Methemoglobinemia: Difference between revisions
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**50-60%: myocardial ischemia, dysrhythmias, depressed mental status, seizure | **50-60%: myocardial ischemia, dysrhythmias, depressed mental status, seizure | ||
**>70%: usually lethal | **>70%: usually lethal | ||
==Differential Diagnosis== | |||
==Diagnosis== | ==Diagnosis== | ||
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==See Also== | ==See Also== | ||
[[Toxidromes]] | *[[Toxidromes]] | ||
== | ==References== | ||
[[Category:Tox]] | [[Category:Tox]] | ||
Revision as of 13:12, 10 June 2015
Background
- Methemoglobin refers to ferric form of Hb (Fe3+) that is unable to bind O2
- Caused by exposure to oxidizing agent (benzocaine, CN kit, antimalarials)
- Suspect in any pt whose cyanosis does not respond to supplemental O2
Clinical Features
- Levels
- Pts with anemia or preexisting cardiopulmonary disease will show symptoms sooner
- <20%: asymptomatic, gray-blue cyanosis
- 20-30%: anxiety, HA, weakness, light-headedness, tachycardia
- 50-60%: myocardial ischemia, dysrhythmias, depressed mental status, seizure
- >70%: usually lethal
Differential Diagnosis
Diagnosis
- Co-oximetry
- SpO2 will initially be falsely elevated until MetHb >30% (SpO2 will then fall to 80-85%)
- "Chocolate brown" color of blood
Treatment
- Methylene Blue
- Reserved for symptomatic pts or asymptomatic pts w/ MetHb >25%
- 1-2mg/kg Methylene Blue IV over 5min; repeat dose if needed
- Improvement seen w/in 20min