Education Program



Disclosure:

Herrick: No relevant conflicts of interest to declare.

Disturbances in the normal physiologic process
of continuous methemoglobin formation followed by its reduction to hemoglobin
result in methemoglobinemia, which impairs oxygen delivery, sometimes
discernible as cyanosis. When cyanosis occurs, the differential diagnosis is
broad, and etiologies vary from acutely life-threatening to essentially
compensated and harmless; therefore, evaluations can easily burgeon into
extensive, costly endeavors and unnecessary treatments.  This educational session will explore the
evidence for best practices for assessing, diagnosing, and managing patients
with cyanosis and hypoxia, and when to consider methemoglobinemia. Laboratory
diagnostic patterns will be compared. Inherited disorders, including M-hemoglobin
variants and mutations in CYB5R3, and acquired disorders that carry the
risk of acute toxicity will be discussed. Lastly, management strategies
regarding these conditions will be reviewed.Dr. Jennifer L. Herrick will discuss the
diagnosis of methemoglobinemia and sulfhemoglobinemia in a reference laboratory
setting. Laboratory test result patterns and possible pitfalls will be
highlighted regarding acquired and inherited conditions, as well as treatment
artifacts.Dr. Josef T. Prchal will focus on inherited
methemoglobinemias, which result from impaired reductive mechanisms. He will
review methemoglobin structure, formation, and reduction to provide a basis for
understanding the causes of inherited methemoglobinemias. The known genetic
causes of methemoglobinemia, their diverse phenotypes and molecular biology,
diagnostic strategies, and management will be discussed. Dr. Noemi Roy will provide a structured
approach to acquired methemoglobinemia, organized around four questions: who to
suspect, why it happens, how to diagnose, and what to do. She discusses the
populations and exposures that should raise suspicion, including dapsone and
other chronic oxidant medications, rasburicase prescribing, peri-procedural
topical anaesthetics, and recreational nitrite use. A mechanism-based framework
that predicts each agent's clinical time course will be presented.