venous hyperoxia differentiates between methemoglobinemia and cyanide toxicity
- related: methemoglobinemia has reduced O2 saturation with normal PaO2, cyanide toxicity leads to elevated lactate
- tags:
Hydroxocobalamin is used for the management of cyanide poisoning, which, similarly to methemoglobinemia, results in tissue hypoxia despite ample oxygen supply, and can manifest with many overlapping symptoms (eg, respiratory depression, neurologic decline, hemodynamic instability). However, cyanide poisoning more commonly manifests with venous hyperoxia due to decreased peripheral tissue oxygen extraction. The most common source of exposure is smoke inhalation, although prolonged sodium nitroprusside infusion can also be a cause for patients who are hospitalized; neither has been a concern for this patient.1
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methemoglobinemia has reduced O2 saturation with normal PaO2
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methemoglobinemia, cyanide, carbon monoxide blood gas differences
- increase venous Po2: narrowing of venous-arterial PaO2 gradient (venous hyperoxia differentiates between methemoglobinemia and cyanide toxicity)