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Environmental pathology

Last updated: January 13, 2021

Summary

Environmental pathology is the study of conditions that are caused by exposure to environmental factors such as extreme temperature and altitude changes, electricity, wildlife, and any kind of toxin.

Electrical injuries are often multisystem injuries and require a thorough evaluation. Burns of varying degrees are among the most common findings. Exposure to alternating current can lead to potentially life-threatening arrhythmias. Lightning injuries, a rare subtype of electrical injuries, may manifest with characteristic skin findings, such as Lichtenberg figures.

Animal bites and stings are a common cause of visits to the emergency department. Symptoms vary in severity, depending on the organism. Local findings typically include pain, swelling, and paresthesia. Systemic signs of envenomation may be limited to nonspecific symptoms (e.g., nausea and vomiting) or lead to neurotoxicity, autonomic dysfunction, and shock.

High-altitude illness, which typically occurs at elevations > 8,000 ft (∼ 2,500 m), encompasses acute mountain sickness, high-altitude cerebral edema, and high-altitude pulmonary edema. The main trigger is the low level of oxygen, which can lead to hypoxia, tachypnea, polycythemia, pulmonary edema, and cerebral edema during the first hours to days at high altitude.

Overview

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Electrical injury

Electrical current (industrial or residential) injury [1]

  • Epidemiology
    • Electrical injuries account for approx. 4% of admissions to specialized burn services. [2]
    • Setting
      • Children: most often household injury
      • Adults: most often in occupational settings
    • Workplace-related electrical injuries cause approx. 150 deaths per year in the US. [3]
  • Etiology
    • High-voltage sources (> 1000 V): e.g., lightning strike, industrial devices, power supply lines
    • Low-voltage sources (120–1000 V): e.g., household appliances, extension cords, or wall outlets
  • Pathophysiology: Electrical current enters the body (entry point), passes through tissues and organs, and then exits the body (exit point).
    • The majority of tissue damage is a result of thermal injury, which occurs as the electric current converts to heat when entering the tissue.
    • Nonthermal injury includes direct electric injury to nerve tissue and musculoskeletal injury (secondary to tetanic muscle contraction).
    • The severity of the injury depends on:
      • Current
        • Direct current (DC): e.g., in batteries, cars, computers
        • Alternating current (AC): most household electronic devices (e.g., TV, toaster, washing machine) and wall outlets
        • AC is generally more dangerous than DC, because AC is more likely to trigger ventricular fibrillation.
      • Frequency (in Hz): Low-frequency AC (< 300 Hz) causes muscle contraction, which may prevent the individual from letting go of the source, prolonging exposure.
      • Voltage (V): The higher the voltage of a source, the more severe the injury it may cause.
      • Resistance of tissue
        • Dry skin has a higher resistance than wet skin.
        • The lowest resistance is in water.
  • Clinical features: Electrical injury often affects multiple systems.
  • Management: In general, individuals with (suspected) electrical injury should be treated as trauma patients (see “Management of trauma patients”). A thorough evaluation and frequent reassessments are necessary, as some injuries may not be visible at first.
  • Prevention
    • Following workplace safety rules
    • Education about potential sources of household and workplace exposure
    • Outlet guards
    • Proper incorporation of protective circuit-breaking equipment

Lightning injury [1][4]

  • Definition: a type of electrical injury that is caused by a lightning strike
  • Epidemiology [5]
    • Approx. 250 lightning injuries per year in the US
    • Responsible for 20–30 deaths per year in the US (death rate of ∼ 10%)
  • Pathophysiology: A lightning strike is a type of electrical discharge that has voltages above 10 million volts, which generates a shock wave and extreme heat inside the body in less than a second (low exposure time).
  • Clinical features
  • Diagnostics
    • Diagnosis is based on history (e.g., patient with altered mental status found outside in an open space) and clinical findings.
    • Findings on clothing suggestive of lightning injury
      • Grouped holes in clothes
      • Laceration of leather and shoe soles
      • Traces of melting on the body from metal (belt buckles, wristwatches)
  • Prevention: appropriate behavior during thunderstorms
    • Avoid swimming outdoors.
    • Find a safe, enclosed shelter.
    • Stay away from concrete floors, walls, and electronic equipment.

Animal bites and stings

For the general management of animal bites, see ”Bite wounds” and “Rabies risk assessment.”

Snake bites [6][7]

  • Epidemiology [8]
    • ∼ 5,000 venomous snake bites per year in the US
    • Crotaline snakes (pit vipers, e.g., rattlesnakes, copperheads, cottonmouths) are responsible for the majority of snake bites in the US.
  • Clinical features
    • “Dry bites” (bites without envenomation): minor local symptoms
    • Envenomation leads to varying degrees of local and systemic symptoms that depend on the amount and toxicity of the venom (see table below).
Common snake bites

Rattlesnakes

Coral snakes

 Black mamba snake
Distinguishing features
  • Subtle earth-tone colored skin with rattle tail, triangular head, and vertical pupils
  • Alternating red, yellow, and black color bands
  • Long, slender, cylindrical snake with a coffin-shaped head
Geographic location
  • All US states except Maine, Hawaii, and Alaska
  • Southern US and northern Mexico
  • Sub-Saharan Africa

Venom
  • Neurotoxin
  • Causes competitive inhibition of presynaptic and postsynaptic muscarinic AChR
Clinical features of envenomation Local
  • Bite painless or mildly painful
  • Swelling and paresthesia
  • Multiple bite sites
  • No local swelling and minimal tingling sensation
Systemic
  • Diagnostics: usually based on history (description of possible identifying features of the snake) and clinical features
  • Management
    • Antivenom administration
      • For pit viper bites: crotalidae polyvalent immune fab
      • Adverse effects: hypersensitivity, serum sickness
    • Pressure immobilization and/or tourniquets are not recommended as part of routine management in the US. [9]
    • Patients must be closely watched for signs of cardiovascular instability and respiratory compromise.

Spider bites

  • Diagnosis of spider bites is usually based on history and clinical presentation.
  • General treatment includes cleaning of the wound, cooling, and analgesia.
  • They rarely require specific medical treatment.
Common spider bites
Brown recluse spider Widow spider
Distinguishing features
  • Violin-shaped marking on its cephalothorax
  • Black body with varying red marks
  • North American species: characteristic red hourglass mark on the ventral portion of the body
Geographic location
  • South and North America
  • In the US, it is endemic to the Southeast and Midwest.
  • Found in many regions worldwide
  • In the US: Southwest
Venom
  • Necrotoxin
  • Causes local destruction of tissue integrity, leading to tissue necrosis
Clinical features Local
  • Initially painless bite that develops into an erythematous, painful blister within several hours.
  • Bluish-black skin discoloration usually seen within 24 hours
  • Formation of a dark black eschar by the end of the first week
  • Painful bite that turns into a circular red macule and then a target-like lesion
Systemic
  • Muscle pain and rigidity of the extremities, abdomen, and back
  • Autonomic neurologic symptoms can occur.
Specific treatment

Scorpion sting

  • Most scorpion stings in the US are painful but do not cause severe symptoms.

Bark scorpion sting

  • Geographic location: southwestern US
  • Pathophysiology: venom contains a neurotoxin that inhibits the inactivation of the sodium channels → prolonged depolarization → neuronal membrane hyperexcitability
  • Clinical features
  • Diagnostics: based on history and clinical features
  • Treatment: antivenom administration for severe cases

Jellyfish sting

  • Geographic location
    • Worldwide in coastal waters
    • Box jellyfish: Hawaii, Northern Australia, tropical Atlantic
  • Pathophysiology: Jellyfish have tentacles with specialized capsules (nematocysts) that attach to the skin and release venom. The toxicity of the venom depends on the species.
  • Clinical features
  • Diagnostics: based on history and clinical features
  • Treatment: Routine management depends on the jellyfish species and the geographic location. [10]
    • Apply topical vinegar: recommended only for some jellyfish species (e.g., box jellyfish)
    • Remove attached tentacles and rinse the sting site with seawater.
    • Immerse in hot water for pain relief.
    • Administer antivenom in the case of severe stings (e.g., stings affecting large areas, systemic symptoms).

Hymenoptera sting

  • Examples: bees, wasps, yellow jackets, hornets, fire ants
  • Geographic location: worldwide
  • Pathophysiology: Insects from the Hymenoptera order release venom into tissue when stinging, triggering a local skin reaction and potentially life-threatening systemic reactions.
  • Clinical features
    • Local skin reaction at the site of the sting
      • Initial pain
      • Swelling and redness appear within minutes of the sting event.
      • Usually resolves within hours
      • Large local reactions (LLR): gradually extending area of swelling and redness (typically > 10 cm) that lasts for days [11]
    • Systemic allergic reactions, anaphylaxis are possible
  • Diagnostics: primarily a clinical diagnosis
  • Treatment

High-altitude illness

High-altitude illness refers to a group of syndromes that can occur at high altitudes (typically over 8,000 ft or 2,500 m).

Acute mountain sickness (AMS) [12]

Acclimatization to high altitude
Parameter Early changes Late changes
PAO2 and PaO2
  • ↓
  • ↓
PACO2 and PaCO2
  • ↓
  • ↓
Arterial pH
  • ↑
Hb
  • Normal
Arterial O2 content
  • ↓
  • Returned to normal

High-altitude cerebral edema (HACE)

  • Onset: typically 12–72 hours after arrival at high altitude
  • Risk factor: ascending to altitude > 12,000 ft (∼ 3,700 m)
  • Pathophysiology
    • Not fully understood, but generally considered to be an extreme progression of AMS with the same underlying pathophysiology
    • Most likely, increased cerebral vascular permeability and cerebral blood flow lead to high intravascular pressure and cerebral edema.
  • Clinical features
  • Diagnostics
  • Treatment
    • Immediate descent
    • Oxygen supplement
    • Dexamethasone (used as a critical rescue medication that improves the symptoms)
  • Prevention: acetazolamide (accelerates acclimatization), dexamethasone

High-altitude pulmonary edema (HAPE) [13]

References

  1. Luks AM et al.. Acute high-altitude sickness. European Respiratory Review. 2017; 26 (143): p.160096. doi: 10.1183/16000617.0096-2016 . | Open in Read by QxMD
  2. Stream JO, Grissom CK. Update on High-Altitude Pulmonary Edema: Pathogenesis, Prevention, and Treatment. Wilderness and Environmental Medicine. 2008; 19 (4): p.293. doi: 10.1580/07-weme-rev-173.1 . | Open in Read by QxMD
  3. Lavonas EJ, Ruha A-M, Banner W, et al. Unified treatment algorithm for the management of crotaline snakebite in the United States: results of an evidence-informed consensus workshop. BMC Emerg Med. 2011; 11 (1). doi: 10.1186/1471-227x-11-2 . | Open in Read by QxMD
  4. Kanaan NC, Ray J, Stewart M, et al. Wilderness Medical Society Practice Guidelines for the Treatment of Pitviper Envenomations in the United States and Canada. Wilderness Environ Med. 2015; 26 (4): p.472-487. doi: 10.1016/j.wem.2015.05.007 . | Open in Read by QxMD
  5. Ruha A-M, Kleinschmidt KC, et al. The Epidemiology, Clinical Course, and Management of Snakebites in the North American Snakebite Registry. J Med Toxicol. 2017; 13 (4): p.309-320. doi: 10.1007/s13181-017-0633-5 . | Open in Read by QxMD
  6. American College of Medical Toxicology, American Academy of Clinical Toxicology, et al. Pressure immobilization after North American Crotalinae snake envenomation. Clin Toxicol. 2011; 49 (10): p.881-882. doi: 10.3109/15563650.2011.610802 . | Open in Read by QxMD
  7. Treatment of Jellyfish Envenomation. https://www.aafp.org/afp/2014/0515/od1.html. Updated: May 15, 2014. Accessed: December 13, 2020.
  8. Bilò MB, Martini M, Pravettoni V, et al. Large local reactions to Hymenoptera stings: Outcome of re‐stings in real life. Allergy. 2019; 74 (10): p.1969-1976. doi: 10.1111/all.13863 . | Open in Read by QxMD
  9. Gentges J, Schieche C. Electrical injuries in the emergency department: an evidence-based review.. Emerg Med Pract. 2018; 20 (11): p.1-20.
  10. Burn Incidence and Treatment in the United States: 2016. http://ameriburn.org/who-we-are/media/burn-incidence-fact-sheet/. Updated: January 1, 2020. Accessed: November 23, 2020.
  11. Workplace Injury & Fatality Statistics. https://www.esfi.org/workplace-injury-and-fatality-statistics. Updated: January 1, 2020. Accessed: November 23, 2020.
  12. Davis C, Engeln A, Johnson EL, et al. Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Lightning Injuries: 2014 Update. Wilderness Environ Med. 2014; 25 (4): p.S86-S95. doi: 10.1016/j.wem.2014.08.011 . | Open in Read by QxMD
  13. How Dangerous is Lightning?. https://www.weather.gov/safety/lightning-odds. . Accessed: December 11, 2020.
  14. Ritenour AE et al.. Lightning injury: A review. Burns. 2008; 34 (5): p.585-594. doi: 10.1016/j.burns.2007.11.006 . | Open in Read by QxMD
  15. Sanford A, Gamelli RL. Lightning and thermal injuries. Elsevier ; 2014 : p. 981-986