Three cases of clinically significant inaccurate carboxyhemoglobin measurement.

Abstract

Background:

Clinicians often rely on measurement of carboxyhemoglobin (COHb) to confirm or rule out a diagnosis of carbon monoxide (CO) poisoning.

Methods:

We report two cases of false negative COHb in patients with CO poisoning and one case of false positive COHb in a patient without CO poisoning.

Results:

In the first case, a 20-year-old male developed headache, confusion, and near-syncope while operating a gasoline-powered pressure washer in an enclosed space. In the emergency department (ED), his COHb was 1.8%, but this level was disregarded, and he was referred for hyperbaric oxygen. His COHb just before hyperbaric oxygen was 4.1%, and later analysis of his blood collected at ED arrival revealed a COHb of 20.1%. The referral ED blood gas machine calibration and controls were within specification. In the second case, a 45-year-old male presented with several others to the ED with symptoms of CO poisoning after exposure at a conference. All others had elevated COHb levels, but his COHb was 2%. He was discharged but returned shortly with continued symptoms and requested his COHb be repeated. The repeat COHb was 17% (84 minutes after the first). After three hours of oxygen, his COHb was 7%. In the final case, an 83-year-old non-smoking male presented to an ED with breathlessness and tachypnea and was diagnosed with COVID-19 pneumonia. His COHb was 7.1%, but he reported living in an all-electric home. Another adult who lived with him and rode with him to the ED was asymptomatic and had a COHb of 3%. Later, COHb of 1.9% was measured from blood collected at ED arrival, and gas chromatography/mass spectrometry confirmed this result (2%).

Conclusions:

COHb levels are not always accurate. Clinicians should use clinical judgment to manage their patients, including rejecting laboratory values that do not fit the clinical situation.

• Authors: Lindell K Weaver, Kayla Deru, Buz Fletcher, Sara D Daniel
• Journal: Undersea & hyperbaric medicine : journal of the Undersea and Hyperbaric Medical Society, Inc (Undersea Hyperb Med) 2022 Second Quarter Vol. 49 Issue 2 Pg. 171-177 ISSN: 1066-2936 [Print] United States
• PMID: 35580484 (Publication Type: Case Reports, Journal Article)
• Copyright: Copyright© Undersea and Hyperbaric Medical Society.

Chemical References

• Carbon Monoxide
• Carboxyhemoglobin
• Oxygen

Topics

• Adult
• Aged, 80 and over
• COVID-19
• Carbon Monoxide
• Carbon Monoxide Poisoning (complications, diagnosis, therapy)
• Carboxyhemoglobin (analysis)
• Humans
• Male
• Middle Aged
• Oxygen
• Syncope
• Young Adult