Hydrogen sulfide toxicity

General Information

• Colorless, flammable gas
• Encountered in following industries: oil, gas, organic decomposition (sewer and manure), roofing asphalt tanks
• Most common fatal gas exposure
• “Rotten egg” smell which diminishes with high concentrations or prolonged low concentration exposure
• Often used in suicide attempts: acidic detergent (toilet bowl cleaner) is mixed with bath salts or pesticides</ref>Tintinalli et. al. Hydrogen Sulfide. In: Tintinalli et. al. Emergency Medicine A Comprehensive Study Guide. New York, NY: McGraw Hill. 2011. 1320.</ref>

Mechanisms of toxicity

• Highly lipid soluble
• Disrupts oxidative phosphorylation by inhibiting cytochrome oxidase aa3 (toxicity through cellular asphyxia and impairs ATP production) => lactate accumulation and metabolic acidosis
• Causes hyperpolarization of potassium-mediated channels in neurons
• Potentiates neuronal inhibitory mechanisms
• Alters brain neurotransmitter content and release

Symptoms

• Respiratory: dyspnea, cyanosis, hemoptysis, rales, delayed pulmonary edema
• Ophthalmic: conjunctivitis, corneal ulceration, corneal scarring
• Central nervous system: headache, weakness, disequilibrium, intention tremor, muscle rigidity, loss of consciousness, seizures, coma
• Gastrointestinal: green-gray line on gingiva, nausea, vomiting
• Cardiovascular: chest pain, bradycardia
• Neuropsychiatric: amnesia, lack of insight, disorientation, delirium, dementia
• Death

Differential Diagnosis:

• Carbon Monoxide Toxicity
• Cyanide Toxicity
• Hydrocarbons Toxicity
• Smoke Inhalation Injury

Diagnosis

• No single test to verify exposure or levels
• ABG Interpretation: metabolic acidosis and normal oxygen saturation (unless pulmonary edema present)
• Elevated lactate
• Discolored copper coins found on patient may be helpful in diagnosis</ref>Gresham, C. Hydrogen Sulfide Poisoning. Medscape: http://emedicine.medscape.com/article/815139-overview. Updated Jan 27, 2014. Accessed Aug 8, 2014.</ref>

Treatment

• Removal from source
• 100% oxygen
• Can give nitrite component of cyanide antidote kit (do NOT give the thiosulfate portion):
  • Theoretically increasing methemoglobin formation in blood will cause conversion of sulfide to sulfmethemoglonin (less toxic)
  • Amyl nitrite
  • Sodium nitrite (3% NaNO2) IV over 2-4 minutes; adult dose 10 mL
  • Obtain methemoglobin level 30 minutes after dose (desired level < 30%)
• Hyperbaric oxygen therapy (though not proven to have any benefit)

Disposition

• Admission, likely to MICU
• Toxicology consult