A Rare Mechanism of Hypoxemia: A Case Report.

The leading causes of hypoxemia and acute respiratory failure commonly observed in the intensive care unit setting are ventilator/perfusion mismatch and intrapulmonary shunt. The main objective of the current report was to describe the treatment and the diagnostic procedures in a patient with methemoglobinemia. A 66-year-old woman arrived at the emergency department after suddenly losing coordination while walking and reported having experienced increased cough and sputum in the previous days. The patient, a current smoker with 35 pack-years, had comorbidities and chronic obstructive pulmonary disease, requiring long-term oxygen therapy. Extensive laboratory analyses revealed elevated methemoglobin (MetHb) levels, increasing from 10% upon admission to 25% of total hemoglobin (Hb), and the onset of post-surgical anemia (Hb 9.6 g/dL). In the present case, the hypoxemia was caused by an increase in MetHb levels, in addition to anemia due to surgical intervention and overhydration. Antibiotic and diuretic therapy for treating infection and right heart failure was effective, leading to a favorable postoperative course.