heat stroke


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heat stroke

  2. 2. DEFINITION<br />Elevation of the body temperature beyond 104 0 F . <br />Most severe form of the heat-related illnesses <br />Defined as a body temperature higher than 41.1°C (106°F) associated with neurologic dysfunction.<br />
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  4. 4. FORMS<br />Exertional heatstroke (EHS) - young,strenuous physical activity, for a prolonged period of time, in a hot environment. <br />Classic nonexertional heatstroke (NEHS) -sedentary elderly individuals, chronically ill, and very young persons. <br />Both associated with a high morbidity and mortality, if therapy is delayed.<br />
  5. 5. Pathophysiology<br />Maintainence of constant body temperature by balancing heat gain with heat loss. <br />Excessive heat denatures proteins, destabilizes phospholipids and lipoproteins, and liquefies membrane lipids<br />leading to cardiovascular collapse, multi organ failure, and, ultimately, death.<br />
  6. 6. HEAT GENERATION,INTERNAL<br />At rest, basal metabolic processes produce a 100 kcal of heat per hr . <br />Strenuous physical activity can increase heat production more than 10-fold(>1000 kcal/h)<br />Fever, shivering, tremors, convulsions, thyrotoxicosis,sepsis, sympathomimetic drugs increase heat production.<br />
  7. 7. HEAT GENERATION ,EXTERNAL<br />Acquire heat from the environment through mechanisms involved in heat dissipation, including conduction, convection, and radiation. <br />They occur at the level of the skin and require a properly functioning skin surface, sweat glands, and ANS , but may be manipulated by behavioral responses.<br />
  8. 8. HEAT TRANSFER<br />Conduction -transfer of heat between 2 surfaces with differing temp that are in direct contact. <br />Convection - between the body's surface and a gas or fluid with a differing temperature. <br />Evaporation, which refers to the conversion of a liquid to a gaseous phase<br />Radiation - in the form of electromagnetic waves between the body and its surroundings. <br />The efficacy of radiation depends on the angle of the sun, season, and the presence of clouds.<br />During summer, lying down in the sun can result in a heat gain of up to 150 kcal/h.<br />
  9. 9. HEAT LOSS/DESSIPATION<br />Physiologic responses to heat <br />Increase in the blood flow to the skin, major heat-dissipating organ.<br />Dilatation of the peripheral venous system.<br />Stimulation of the eccrine sweat glands to produce more sweat.<br />
  10. 10. RISK GROUP<br />When heat gain exceeds heat loss, the body temperature rises. <br />AT RISK INDIVIDUALS<br />who lack the capacity to modulate the environment (eg, infants). <br />Elderly persons and patients with diminished cardiovascular reserves . <br />Patients with skin diseases and those taking medications that interfere with sweating . <br />
  11. 11. Frequency<br />USA-CDC- 8,015 deaths were attributed to excessive heat exposure from 1979-2003, 334 deaths/yr. <br />3,442 deaths from exposure to extreme heat in US 1999–2003.<br />1998, worst heat waves to strike India in 50 years resulted in > 2600 deaths in 10 wks.<br />Unofficial reports described the number of deaths as almost double .<br />
  12. 12. INDIAN SCENAREO<br />
  13. 13. Indian statastics<br />
  15. 15. Mortality/Morbidity<br />Duration of the temperature elevation.<br /> Delayed theraphy- mortality rate may be as high as 80%; <br />Early diagnosis and immediate cooling -10%. <br />Highest among the elderly population, pts with preexisting disease, those confined to a bed, and those who are socially isolated.<br />
  16. 16. causes<br />Increased heat production<br />Increased metabolism<br />Infections<br />Sepsis<br />Encephalitis<br />Stimulant drugs<br />Thyroid storm<br />Increased muscular activity<br />Exercise((doubles )<br />Convulsions<br />Tetanus<br />Strychnine poisoning<br />Sympathomimetics<br />Thyroid storm<br />Strenuous exercise and status epilepticus can increase heat production 10-fold .<br />Stimulant drugs, including cocaine and amphetamines, can generate excessive amounts of heat by increasing metabolism and motor activity through the stimulatory effects of dopamine.<br />Neuroleptic agents also may elevate body temperature by increasing muscle activity, but, occasionally, these agents may cause neuroleptic malignant syndrome(NMS.<br />Idiosyncratic reaction characterized by hyperthermia, altered mental status, muscle rigidity, and autonomic instability and appears to be due to excessive contraction of muscles.<br />Inhaled volatile anesthetics and succinylcholine, may result in malignant hyperthermia. <br />MH- decreased ability of the sarcoplasmic reticulum to retain calcium, resulting in sustained muscle contraction.<br />
  17. 17. Decreased heat loss<br />Reduced sweating<br />Dermatologic diseases<br />Drugs<br />Burns<br />Reduced CNS responses<br />Advanced age<br />Toddlers and infants<br />Alcohol<br />Barbiturates<br />Other sedatives<br />Reduced cardiovascular reserve<br />Elderly persons<br />Beta-blockers<br />Calcium channel blockers<br />Diuretics<br />Drugs<br />Anticholinergics<br />Neuroleptics<br />Antihistamines<br />Exogenous factors<br />High ambient temperatures<br />High ambient humidity<br />Reduced ability to acclimatize<br />Children and toddlers<br />Elderly persons<br />Reduced behavioral responsiveness: Infants, patients who are bedridden, and patients who are chronically ill are at risk for heatstroke –cannot control their environment and water intake.<br />
  18. 18. Clinical features<br />T> 41°C , anhidrosis associated with an altered sensorium.<br />Classic heatstroke- during environmental heat waves-very young persons ,elderly population, individuals who are chronically ill-failure of the body's heat dissipating mechanisms.<br />EHS –young-healthy individuals who engage in strenuous physical activity-increased heat production.<br />
  19. 19. Exertional heatstroke<br />Hyperthermia, diaphoresis, and an altered sensorium, manifest suddenly during extreme physical exertion in a hot environment.<br />Abdominal and muscular cramping, nausea, vomiting, diarrhea, headache, dizziness, dyspnea, weakness commonly precede the heatstroke . <br />Syncope and LOC observed commonly before the development of EHS.<br />Occurs in young, healthy individuals (eg, athletes, firefighters, military personnel) who, while engaging in strenuous physical activity, overwhelm their thermoregulatory system and become hyperthermic. <br />As their ability to sweat remains intact,EHS pts are able to cool down after cessation of physical activity and may present with T<41°C.<br />Risk factors that increase the likelihood of heat-related illnesses include a preceding viral infection, dehydration, fatigue, obesity, lack of sleep, poor physical fitness, and lack of acclimatization. <br />May occur because of increased motor activity due to drug use, such as cocaine and amphetamines, and as a complication of status epilepticus.<br />
  20. 20. Nonexertional heatstroke<br />Hyperthermia, anhidrosis, and an altered sensorium, which develop suddenly after a period of prolonged elevations in ambient temperatures (ie, heat waves). <br />Core body temperatures greater than 41°C are diagnostic.<br />CNS symptoms, ranging from minor irritability to delusions, irrational behavior, hallucinations, and coma .<br />Anhidrosis due to cessation of sweating is a late occurrence.<br />Other CNS symptoms - seizures, cranial nerve abnormalities, cerebellar dysfunction, and opisthotonos.<br />Initially may exhibit a hyperdynamic circulatory state, but, in severe cases, hypodynamic states may be noted.<br /> Affects people who are unable to control their environment and water intake (eg, infants, elderly persons, individuals who are chronically ill),.<br />people with reduced cardiovascular reserve (eg, elderly persons, patients with chronic cardiovascular illnesses).<br />people with impaired sweating (eg, patients with skin disease, patients ingesting anticholinergic and psychiatric drugs).<br /> Infants - immature thermoregulatory system,.<br />Elderly persons -impaired perception of changes in body and ambient temperatures and a decreased capacity to sweat.<br />
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  22. 22. Heat Stroke Col SR Mehta VSM*, Lt Col DS Jaswal+ MJAFI 2003; 59 : 140-143<br />
  23. 23. Physical features<br />Vital signs<br />Temp->41°C( presence of sweating, evaporating mechanisms, and the initiation of cooling methods<41°C ).<br />Pulse: Tachycardia to rates exceeding 130 .<br />BP: normotensive, with a wide pulse pressure; <br />( hypotension due to vasodilation of the cutaneous vessels, pooling of the blood in the venous system,dehydration, myocardial damage and may signal cardiovascular collapse.)<br />
  24. 24. Central nervous system<br /> Universal in persons with heatstroke. <br />Range from irritability to coma.<br />Pts may present with delirium, confusion, delusions, convulsions, hallucinations, ataxia, tremors, dysarthria, and other cerebellar findings, as well as cranial nerve abnormalities and tonic and dystonic contractions of the muscles.<br />Pts also may exhibit decerebrate posturing, decorticate posturing, or they may be limp.<br />Coma (electrolyte abnormalities, hypoglycemia, hepatic encephalopathy, uremic encephalopathy, and acute structural abnormalities, such as intracerebral hemorrhage due to trauma or coagulation disorders).<br />Cerebral edema and herniation also may occur during the course of heatstroke.<br />
  25. 25. Eyes<br />Examination of the eyes may reveal nystagmus and oculogyric episodes due to cerebellar injury.<br />The pupils may be fixed, dilated, pinpoint, or normal.<br />
  26. 26. Cardiovascular<br />Heat stress places a tremendous burden on the heart. <br />Pts with preexisting myocardial dysfunction do not tolerate heat stress for prolonged periods.<br />Pts commonly exhibit a hyperdynamic state, with tachycardia, low systemic vascular resistance, and a high cardiac index.<br />A hypodynamic state, with a high systemic vascular resistance and a low cardiac index, may occur in patients with preexisting cardiovascular disease and low intravascular volume. <br />A hypodynamic state also may signal cardiovascular collapse.<br />High-output cardiac failure and low-output cardiac failure may occur.<br />
  27. 27. Pulmonary<br />Pts with heatstroke commonly exhibit tachypnea and hyperventilation caused by direct CNS stimulation, acidosis, or hypoxia.<br />Hypoxia and cyanosis - atelectasis, pulmonary infarction, aspiration pneumonia, and pulmonary edema.<br />
  28. 28. Hepatic<br />Jaundice and elevated liver enzymes.<br />Rarely, fulminant hepatic failure occurs, accompanied by encephalopathy, hypoglycemia, and disseminated intravascular coagulation (DIC) and bleeding.<br />
  29. 29. RENAL<br />Musculoskeletal<br />Muscle tenderness and cramping ,rhabdomyolysis.<br />The patient's muscles may be rigid or limp.<br />Renal<br />ARF - hypovolemia, low cardiac output, and myoglobinuria (due to rhabdomyolysis).<br />Pts may exhibit oliguria and a change in the color of urine.<br />
  30. 30. Differential Diagnoses<br />Delirium<br />Meningitis<br />Delirium Tremens<br />Neuroleptic Malignant Syndrome<br />Diabetic Ketoacidosis<br />Tetanus<br />Encephalopathy, Hepatic&Uremic<br />Toxicity, Phencyclidine<br />Hyperthyroidism<br />Toxicity, Salicylate<br />
  31. 31. Work up<br />Complete blood cell count<br />Arterial blood gas analysis: res. alkalosis - direct CNS stimulation ; metabolic acidosis - lactic acidosis<br />Glucose: Hypoglycemia <br />electrolytes;Na,K,PO4,Ca,Mg.<br />Hepatic function tests<br />Muscle function tests<br />Renal function tests<br />CSF- nonspecific pleocytosis, and protein levels may be elevated as high as 150 mg/dL.<br />
  32. 32. Imaging findings in heat stroke<br />Early cerebral edema .<br />loss of gray-white matter differentiation .<br />Patchy high signal intensity of the white matter of cerebral hemispheres and corpus striatum .<br />Central pontinemyelinolysis.<br />Vascular boundary zone infarcts .<br />later stages- diffuse cerebellar atrophy.<br />
  33. 33. MR imaging in heat stroke;Carol T. McLaughlin etal; AJNR Am J Neuroradiol 24:1372–1375, August 2003<br />
  34. 34. MR imaging in heat stroke;Carol T. McLaughlin etal; AJNR Am J Neuroradiol 24:1372–1375, August 2003<br />
  35. 35. MR imaging in heat stroke;Carol T. McLaughlin etal; AJNR Am J Neuroradiol 24:1372–1375, August 2003<br />
  36. 36. Treatment<br />Rapid reduction of the core body temperature .<br />Admission to the hospital for at least 48 hours .<br />lowering the core temp to about 39°C , at least 0.2°C/min .<br />Removal of restrictive clothing and spraying water on the body.<br />Covering the patient with ice water–soaked sheets.<br />Placing ice packs in the axillae and groin .<br />Supplemental oxygen.<br />Infusion of D50W should be considered in all patients <br />
  37. 37. Optimal method of rapidly cooling <br />Ice-water immersion -extremely effective method , increased thermal conductivity of ice water can reduce core body temp <39°C in 20-40 mts.<br />Extremely uncomfortable , subcutaneous vasoconstriction, increases shivering, difficulty monitoring and resuscitating .<br />Evaporative techniques –recent and equally effective without the practical difficulties. <br />Intermittently spraying with warm water while a powerful fan blows across the body.<br />Peritoneal, thoracic, rectal, and gastric lavage with ice water; cold intravenous fluids; cold humidified oxygen; cooling blankets; and wet towels.<br />
  38. 38. TR…….<br />Antipyretics-no role.<br />Stop excessive production of heat -Agitation and shivering with benzodiazepines, Neuroleptics best avoided .<br />Convulsions -Benzodiazepines and, if necessary, barbiturates ;refractory sz-paralysis and ventilation<br />IV fluids-hypovolemia, preexisting medical conditions, and preexisting cardiovascular disease.<br />Metabolic support and symptomatic treatment for ARF,hepatic failure and PE.<br />Rhabdomyolysis -infusion of large amounts of intravenous fluids (fluid requirements may be as high as 10 L), alkalinization of the urine, and infusion of mannitol.<br />Mannitol may improve renal blood flow and glomerular filtration rate, increase urine output, and prevent fluid accumulation in the interstitial compartment (through its osmotic action). Mannitol also is a free radical scavenger and, therefore, may reduce damage caused by free radicals.<br />
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  40. 40. CEREBELLAR ATROPHY<br />The physiology of neurological involvement in heat stroke <br /> Increased intracranial pressure combined with autonomic dysfunction that leads to cerebral hypoperfusion and ischaemia .<br /> Tendency towards intracranial haemorrhage because of abnormal coagulation. <br />The cerebellum is most susceptible to hyperthermia, followed by cerebral cortex, brainstem, and spinal cord.<br />The cerebellar findings may be a combination of these factors coupled with or solely due to the directly destructive effects of hyperthermia on the Purkinje cells.<br /> Post-Heat Stroke CerebellarAtrophy,USudhiretal, JIACM 2009; 10: 60-2<br />Cerebellar syndrome following neuroleptic induced heat stroke ;DAVID LEFKOWITZetal, JNNP;1983;46:183-185<br />