Methane toxicity

Background

• Simple asphyxiant
  • Inert gases that displace oxygen and decrease FiO2
• Lighter than air
• Explosive
• Natural production by bacteria in GI tract of humans, other animals

Clinical Features

History

• Confined space, particularly at work
  • Mining
  • Large scale animal farming
  • Fossil fuel industry
  • Organic decomposition
• Other people exposed may have similar symptoms

Symptoms

• Wide range, nonspecific
  • Tachycardia
  • Tachypnea
  • Headache
  • Confusion
  • Nausea/vomiting
  • LOC
  • Coma
  • Cardiac arrest

Differential Diagnosis

• Methemoglobinemia
• Altitude related illness
• Primary CNS disease
• ACS

Toxic gas exposure

• Carbon monoxide toxicity
• Chemical weapons
• Cyanide toxicity
• Hydrocarbon toxicity
• Hydrogen sulfide toxicity
• Inhalant abuse
• Methane toxicity
• Smoke inhalation injury
• Ethylene dibromide toxicity

Evaluation

Workup

• Oxygen saturation - decreased, should improve with removal from exposure
• No definitive test for methane
• Consider other diagnostic testing to rule out other causes if unsure exposure or lack of improvement:
  • EKG
  • CXR
  • Head CT
  • ABG
  • Carboxyhemoglobin

Diagnosis

• Clinical/diagnosis of exclusion
  • Often based on history of exposure

Management

• Supplemental oxygen
• Other supportive care as indicated

Disposition

• Discharge
  • If stable vitals, improved mental status, and otherwise asymptomatic
• Admit
  • If needed for further supportive care

See Also

• Carbon monoxide toxicity
• Inhalant abuse
• Toxicology (main)

References

• Kuschner WG, Blanc PD. Kuschner W.G., & Blanc P.D. Kuschner, Ware G., and Paul D. Blanc.Gases & Other Airborne Toxicants. In: LaDou J, Harrison RJ. LaDou J, & Harrison R.J.(Eds.),Eds. Joseph LaDou, and Robert J. Harrison.eds. CURRENT Diagnosis & Treatment: Occupational & Environmental Medicine, 6e. McGraw Hill; 2021.