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Interpretive Handbook

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Test 8649:
Carbon Monoxide, Blood

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Carbon monoxide (CO) poisoning causes anoxia, because CO binds to hemoglobin with an affinity 240 times greater than that of oxygen, thus preventing delivery of oxygen to the tissues. Twenty percent saturation of hemoglobin induces symptoms (headache, fatigue, dizziness, confusion, nausea, vomiting, increased pulse, and respiratory rate). Sixty percent saturation is usually fatal. This concentration is reached when there is 1 part CO per 1,000 parts air.

 

Carboxyhemoglobin diminishes at a rate of about 15% per hour when the patient is removed from the contaminated environment.

 

The most common cause of CO toxicity is exposure to automobile exhaust fumes. Significant levels of carboxyhemoglobin can also be observed in heavy smokers. Victims of fires often show elevated levels from inhaling CO generated during combustion. Susceptibility to CO poisoning is increased in anemic persons.

Useful For Suggests clinical disorders or settings where the test may be helpful

Verifying carbon monoxide toxicity in cases of suspected exposure

Interpretation Provides information to assist in interpretation of the test results

Normal concentration:

<7% (1% lower limit of detectability)

<15% (heavy smoker)

Toxic concentration: > or =20%

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

No significant cautionary statements

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Normal: <7%

1% (lower limit of detectability)

<15% (heavy smoker)

Toxic concentration: > or =20%

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Lovejoy FH Jr, Linden CH: Acute poison and drug overdosage: carbon monoxide. In Harrison's Principles of Internal Medicine. Twelfth Edition. Edited by JD Wilson, E Braunwald, KJ Isselbacher, et al. New York, McGraw-Hill Book Company, 1991, pp 2171-2172

2. Carbon monoxide  intoxication--a preventable environmental health hazard. Mor Mortal Wkly Rep 1982;31:529-531