methemoglobinemia, cyanide, carbon monoxide blood gas differences

• related: ICU intensive care unit
• tags: #literature #icu

---

• methemoglobinemia: methemoglobin absorbs different wavelength of light
  • pulse ox is low: 80s despite 100% FiO2
  • PaO2 normal or high: often 200-300 mmHg
  • elevated methemoglobin (MetHb) in ABG
• in CO poisoning, CO binds hemoglobin with higher affinity than O2
  • pulse ox is normal: does not distinguish between oxyhemoglobin and carboxyhemoglobin
  • ABG shows elevated carboxyhemoglobin
  • may have normal PaO2: CO concentration low enough to not affect PaO2 of dissolved O2
• in cyanide toxicity
  • increase venous Po2: narrowing of venous-arterial PaO2 gradient (venous hyperoxia differentiates between methemoglobinemia and cyanide toxicity)

Links to this note

• ICU intensive care unit

  • methemoglobinemia, cyanide, carbon monoxide blood gas differences

• toxic ingestions

  • methemoglobinemia, cyanide, carbon monoxide blood gas differences