Failing blood gas measurement due to methemoglobin forming hemoglobin variants: a case report and review of the literature.
BACKGROUND
We present a case of an arterial blood gas sample analysis from a 33-year old woman where no oximetry results could be obtained using the Radiometer ABL800 FLEX device. Clinical history of this patient learned that she was carrier of a methemoglobin forming hemoglobin variant type Hyde Park (HbM Hyde Park) and raised the question whether or not this variant could be the cause of the errors obtained during analysis.


METHODS
A literature search was performed, focusing on methemoglobin forming hemoglobin variants and their influence on oxygenation measurements. An overview of the currently described methemoglobin forming hemoglobin variants is also included.


CONCLUSIONS
In the presence of dyshemoglobins such as methemoglobin, techniques used to obtain parameters that reflect the patient oxygenation status, such as pulse oximetry and CO-oximetry can be influenced. In these cases, CO-oximetry is the preferred technique because it can compensate for this, in contrast to pulse oximetry. In case of the presence of methemoglobin originating from a hemoglobin variant, it is possible that CO-oximetry data cannot be calculated because the absorbance spectrum of this methemoglobin can differ from regular methemoglobin. Moreover, pulse oximetry devices are actually prone to erroneous results since pulse oximetry data will be calculated in these cases, but unreliable and should be avoided.


CONCLUSIONS
Methemoglobin forming hemoglobin variants are rare genetic mutations. However, they can possibly interfere with the calculation of CO-oximetry values. In these cases, pulse oximetry data should be avoided because they could lead to incorrect medical decisions.
a Laboratory Medicine , University Hospitals Leuven , Leuven , Belgium.
Toon
T
Schiemsky
b School of Life Sciences , Biomedical Research Institute, Hasselt University and Transnational University Limburg , Diepenbeek , Belgium.|c Laboratory medicine , Ziekenhuis Oost-Limburg , Genk , Belgium.
Joris
J
Penders
a Laboratory Medicine , University Hospitals Leuven , Leuven , Belgium.|d Department of Microbiology and Immunology , KU Leuven - University of Leuven , Leuven , Belgium.
Davy
D
Kieffer
D000328:Adult; D001784:Blood Gas Analysis; D003951:Diagnostic Errors; D019544:Equipment Failure Analysis; D005260:Female; D006449:Hemoglobin M / Q000032:analysis / Q000737:chemistry; D006454:Hemoglobins / Q000032:analysis / Q000737:chemistry; D006801:Humans; D008706:Methemoglobin / Q000032:analysis / Q000737:chemistry; D009154:Mutation; D010092:Oximetry
D006454:Hemoglobins; C056016:hemoglobin M Akita; D008706:Methemoglobin; D006449:Hemoglobin M
Blood gas analyzer; Failing oximetry; Hb Variant; HbM Hyde Park; Methemoglobin