Substance
Hydrogen sulfide gas

Pathology
Inhibition of oxidative phosphorylation enzymes, potent inhibition of cytochrome oxidase. Exposure results in cellular hypoxia.

Symptoms
Irritated mucous membranes, conjunctivitis, headache, nausea, vomiting, weakness, bradycardia, hypotension, dyspnea, rapid loss of consciousness with larger exposure, pulmonary edema, cyanosis, convulsions, coma, death due to cardiac or respiratory arrest.

Emergency Measures
High-flow oxygen, advanced cardiac life support as indicated, sodium nitrite, blood pressure monitoring, hyperbaric oxygen if available. Methemoglobin level should be recorded 30 min after sodium nitrate infusion.

Comments
If patient is immediately removed from the exposure, recovery may be rapid and complete. More severe exposures have resulted in permanent neurological changes and myocardial ischemia.