Good Morning andWelcome Applicants

February 3, 2010

Methemoglobinemia• Normal Fe+2 to Fe3+

• Oxidation • Fe3+ is unable to

bind oxygen• Remaining Fe has

higher O2 affinity• Impaired O2 delivery

to tissues• Rare cause of

cyanosis

Methemoglobinemia• Hereditary

• NADH cytochrome b5 reductase deficiency• AR

• Hemoglobin M disease• AD• Structural alteration of alpha or beta

globin chains

Methemoglobinemia• Acquired

• Exogenous agents that increase methemoglobin formation• Topical anesthetic agents

• Benzocaine• Acute diarrhea and metabolic acidosis

• Babies 2-6 months• Abnormal absorption of nitrites

Methemoglobinemia• Presentation

• Cyanosis (8-12%)• 30-50%

• Dyspnea• Dizziness• Tachycardia• Fatigue• HA

Methemoglobinemia• Presentation

• 50-70%• Severe lethargy• Stupor

• >70%• Death

• Congenital• Asymptomatic

Methemoglobinemia• Suspicion

• Clinical cyanosis• Normal arterial pO2• “chocolate brown blood”• Pulse oximetry unreliable

Methemoglobinemia• Diagnosis

• Co-oximetry• Respiratory therapy• False positives with methylene blue with

some methods

• Genetic testing

Methemoglobinemia• Treatment - Acquired

• Recognition and discontinuation of offending agents

• Symptomatic or >20%• Methylene blue 1-2mg/kg

• May repeat 1 hr later (max dose 7mg/kg)• Reducing agents

• Ascorbid acid• Glutathione• Riboflavin

Methemoglobinemia• Treatment

• G6PD deficiency• May not respond to treatment

• Other• Hyperbaric oxygen• Exchange Transfusion

Methemoglobinemia• Lessons

• Always consider in differential diagnosis of cyanosis

• Caution with use of topical anesthetics• History

• Cyanosis• Blue nail beds• Blue lips

• Family History