A Review of Pathophysiology, Clinical Manifestations, And Therapeutic Management of Methemoglobinemia

Methemoglobinemia occurs when hemoglobin's iron is oxidized from ferrous (Fe2+) to ferric (Fe3+) state, resulting in impaired oxygen transport and potential tissue hypoxia. The condition manifests through inherited mutations affecting hemoglobin structure or enzymatic pathways, or through acquired causes including exposure to oxidizing agents and medications. Clinical presentations range from asymptomatic cases to severe manifestations like cyanosis, dyspnea, and life-threatening complications. Diagnostic challenges arise from the condition's ability to interfere with standard pulse oximetry readings, making specialized techniques like co-oximetry essential for accurate assessment. The primary therapeutic intervention involves methylene blue administration, which functions through the NADPH-dependent pathway to reduce methemoglobin levels. Treatment protocols require careful consideration of severity, underlying etiology, and individual patient factors, particularly G6PD status. Additional therapeutic options include ascorbic acid supplementation and supportive care measures. Recent molecular studies have enhanced the identification of genetic variants and improved understanding of drug-induced cases, leading to more targeted therapeutic approaches. Prevention strategies focus on identifying high-risk medications and environmental exposures. Early recognition and prompt intervention remain crucial for optimal patient outcomes, particularly in severe cases where methemoglobin levels exceed 30%.