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  • Conduction: Hot to cold by direct contact 2-3% of body loss
    Air 2% loss
    H2o: 32 times more efficient
    Convection: Heat loss of h20 vapor and air movement
    This decreases as temperature increases
    Temp greater than 98.6 you gain heat
    Loss is proportional to wind velocity
    Loose clothing maximizes convection
    Radiation: 55-65% of body loss
    Transfer by electromagnetic waves
    evaporation: Conversion of liquids to a gas
    Dominant mechanism if humans under stress
    Acclimatization: Daily exposure to environment for 100mins/day near maximal adjustment in 7-14 days
    Sweat earlier, sweat at cooler temperature, Inc volume 3-4l/hr,
    Dec. Na content 65meq/kg to 5 meq/kg.
    Must replace free h2o or die
  • Poor: no AC, poor nutrition
    Infants: surface to weight ratio, cannot control environment or access to fluids
    Athletes: Heat Stroke Third leading cause of death in Athletes behind Head injury and heart failure
    sick: Cystic Fibrosis
    Non Acclimated: cars, tents, tanks, engine rooms, hot tubs, etc.
    Medications:B-blockers, diuretics, anticholinergics( TCA, Benadryl, phenothiazines
    ,

Transcript

  • 1. 12/04/2014 . Heat Stroke Dr.Manish Chandra Prabhakar MGIMS Sewagram
  • 2. Case 1-April 2014 MGIMS • 32 year old bank employee reported feeling unwell to his colleagues and took a nap in the afternoon. Did not wake up. Had traveled extensively on his bike in the morning. • On admission GCS 5/15, HR 150/min, BP 90/60, Temp 106F, Skin dry. No rash, meningeal signs, localising signs.
  • 3. • Diagnosed as heat stroke • Aggressive cooling measures, shifted to ICU. • Progressive severe vasodilatory shock – maximum inotropes within 4 hours • Anuric-dialyzed • DIC and bleeding – product support • Progressive severe shock and lactic acidosis-died on day 4
  • 4. “It does not take long either to boil an egg or to cook neurons.” Hamilton D, Anaesthesia 32:271, 1976
  • 5. • Common medical catastrophe during the summer months • Failure of thermoregulatory mechanism coupled with an exaggerated acute phase response • Heat stroke demands urgent attention because – High mortality – Can cause permanent neurological damage • The reason for this presentation
  • 6. How common is it? • Largely under diagnosed and under reported • No reliable Indian data • In this hospital, we see about 30-40 patients per year, of which 12-15 come to the ICU – referral bias
  • 7. Heat Loss • Conduction • Convection • Radiation • Evaporation Acclimatization
  • 8. Nov 2006 Heat Injury Predisposition  3 Factors Influencing Heat Production 1. Increased Internal Heat Production. • Physical Activity • Febrile illness • Pharmacologic agents 2. Increased External Heat Gain • Exposure to high ambient temperature 3. Decreased Ability to Disperse Heat • Pharmacologic agents • Humidity
  • 9. Heat Injury Predisposition • Elderly • Sick – in our hospital wards • Poor • Infants • Institutionalized • Labourers • Medications • Athletes, Military • Explorers • Non-Acclimated
  • 10. No one is exempt!
  • 11. Spectrum of heat illnesses Heat cramps Heat syncope Heat exhaustion Heat stroke
  • 12. Heat cramps • Cramps of most worked muscles • After exertion • Copious sweating during exertion • Copious hypotonic fluid replacement during exertion • Hyperventilation not present in cool environment • Treat with NS or oral salt water
  • 13. Nov 2006 • Results from cumulative effect of peripheral vasodilatation, decreased vasomotor tone and relative volume depletion. • Usually occurs in non acclimated pt’s in early stage of exposure. • Treatment includes rehydration, removal from heat, and rest Heat Syncope
  • 14. Heat exhaustion • Vague malaise, fatigue, headache • Sensorium normal-poor judgment, vertigo • Core temperature < 104°F • Tachycardia, dehydration • Rule out other disease states • If in doubt, treat as heat stroke • Treat - Rest, cool environment • Hydration-IV and oral
  • 15. Heat stroke-clinical diagnosis • Core temperature > 105F or 40.6C • Severe CNS dysfunction (coma, seizures, delirium) • During periods of sustained high ambient temperatures • Dry hot skin common but sweating may persist
  • 16. Heat Stroke-types • Classic – “Summer Heat Waves” – No sweat in 84-100% of patients – More insidious onset – Elderly, poor, debilitated patients – Rhabdomyolysis and ARF rare
  • 17. Heat Stroke-types • Exertional – 50% sweat – Young, healthy, labourers, athletes, military – Rhabdomyolysis and ARF common – Usually have predisposing factor
  • 18. Cellular level • Denaturation of all proteins • Membrane proteins become non functional • Endothelial damage - cytokine storm - sepsis like syndrome • Gut mucosal barrier disruption – translocation of GNB – contributes to sepsis
  • 19. Heat stroke-organ dysfunction CNS • CNS – drowsiness, coma – delirium, Irritability, bizarre behavior, seizures, – Cerebral edema with raised intracranial pressure. • Cerebellum – Highly sensitive to heat – Ataxia common • Total breakdown of thermoregulation • Any neurological disturbance can occur with heatstroke.
  • 20. Remember • In the setting of a heat illness, coma also may be caused by – electrolyte abnormalities, – hypoglycemia, – hepatic encephalopathy, – uremic encephalopathy, – acute structural abnormalities, such as intracerebral hemorrhage due to trauma or coagulation disorders.
  • 21. Heat stroke-organ dysfunction CVS • Shock states Hyperdynamic: Tachycardia Wide pulse presure Hypodynamic: Low intravascular volume
  • 22. CVS • Cardiogenic pulmonary edema – Myocardial hypofunction – Cooling related • Endothelial dysfunction – profound capillary leak
  • 23. Hematological • Thrombocytopenia (aggregation) • DIC – aPTT, PT prolonged, low fibrinogen (protein denaturation)
  • 24. Pulmonary • Type I respiratory failure – ARDS – Pulmonary edema
  • 25. Musculoskeletal • Rhabdomyolysis
  • 26. Renal • Acute renal failure – Volume depletion – Decreased cardiac output – Direct thermal tubular damage – Sepsis syndrome – Rhabdomyolysis
  • 27. • Heatstroke has been reported to affect almost every organ in the body except for the pancreas.
  • 28. Anyone with hyperpyrexia and altered mental state is considered heatstroke until proven otherwise.
  • 29. Heat stroke can also be a nosocomial disease!
  • 30. Differential diagnosis • Acute CNS infection • Cerebral malaria • Severe sepsis • Neuroleptic malignant syndrome • Malignant hyperthermia • Thyroid storm
  • 31. The golden hour of heat stroke
  • 32. Treatment-Cooling methods • Evaporative • Immersion • Strategic ice packs • Ice cold IV fluids • Ice packing • Cooling blankets • Gastric lavage • Peritoneal lavage • Cardiac bypass • Endovascular cooling catheters
  • 33. Ice immersion • Most effective method • Large quantities of ice should be readily available in a large tub • Cumbersome • Difficult to resuscitate • IV access difficult • Vasoconstriction may limit heat exchange
  • 34. Wet the body and clothes-spray Evaporative
  • 35. Precautions • Wet sheets over a patient, without good air flow, will tend to increase temperature and should be avoided • Slow down cooling once core temperature is less than 101°F
  • 36. Cold IV fluids • 15 ml/kg of ice cold IV fluids reduces temp by 1-2°C • Patients need fluid resuscitation as they are usually dehydrated • Cooling more effective in air conditioned environment
  • 37. Dangers while cooling • Pulmonary edema • Overshoot hypothermia
  • 38. Investigations • CBC • PT, aPTT • CPK, LFT, creat. • ABG, Chest X-Ray, ECG • CSF
  • 39. Supportive treatment • Fluid resuscitation followed by inotrope and vasopressor therapy • Ventilation for ARDS • Platelet, FFP and cryoprecipitate support as indicated • Dialysis for ARF • Manage like sepsis
  • 40. Treatment of early complications • Shivering – Chlorpromazine 25-50mgIV only if cooling is not adequate because of shivering • Convulsions – Diazepam, Phenobarbitone, Mannitol to reduce edema • Myoglobinuria – Mannitol and crystalloids
  • 41. Late complications • Nosocomial sepsis • Cerebellar degeneration
  • 42. Take home • Common and deadly • Recognize early – Have a high index of suspicion, even in a hospitalised patient • Early aggressive cooling measures • Rule out differentials • Aggressive organ supportive therapy
  • 43. © Copyright Texas Parks & Wildlife Department