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Case Report | Emergency Medicine | Volume 15 Issue 5, May 2026 | Pages: 1903 - 1904 | India
The Saturation Gap Puzzle: A Diagnostic Challenge in the Emergency Department
Abstract: Background: Methemoglobinemia is an uncommon disorder that can significantly affect the interpretation of oxygenation parameters. The coexistence of additional causes of hypoxemia may further complicate clinical assessment and decision-making. Recognition of discrepancies between pulse oximetry, arterial blood gas analysis, and the patient's clinical status is essential for accurate diagnosis. Case Presentation: A 28-year-old woman presented to the emergency department with headache and severe hypertension. Physical examination revealed central cyanosis with unexpectedly low pulse oximetry readings. Arterial blood gas analysis demonstrated a marked discrepancy between oxygen saturation measurements and the patient's relatively preserved clinical condition. Co-oximetry identified methemoglobinemia, while concurrent chronic kidney disease with pulmonary congestion contributed additional hypoxemic burden. Despite profoundly abnormal oxygenation parameters, the patient showed no evidence of tissue hypoxia. Conclusion: Methemoglobinemia can produce significant discrepancies between pulse oximetry and arterial oxygen saturation measurements, particularly when additional causes of hypoxia coexist. Clinical assessment, co-oximetry, and evaluation for tissue hypoxia are essential for accurate interpretation of oxygenation status. Clinicians should exercise caution when relying solely on pulse oximetry in such patients.
Keywords: Methemoglobinemia, Saturation Gap, Pulse Oximetry, Co-oximetry, Hypoxemia, Cyanosis, Chronic Kidney Disease, Emergency Medicine, Tissue Hypoxia, Diagnostic Challenge
How to Cite?: Dr. Simran Kumar, Dr. Pooja Verma, "The Saturation Gap Puzzle: A Diagnostic Challenge in the Emergency Department", Volume 15 Issue 5, May 2026, International Journal of Science and Research (IJSR), Pages: 1903-1904, https://www.ijsr.net/getabstract.php?paperid=SR26530114914, DOI: https://dx.dx.doi.org/10.21275/SR26530114914