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Methemoglobinemia: Differential Diagnoses & Workup

Author: David C Lee, MD, Research Director, Department of Emergency Medicine, Associate Professor, North Shore University Hospital and New York University Medical School
Coauthor(s): Kathy L Ferguson, DO, Attending Physician, Department of Emergency Medicine, New York Hospital of Queens, Queens, New York
Contributor Information and Disclosures

Updated: Jul 15, 2009

Differential Diagnoses

Acute Coronary Syndrome
Pediatrics, Anaphylaxis
Acute Respiratory Distress Syndrome
Pediatrics, Bacteremia and Sepsis
Anemia, Acute
Pediatrics, Dehydration
Anemia, Chronic
Pediatrics, Gastroenteritis
Anxiety
Pediatrics, Reactive Airway Disease
Asthma
Pediatrics, Respiratory Distress Syndrome
Congestive Heart Failure and Pulmonary Edema
Pediatrics, Reye Syndrome
Frostbite
Pediatrics, Rotavirus
Headache, Cluster
Pediatrics, Status Epilepticus
Headache, Migraine
Pediatrics, Tachycardia
Headache, Tension
Plant Poisoning, Glycosides - Coumarin
Hyperventilation Syndrome
Plant Poisoning, Herbs
Hyperviscosity Syndrome
Pulmonary Embolism
Labyrinthitis
Toxicity, Hydrocarbon Insecticides
Metabolic Acidosis
Myocarditis

Other Problems to Be Considered

Carbon monoxide poisoning
Ergot alkaloid poisoning
Sulfhemoglobinemia
Skin contamination with blue dyes causing skin discoloration

Workup

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 methemoglobinem...

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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Note the chocolate brown color of methemoglobinem...

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 O 2 saturation 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.

More on Methemoglobinemia

Overview: Methemoglobinemia
Differential Diagnoses & Workup: Methemoglobinemia
Treatment & Medication: Methemoglobinemia
Follow-up: Methemoglobinemia
Multimedia: Methemoglobinemia
References
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References

  1. Moore TJ, Walsh CS, Cohen MR. Reported adverse event cases of methemoglobinemia associated with benzocaine products. Arch Intern Med. Jun 14 2004;164(11):1192-6. [Medline].

  2. Ash-Bernal R, Wise R, Wright SM. Acquired methemoglobinemia: a retrospective series of 138 cases at 2 teaching hospitals. Medicine (Baltimore). Sep 2004;83(5):265-73. [Medline].

  3. Conkling PR. Brown blood: understanding methemoglobinemia. N C Med J. Mar 1986;47(3):109-11. [Medline].

  4. Ellenhorn MJ, Barceloux DG. Nitrates, nitrites, and methemoglobinemia. In: Medical Toxicology, Diagnosis and Treatment of Human Poisonings. 1988:844-851.

  5. Fitzsimons MG, Gaudette RR, Hurford WE. Critical rebound methemoglobinemia after methylene blue treatment: case report. Pharmacotherapy. Apr 2004;24(4):538-40. [Medline].

  6. Henretig FM, Gribetz B, Kearney T, Lacouture P, Lovejoy FH. Interpretation of color change in blood with varying degree of methemoglobinemia. J Toxicol Clin Toxicol. 1988;26(5-6):293-301. [Medline].

  7. Herman MI, Chyka PA, Butler AY, Rieger SE. Methylene blue by intraosseous infusion for methemoglobinemia. Ann Emerg Med. Jan 1999;33(1):111-3. [Medline].

  8. Howland MA. Methylene blue. In: Goldfrank's Toxicologic Emergencies. 8th ed. 2006:1746-1748.

  9. Price D. Methemoglobin inducers. In: Goldfrank's Toxicologic Emergencies. 8th ed. 2006:1734-1745.

  10. Umbreit J. Methemoglobin--it's not just blue: a concise review. Am J Hematol. Feb 2007;82(2):134-44. [Medline].

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Further Reading

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Keywords

methemoglobinemia, red blood cells, hemoglobin, methemoglobin levels, methemoglobin, hexose-monophosphate shunt pathway, diaphorase I, diaphorase II, heme group, iron, oxidation of iron, nicotinamide adenine dinucleotide, NADH, nicotinamide adenine dinucleotide phosphate, NADPH, methylene blue, cellular hypoxia, cyanosis, discoloration of skin, acidosis

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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.

Medical Editor

Lance W Kreplick, MD, MMM, FAAEM, FACEP, 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, MMM, FAAEM, FACEP is a member of the following medical societies: American Academy of Emergency Medicine and American College of Physician Executives
Disclosure: Nothing to disclose.

Pharmacy Editor

John T VanDeVoort, PharmD, Regional Director of Pharmacy, Sacred Heart & 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.

Managing Editor

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.

CME Editor

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, Department of Surgery, Section of Emergency Medicine, Yale University School of Medicine; Consulting Staff, Department of Emergency Medicine, Yale-New Haven Hospital
Disclosure: Nothing to disclose.

 
 
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