Hydrogen Sulfide Toxicity Workup

Updated: Nov 16, 2019
  • Author: Chip Gresham, MD, FACEM; Chief Editor: Michael A Miller, MD  more...
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Workup

Approach Considerations

Arterial blood gas (ABG) testing usually reveals a marked uncompensated metabolic acidosis. Acidosis is associated with an elevation in serum lactate level. Oxygen tension (pO2) and calculated oxygen saturation are within the reference range unless the patient has concomitant pulmonary edema. As with other hemoglobinopathies, however, measured oxygen saturation often is low and indicates a saturation gap.

Venous blood gas may indicate abnormally high oxygen tension (because of decreased oxygen utilization) resulting in a decrease in the PO2 gradient between arterial and venous blood. Hydrogen sulfide toxicity may be associated with carboxyhemoglobin or methemoglobinemia, depending on the source of the hydrogen sulfide and co-exposure to other toxic gases.

An electrocardiogram may reveal ischemia or infarction patterns.

Chest radiographic findings initially may be normal, but up to 20% of patients present with clinical evidence of acute lung injury. Acute respiratory distress syndrome (ARDS) is viewed as a complication of hydrogen sulfide poisoning. Computed tomography or magnetic resonance imaging scans of the head may also be initially normal, with abnormal findings (eg, basal ganglia lesions) delayed.

Blood levels of sulfide (which is an unstable metabolite) and thiosulfate may be elevated in cases of significant exposure, but these assays are rarely available, especially on short notice.

With significant acute exposure, respiratory paralysis may terminate ongoing exposure and decrease the amount of hydrogen sulfide absorbed and blood levels may be surprisingly low.

Measurement of sulfide and thiosulfate levels is more appropriate for the evaluation of low-level chronic exposures.