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Heat exhaustion & heat stroke
OVERVIEW: A continuum of increasingly severe heat illnesses caused by dehydration, electrolyte losses, and failure of the body's thermoregulatory mechanisms
• Heat exhaustion is an acute heat injury with hyperthermia due to dehydration
• Heat stroke is extreme hyperthermia with thermoregulatory failure and profound central nervous system dysfunction
System(s) affected: Endocrine/Metabolic, Nervous
Genetics: N/A
Incidence/Prevalence in USA: Dependent on predisposing conditions in combination with environmental factors
Predominant age: More likely in children or elderly
Predominant sex: Male = Female
SIGNS AND SYMPTOMS: • Heat Exhaustion
• Fatigue and lethargy
• Weakness
• Dizziness
• Nausea, vomiting
• Myalgias
• Headache
• Profuse sweating
• Tachycardia
• Hypotension
• Lack of coordination
• Agitation
• Intense thirst
• Hyperventilation
• Paresthesias
• Core temperature elevated but < 103°F (< 39.4°C)
• Heat Stroke
• Exhaustion
• Confusion, disorientation
• Coma
• Hot, flushed, dry skin
• Core temperature > 105°F (> 40.5°C)
CAUSES: Failure of heat-dissipating mechanisms or an overwhelming heat stress leading to a rise in core temperature, dehydration and salt depletion
RISK FACTORS: • Poor acclimatization to heat or poor physical conditioning
• Salt or water depletion
• Obesity
• Acute febrile or gastrointestinal illnesses
• Chronic illnesses - uncontrolled diabetes or hypertension, cardiac disease
• Alcohol and other substance abuse
• High heat and humidity, poor air circulation in environment
• Heavy, restrictive clothing
DIAGNOSIS DIFFERENTIAL DIAGNOSIS: • Other causes of elevated temperature, dehydration or circulatory collapse
• Febrile illnesses, sepsis
• Drug-induced fluid loss
• Cardiac arrhythmia or infarction
• Acute cocaine intoxication
• Malignant hyperthermia (an autosomally inherited disorder of skeletal and cardiac muscle in which patients have abnormal muscle metabolism on exposure to halothane or skeletal muscle reactants)
LABORATORY: • Used primarily to detect end-organ damage
• Electrolytes, urinalysis
• Creatinine, blood urea nitrogen
• Liver enzymes
• Complete blood count
• Increased urine specific gravity
• Results of above studies yield hypernatremia, hyperchloremia, hemoconcentration
Drugs that may alter lab results: Diuretics
Disorders that may alter lab results: N/A
PATHOLOGICAL FINDINGS: Only those associated with major organ system failure
SPECIAL TESTS: N/A
IMAGING: N/A
DIAGNOSTIC PROCEDURES: Rectal temperature monitoring
TREATMENT APPROPRIATE HEALTH CARE: Emergency treatment - best in a hospital setting
GENERAL MEASURES: • Rapid cooling - remove clothing, wet patient down, ice packs
• Fluid and electrolyte replacement with hypotonic oral fluids or IV 0.5-1.0 liter normal saline
• Consider central venous pressure monitoring
SURGICAL MEASURES: N/A
ACTIVITY: Rest with legs elevated
DIET: • Cool or cold clear liquids only (non-carbonated)
• Avoid caffeine
• Unrestricted sodium
PATIENT EDUCATION: • Stress the importance of proper conditioning and acclimatization
• Instruct patients to recognize heat stress signs and symptoms
• Maintain as much skin exposure as possible in hot, humid conditions, while using proper sun block protection
• Avoid dehydration with proper fluids during activity or exercise - 8 oz fluid intake for every 15 minutes of moderate exercise
MEDICATIONS DRUG(S) OF CHOICE: No medications are required in the initial management. Use isotonic saline solution to rehydrate.
Contraindications: N/A
Precautions: N/A
Significant possible interactions: N/A
ALTERNATIVE DRUGS: N/A
FOLLOW UP PATIENT MONITORING: • Rectal temperature monitoring - cooling may be discontinued when the core temperature drops to 102°F (38.9°C) and stabilizes
• Heat stroke patients may require airway management, hemodynamic monitoring and careful fluid and electrolyte administration and monitoring
• Consider central venous pressure monitoring
PREVENTION/AVOIDANCE: Most important factor in preventing heat stress is adequate fluid replacement. Allow acclimatization to hot weather through proper conditioning and activity modification. Dress appropriately with loose-fitting, open weave, light-colored clothing.
POSSIBLE COMPLICATIONS: • May involve failure of any major organ system
• Cardiac arrhythmias or infarction
• Pulmonary edema, adult respiratory distress syndrome
• Coma, seizures
• Acute renal failure
• Rhabdomyolysis
• Disseminated intravascular coagulation
• Hepatocellular necrosis
EXPECTED COURSE AND PROGNOSIS: • Good when mental function is not altered and when serum enzymes are not elevated. Recovery is within 24-48 hours in most cases.
• The mortality rate for heat stroke (10-80%) is directly related to the duration and intensity of hyperthermia as well as to the speed and effectiveness of diagnosis and treatment
MISCELLANEOUS ASSOCIATED CONDITIONS: N/A
AGE-RELATED FACTORS:
Pediatric: Children are more susceptible
Geriatric: Elderly are more susceptible
Others: N/A
PREGNANCY: May be more prone to volume depletion with heat stress
SYNONYMS: • Heat illness
• Heat injury
• Hyperthermia
• Heat collapse
• Heat prostration
ICD-9-CM: 992.5 Heat exhaustion
992.0 Heat stroke
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Chlamydial sexually transmitted diseases
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Syphilis
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