CO-Oximetry Interference in a Patient with Dyspnea Refractory to Oxygen Therapy

Binns, Thomas C; Koch, Christopher D.; Durant, Thomas J S; El-Khoury, Joe M.

doi:10.1093/jalm/jfab071

Cited by 1 publication

(1 citation statement)

References 9 publications

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“…The algorithm assumes that the blood sample contains predominantly normal haemoglobin A, although correction for the presence of fetal haemoglobin is possible. Structural haemoglobin variants (eg, haemoglobin M-Boston),15 certain dyshaemoglobins (eg, sulfhaemoglobin)16 and small molecules (eg, hydroxocobalamin,17 methylene blue)18 have all been reported to interfere with the internal algorithm and thereby lead to suppressed co-oximetry results with error flags. The analytical specificity for methaemoglobin is provided in the form of interference testing data but is not reported.…”

Section: Discussionmentioning

confidence: 99%

Methaemalbumin: a diagnostic surrogate for methaemoglobinaemia and treatment with red cell exchange in a patient with thalassaemia

et al. 2023

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A man in his 30s with alpha thalassaemia (four-alpha globin gene deletion) presented with 1 week of shortness of breath and 1 month of general malaise. Pulse oximetry monitoring revealed low peripheral oxygen saturation of approximately 80% despite maximal high-flow nasal cannula oxygen (fractional inspired oxygen 1.0–60 L/min flow). Arterial blood gas samples were chocolate brown in colour, with a low arterial partial pressure of oxygen of 197 mm Hg. This large oxygen saturation gap raised suspicion for methaemoglobinaemia. However, the patient’s co-oximetry results were suppressed by the blood gas analyser and delayed a definitive diagnosis. A methaemalbumin screen was sent instead, which was positive at 65 mg/L (reference interval: <3 mg/L). Treatment with methylene blue was initiated but did not result in complete resolution of cyanosis. This patient had been red cell exchange dependent since childhood for thalassaemia. Therefore, an urgent red cell exchange was initiated overnight, leading to an improvement in symptoms and interpretability of co-oximetry results. This resulted in rapid improvement without residual sequelae or complications. We conclude that a methaemalbumin screen can be used as a surrogate test for prompt confirmation of diagnosis in lieu of co-oximetry in cases of severe methaemoglobinaemia or in cases with underlying haemoglobinopathy. Red cell exchange can allow prompt methaemoglobinaemia reversal, especially if methylene blue is only partially effective.

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