnesses Concominant illnesses Extremes of age Extremes of age Failure of passive rewarming Failure of passive rewarming Active external or internal? Active external or internal?

25. Rewarming - Extracorporeal Options for Extracorporeal Rewarming Extracorporeal Rewarming (ECR) TechniqueConsiderations Venovenous (VV)Circuit — CV catheter to CV or peripheral catheter No oxygenator/circulatory support Flow rates 150-400 mL/min ROR 2°-3°C/h Hemodialysis (HD)Circuit — single-or dual-vessel cannulation Stabilizes electrolyte or toxicologic abnormalities Exchange cycle volumes 200-500 mL/min ROR 2°-3°C/h Continuous arteriovenous rewarming (CAVR) Circuit — percutaneous 8.5 Fr femoral catheters Requires BP 60 mmHg systolic No perfusionist/pump/anticoagulation Flow rates 225-375 mL/min ROR 3°-4°C/h Cardiopulmonary bypass (CPB)Circuit — full circulatory support with pump and oxygenator Perfusate-temperature gradient (5°-10°C) Flow rates 2-7 L/min (ave. 3-4) ROR up to 9.5°C/h Note: BP, blood pressure; CV, central venous; ROR, rate of rewarming.

26. Hyperthermia…

27. Definition Core body temperature > 38 o C Core body temperature > 38 o C Caused by a failure of thermoregulation Caused by a failure of thermoregulation Contrast with fever – cause is cytokine activ’n Contrast with fever – cause is cytokine activ’n Spectrum of heat-related illnesses Spectrum of heat-related illnesses Heat cramps Heat cramps Heat exhaustion Heat exhaustion Heat stroke Heat stroke

28. Spectrum Heat cramps Heat cramps Cramps in big muscles – spasms Cramps in big muscles – spasms Normal temperature, mentation Normal temperature, mentation Caused by dilutional hyponatremia (hypotonic fluid replacement) Caused by dilutional hyponatremia (hypotonic fluid replacement)

29. Spectrum, cont’d Heat exhaustion Heat exhaustion Weakness, dizziness, headache, syncope Weakness, dizziness, headache, syncope Nausea, vomiting Nausea, vomiting Temperature 39-41.1 o C Temperature 39-41.1 o C Normal mentation Normal mentation Profuse sweating Profuse sweating

30. Spectrum, cont’d Heat Stroke Heat Stroke Temperature >41.1 o C Temperature >41.1 o C Coma, seizures, confusion Coma, seizures, confusion No sweating No sweating Classic triad: hyperpyrexia, CNS dysfunction, anhidrosis Classic triad: hyperpyrexia, CNS dysfunction, anhidrosis Mortality of 10-20% with treatment Mortality of 10-20% with treatment Classic vs. Exertional Classic vs. Exertional

31. Spectrum, cont’d Heat Stroke: Heat Stroke: Classic (non-exertional): Classic (non-exertional): Persistent environmental exposure Persistent environmental exposure Impaired thermoregulation Impaired thermoregulation Exertional: Exertional: Heavy exercise in setting of high temperature and humidity Heavy exercise in setting of high temperature and humidity

32. Causes of Hyperthermia Increased heat load Increased heat load Heat absorption from environment Heat absorption from environment Heat stroke (exertional, classic) Heat stroke (exertional, classic) Metabolic heat Metabolic heat Diminished heat dissipation Diminished heat dissipation Obesity, anhidrosis, drugs Obesity, anhidrosis, drugs Sepsis Sepsis

33. Predisposing Factors… Predisposing Factors for Heat Stroke Increased Heat ProductionDecreased Heat Loss Environmental heat stress ExertionCardiac disease FeverPeripheral vascular disease Hypothalamic dysfunctionDehydration Drugs (sympathomimetics)Anticholinergic drugs HyperthyroidismObesity Skin disease Ethanol β Blockers

34. Causes of Hyperthermia… Causes of Hyperthermia Syndromes HEAT STROKE Exertional: Exercise in higher-than-normal heat and/or humidity Nonexertional: Anticholinergics, including antihistamines; antiparkinsonian drugs; diuretics; phenothiazines DRUG-INDUCED HYPERTHERMIA Amphetamines, cocaine, phencyclidine (PCP), methylenedioxymethamphetamine (MDMA; "ecstasy"), lysergic acid diethylamide (LSD), salicylates, lithium, anticholinergics, sympathomimetics NEUROLEPTIC MALIGNANT SYNDROME Phenothiazines; butyrophenones, including haloperidol and bromperidol; fluoxetine; loxapine; tricyclic dibenzodiazepines; metoclopramide; domperidone; thiothixene; molindone; withdrawal of dopaminergic agents SEROTONIN SYNDROME Selective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants MALIGNANT HYPERTHERMIA Inhalational anesthetics, succinylcholine ENDOCRINOPATHY Thyrotoxicosis, pheochromocytoma CENTRAL NERVOUS SYSTEM DAMAGE Cerebral hemorrhage, status epilepticus, hypothalamic injury

35. Differential Diagnosis Differential Diagnosis of Heatstroke Drug toxicity: anticholinergic toxicity, stimulant toxicity (phencyclidine, cocaine, amphetamines, ephedrine), salicylate toxicity Drug withdrawal syndrome: ethanol withdrawal Serotonin syndrome Neuroleptic malignant syndrome Generalized infections: bacterial sepsis, malaria, typhoid fever, tetanus Central nervous system infections: meningitis, encephalitis, brain abscess Endocrine derangements: diabetic ketoacidosis, thyroid storm Neurologic: status epilepticus, cerebral hemorrhage

36. History Circumstances (as per hypothermia) Circumstances (as per hypothermia) Exertion? Exertion? Fluids? Fluids? Past medical history – any acute or chronic illnesses that may worsen situation Past medical history – any acute or chronic illnesses that may worsen situation Medications/Drugs Medications/Drugs Trauma? Trauma?

37. Physical Examination Temperature Temperature Where do we take it? And how? Where do we take it? And how? Vitals! Vitals! Look for complications or other causes of the patients symptoms Look for complications or other causes of the patients symptoms Respiratory, cardiac, neurologic examination Respiratory, cardiac, neurologic examination Signs of bleeding Signs of bleeding

38. Diagnostics ECG (all), CXR (most) ECG (all), CXR (most) Imaging guided by history Imaging guided by history CBC, electrolytes, renal function, LFTs, Ca, Mg, PO4, coags, CK CBC, electrolytes, renal function, LFTs, Ca, Mg, PO4, coags, CK Urine – myoglobin Urine – myoglobin Pan-cultures Pan-cultures

39. Poor prognostic factors Temperature > 41.1 o C Temperature > 41.1 o C AST > 1000 AST > 1000 Coma Coma Rhabdomyolysis Rhabdomyolysis Renal Failure Renal Failure Hypotension Hypotension

40. Treatment ABC’s!!! ABC’s!!! Remove to cool environment! Remove to cool environment! Active cooling Active cooling Correct fluid and electrolyte imbalances Correct fluid and electrolyte imbalances Supportive care Supportive care

41. Treatment Comparison of Cooling Techniques TechniqueAdvantagesDisadvantages Evaporative (i.e. wet the patient’s gown, sheets then use fan) Simple, Readily available Noninvasive Easy patient access Relatively effective Shivering Difficult to maintain monitoring electrodes in position Immersion (in cold/ice water) Noninvasive Relatively effective Shivering, Cumbersome Poorly tolerated Logistically difficult to access Difficult to maintain monitoring Ice packing (cover w/ ice) Noninvasive Readily available Shivering Poorly tolerated Strategic ice packs Noninvasive Readily available Combined with other techniques Shivering Poorly tolerated Medium efficiency Cold gastric lavage Generally available Invasive Labor intensive Potential for water intoxication May require airway protection Limited human experience Cold peritoneal lavage Theoretically beneficialInvasive Limited human experience

42. Complications of Heat Stroke Complications of Heatstroke ImmediateDelayed Vital signs Hypotension Hypothermia overshoot Hyperthermic rebound Muscular Shivering Rhabdomyolysis Neurologic Delirium Seizures Coma Cerebral edema CardiacHeart failure PulmonaryPulmonary edemaAcute respiratory distress syndrome RenalOliguriaRenal failure Gastrointestinal Diarrhea Hepatic necrosis Mucosal gastrointestinal hemorrhage Metabolic Hypokalemia Hypernatremia Hyperkalemia Hypocalcemia Hyperuricemia Hematologic Thrombocytopenia Disseminated intravascular coagulation

43. Back to the cases…

44. Case 1: Hypothermia What do you want to know? What do you want to know? Physical Exam? Physical Exam? Labs? Labs? Any imaging? Any imaging? How are you going to treat her? How are you going to treat her?

45. Case 2: Hyperthermia What do you want to know? What do you want to know? Physical Exam? Physical Exam? Labs? Labs? Any imaging? Any imaging? How are you going to treat him? How are you going to treat him?