Environmental Pathology

Heat related illness

Heat Related Disease

  • Minor Pathology
    • Milaria Rubra: Acute inflammation of sweat ducts caused by blockage of pores
    • Heat Edema: Self-limited, mild edema of feet, ankles, and hands
    • Sunburn: reddening, inflammation, blistering and peeling of the skin
    • Heat Tetany: Respiratory alkalosis, extremity/circumoral paresthesias, carpopedal spasm
    • Heat Cramps: Painful, involuntary, spasmodic contractions of skeletal muscles
  • Major Pathology

Background

  • Mild heat related illness (heat exhaustion or heat cramps) is defined as core temperature less than 104°F (40°C) without central nervous system symptoms
  • Heat stroke is defined as core temperature 104°F or above and central nervous system symptoms 

Wet Bulb Globe Temperature

  • Wet Bulb Globe Temperature Measurement Chart
  • This is a tool that takes into account ambient temperature, relative humidity, wind, and solar radiation from the sun to get a measurement that can be used to monitor environmental conditions during exercise.
    • This can be used to establish guidelines for activity modifications during particular environments.
    • Guidelines should be region specific
    • Device should be used during school sanctioned athletic programs

Pathophysiology

  • Heat gain exceeds heat loss
  • Can occur passively or with exertion
  • Due to a failure of the body to dissipate excessive body heat from exposure to environmental heat or poor heat-dissipation mechanisms
    • Humid environment makes evaporation as a primary cooling mechanism much less effective
    • Loss of air circulation decreases convective heat exchange between the body and the environment 
    • Children are at increased risk due to greater surface area to body mass ratio compared to results
  • Rise of core body temperature causes cytotoxic and inflammatory response which can result in multiorgan failure

Risk Factors

  • Elderly persons are at risk for classical heat stroke due to rising global temperatures and heat waves in urban and inner-city settings in which these persons cannot care for themselves and/or are chronically ill. 
  • Prepubertal children are at risk for classical heat stroke due to underdeveloped thermoregulatory system and small blood volume relative to size which limits the potentials for heat conductance
  • Exertional heat stroke risk often affects populations such as athletes, laborers, and soldiers
  • Other risk factors include
    • Cognitive impairment
    • Socioeconomic status and limited access to air conditioning 
    • Alcohol or substance use
    • Medications such as amphetamines, anticholinergics, antihistamines, beta blockers, benzodiazepines, diuretics, laxatives, neuroleptics, calcium channel blockers
    • Sickle cell trait

Clinical Features

  • Exertional heat stroke can occur within the first 60 minutes of exertion
  • 3 phases of exertional heatstroke:
    • Hyperthermic-neurologic acute phase 
    • Hematologic-enzymatic phase (peaks 24-48 hours after the event)
    • Late renal-hepatic phase (if symptoms for >96 hrs)
  • See associated symptoms in the table below

Differential Diagnosis

  • Meningitis
  • Encephalitis
  • Epilepsy
  • Substance intoxication
  • Severe dehydration
  • Neuroleptic malignant syndrome
  • Serotonin syndrome
  • Thyroid storm
  • Pheochromocytoma crisis

Evaluation

  • Rectal temperature is the most reliable measurement of core body temperature 

Classification

Heat-related Illness Definition Signs/Symptoms Management
Mild heat related illness (heat exhaustion or heat cramps) Core temperature less than 104°F (40°C) without central nervous system symptoms Diarrhea, dizziness, headache, irritability, loss of coordination, nausea/vomiting, syncope, weakness, cramps Move to a cool location, hydration, rest, prolonged stretching of affected muscle groups with cramping, sodium ingestion
Heat Stroke Core temperature 104°F or above and central nervous system symptoms  As above + Confusion/AMS, dizziness, hallucination, headache, nausea/vomiting, syncope, hot skin without perspiration, hypotension, seizures ABC management, Initiate on-site cooling with cold water immersion if available, intravenous hydration to protect renal circulation and prevent rhabdomyolysis, transport for emergency care

Exertional Heat Stroke Specific Management

  • Cold water immersion achieves a cooling rate of about 0.20°C, to 0.35 °C per minute
  • Administer isotonic saline (1-2 Liters/hr) if available
  • Administer benzodiazepines if seizure occurs
  • Exertional heat stroke cooling rate of faster than 0.10°C is safe and improves prognosis
  • Transport to the emergency department after cooling to a body temperature of < 39.0°C
  • Complications: seizure, hypotension, rhabdomyolysis, liver damage, arrhythmias 

Prevention

  • Avoid exertion in extreme environments
  • Use of cooling systems such as air-conditioning, fans, frequent cool showers
  • Check on elderly persons during extreme weather months
  • Acclimation to changing weather environments
  • Avoid hot times of the day for training
  • Remove equipment or clothing that can interfere with sweat evaporation
  • Appropriate hydration routine
  • Scheduled rest periods during activity

Return to Play

  • Mild illness: 24 hours after event if proper rehydration
  • Heat stroke: 1 week minimum
    • Monitor daily weights 
    • Labs normalize
    • Graduated return to play (test for heat tolerance)
    • Address risk factors

Other complications

Resources

Cold Related Illness

Cold Related Diseases

  • Minor
    • Chilblains: Maladaptive vascular response to non-freezing cold causes an inflammatory skin disorder
    • Cold Induced Urticaria: self limiting urticaria which occurs after cold exposure
    • Frostbite: cold thermal injury which occurs when tissues are exposed to temperatures below their freezing point
    • Trench Foot: non-freezing cold injury resulting in peripheral neuropathy
  • Major
    • Anaphylaxis: anaphylaxis associated with cold and exercise
    • Angioedema: angioedema associated with cold and exercise
    • Hypothermia: defined as core body temperature below 35°C (95°F)

Hypothermia

  • Defined as core temperature below 35°C (95°F)
  • Heat loss exceeds heat gain

Risk Factors

  • Windy and wet environments will speed the cooling process
  • Water immersion or avalanche burial can cool victims at a faster rate
  • Decreased heat production (inactivity, fatigue, energy depletion, lack of sleep
  • Hypopituitarism or hypoadrenalism, hypothyroidism, hypoglycemia)
  • Increased heat loss (immersion, rain, wet clothing from sweat, wind, low body fat, burns, open wounds)
  • Impaired thermoregulation (trauma, neuropathies, acute spinal cord transection, CNS lesions, stroke, toxicity, etc)
  • Meds/toxins: CNS depressants & ethanol

Clinical Features

  • Mild (core temperature 32-35°C or 90-95°F) : shivering and increased blood pressure, amnesia, dysarthria, poor judgment, behavior changes
  • Moderate (core temperature 28-32°C or 82-90°F): ataxia, apathy, stupor, shivering actually ceases, pupils dilate. EKG demonstrates atrial fibrillation and/or J waves
  • Severe (core temperature <28°C or <82°F): unconsciousness, ventricular fibrillation, hypoventilation, loss of reflexes or areflexia, hypotension, dilated pupils. EKG demonstrates ventricular arrhythmia

Classification

Cold-Related Illness Environmental Factors Signs/Symptoms Management Follow Up
Frostbite

– Tissue temperature falls below 0°C (32°F)

– Wet skin 

– Exposed skin such as the nose, ears, cheeks, and exposed wrists

– Hands and feet due to peripheral vasoconstriction at low tissue temperatures.

–  History of Raynaud’s phenomenon

Numbness, tingling, burning, aching, sharp pain after rewarming

Skin color may initially appear red and then will become white. 

Avoid further cold exposure and remove wet clothing

Thaw only if refreezing can be prevented. 

Avoid routine antibiotic administration. 

Pain due to thawing can be treated with NSAIDs.

Often requires debridement

Monitor for compartment syndrome or eschar

Wait sometimes several weeks for amputation until after the injury demarcates unless active infection
Trench foot

– Tissue temperature between 0 and 15°C (32-60°F) for prolonged periods of time

– Creation of damp environment for skin

 Swollen and edematous foot with feeling of numbness. The area first appears red and then becomes pale and cyanotic if severe injury

Prevention by keeping skin dry and frequently changing socks

Do not rub the skin

May be value in tetanus prophylaxis

No role for prophylactic antibiotics 

Gradual rewarming of affected area and hydration 

Amitriptyline or gabapentin QHS for pain management 

Prevention by keeping skin dry and frequently changing socks

Return to outdoor environment only if person can maintain warmth to prevent numbness

May need management of peripheral neuropathy with neuropathic agents

Monitor for complications including infection or gangrene
Chilblain (pernio or kibe)

-Tissue temperature below 16°C (60° F)

– Superficial injury after 1-5 hours in cold wet conditions

 Small, swollen, itchy, and erythematous papules which may be tender.

Prevention by keeping skin dry

Lotion to help soothe itching

NSAIDs or acetaminophen for pain relief

Rash is typically self limiting 

If recurrent, can trial calcium channel blocker

Resources

Altitude Related Illness

Background

Pathophysiology

  • Decreased barometric pressure with ascent causes decreased PO2 which causes hypoxemia and tissue hypoxia
  • Hypoventilation and inadequate gas exchange

Risk factors

  • Rapid ascent and higher altitudes >2500 m
  • Advanced COPD (FE1 <30% predicted value), cystic fibrosis restrictive lung disease, decompensated heart failure, high risk pregnancy, myocardial infarction or stroke within the past 90 days, poorly controlled seizure disorder, pulmonary hypertension, sickle cell disease, unstable angina, untreated cerebrovascular abnormality (AVM, aneurysm)

Clinical Features

Lake Louise self-assessment scoring system for AMS

Symptom 0 1 2 3
Headache None  Mild  moderate severe
GI symptoms  Good appetite  Poor appetite or nausea Moderate nausea or vomiting Severe nausea and vomiting 
Fatigue and/or weakness  none Mild  moderate severe
dizziness/light-headedness none mild Moderate  Severe 
AMS Clinical Functional Score (how are symptoms affecting your activity) Not at all  Present but no change in activity Symptoms forced me to stop ascent or descend Had to be evacuated to lower altitude

Differential Diagnosis and Management

Altitude-Related Illness Predisposing Environment Signs/Symptoms Management 
High Altitude Headache

Above 2500 meters

Occurs within 4-24 hours after ascent 

 Headache which is worse at night and with exertion

Stop ascent and rest at current elevation

NSAIDs or acetaminophen

Descent if symptoms worsen or persist 
Acute Mountain Sickness

Above 2500 meters

Occurs within 1-2 days after ascent

Headache plus at least one of the following symptoms: 

Poor appetite

Nausea

Vomiting

Lethargy

Persistent lightheadedness

Stop ascent and rest

NSAIDs or acetaminophen

Consider acetazolamide or dexamethasone. 

Descent if worsens
High Altitude Cerebral Edema

Unusual below 3500 meters

Occurs within the first few days after ascent usually following symptoms of acute mountain sickness

Encephalopathy, altered mental status

ataxia in a person who has already demonstrated evidence of acute mountain sickness. 

Focal neurological deficits are uncommon

If untreated, this leads to death due to cerebral herniation

Descend if possible

Supplemental oxygen or portable hyperbaric chamber

Dexamethasone 8mg once, then 4mg Q6H until descent achieved or signs resolved.
High Altitude Pulmonary Edema

Unusual below 3000 meters

Occurs within the first 2-4 days after ascent

Dyspnea with activity, decreased exercise performance, dry cough. 

Later signs are dyspnea with simple activities, cyanosis, cough with pink frothy sputum, respiratory distress

Descend if possible

Supplemental oxygen or portable hyperbaric chamber

Sustained-release nifedipine, 30mg q12hrs if no oxygen or cannot descent

Prevention

  • Allow time for acclimatization 
  • Risk factors: rate of ascent, altitude when sleeping, level of exertion at high altitude
  • If moderate-high risk ascent, could consider:
    • Acetazolamide 125mg Q12H 
    • Dexamethasone 2mg Q6H

Resources

Dive Related Illness

Diving Related Diseases

Resources

Editors and Contributors

  • Last updated: 8/31/22
  • Contributors (Summer 2022)
    • Carly Chamberlain, D.O. and John Turner, D.O., Christiana Care Family Medicine and Sports Medicine Departments