Methemoglobinemia in Emergency Medicine Workup

Author: David C Lee, MD; Chief Editor: Asim Tarabar, MD more...

Updated: Jul 27, 2011

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Laboratory Studies
Imaging Studies
Other Tests
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Laboratory Studies

The diagnosis of methemoglobinemia is confirmed by direct measurement of methemoglobin by a multiple wavelength co-oximeter.

Note the chocolate brown color of methemoglobinemia. Tube 1 and tube 2 have a methemoglobin concentration of 70%; tube 3, a concentration of 20%; and tube 4, a normal concentration.

Arterial blood gas:

Normal PaO₂ concentrations are usually found on analysis. Clinical cyanosis in the presence of normal arterial oxygen tensions is highly suggestive of methemoglobinemia ("saturation gap").
Oxygen saturations usually are inaccurate because they are calculated by using measured PaO₂ and pH levels.
The measured oxygen saturation is low.

Pulse oximetry:

Methemoglobin absorbs light at wavelengths that also absorb deoxyhemoglobin and oxyhemoglobin. Thus, methemoglobin interferes with the colorimetric testing that is used to obtain the percentage of oxyhemoglobin to deoxyhemoglobin.
Traditional pulse oximetry is inaccurate and unreliable in patients with high methemoglobin fractions. Traditional pulse oximetry of patients with low-level methemoglobinemia often reveals falsely low values for oxygen saturation, and it often reveals falsely high values in those with high-level methemoglobinemia.
Newer multi-wave length pulse oximeters can detect methemoglobinemia with an accuracy comparable to co-oximeters.
Cyanotic but relatively asymptomatic patients with low O₂saturation reading around 90% should raise suspicion for methemoglobinemia.

Imaging Studies

CT scanning of the head, when appropriate

Other Tests

Adjunctive laboratory tests include determining lactate levels and serum electrolyte levels. These may be helpful in determining the degree of tissue hypoxia and end-organ dysfunction.

Urine pregnancy tests should be performed in females of childbearing age.

Proceed to Treatment & Management

Contributor Information and Disclosures

Author

David C Lee, MD Research Director, Department of Emergency Medicine, Associate Professor, North Shore University Hospital and New York University Medical School

David C Lee, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American College of Medical Toxicology, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Coauthor(s)

Kathy L Ferguson, DO Attending Physician, Department of Emergency Medicine, New York Hospital of Queens, Queens, New York

Kathy L Ferguson, DO is a member of the following medical societies: American College of Emergency Physicians and American College of Medical Toxicology

Disclosure: Nothing to disclose.

Specialty Editor Board

Lance W Kreplick, MD, FAAEM, MMM Medical Director of Hyperbaric Medicine, Fawcett Wound Management and Hyperbaric Medicine; Consulting Staff in Occupational Health and Rehabilitation, Company Care Occupational Health Services; President and Chief Executive Officer, QED Medical Solutions, LLC

Lance W Kreplick, MD, FAAEM, MMM, is a member of the following medical societies: American Academy of Emergency Medicine and American College of Physician Executives

Disclosure: Nothing to disclose.

John T VanDeVoort, PharmD Regional Director of Pharmacy, Sacred Heart and St Joseph's Hospitals

John T VanDeVoort, PharmD is a member of the following medical societies: American Society of Health-System Pharmacists

Disclosure: Nothing to disclose.

Michael J Burns, MD Instructor, Department of Emergency Medicine, Harvard University Medical School, Beth Israel Deaconess Medical Center

Michael J Burns, MD is a member of the following medical societies: American Academy of Clinical Toxicology, American College of Emergency Physicians, American College of Medical Toxicology, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

John D Halamka, MD, MS Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center

John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Asim Tarabar, MD Assistant Professor, Director, Medical Toxicology, Department of Emergency Medicine, Yale University School of Medicine; Consulting Staff, Department of Emergency Medicine, Yale-New Haven Hospital

Disclosure: Nothing to disclose.

References

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Note the chocolate brown color of methemoglobinemia. Tube 1 and tube 2 have a methemoglobin concentration of 70%; tube 3, a concentration of 20%; and tube 4, a normal concentration.

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