PAGE EXPIRES:  June 2000

SYNONYMS:  CO; carboxyhemoglobin

COMPONENT TESTS:  None (single test)

SCHEDULE:  Biweekly; turnaround time: 7 working days

SPECIMEN AND COLLECTION REQUIREMENTS:

• 2 mL whole blood (venous or arterial)
• Citrate anticoagulant
• Light blue top tube

CAUSES FOR REJECTION:  Improperly labeled specimen

STORAGE AND SHIPPING:  Refrigerate; do not remove cap; carboxyhemoglobin is stable.

USES:  Evaluation of exposure to carbon monoxide (fire, suicide attempt, etc.); evaluation of headache, dyspnea, coma, convulsions.

NORMAL VALUES:  < 5% nonsmokers

METHOD:  Narrow path spectrophotometric measurement at fixed wavelength

DESCRIPTION AND COMMENTS:  Should be drawn as soon after the last cigarette as possible, if only carboxyhemoglobin is to be tested; morning specimen not as good as one taken late in the afternoon or evening, especially for occupational exposure (mechanics, firemen, etc.); CO tends to be cleared from circulating blood in hours.

Potential toxic concentrations:

0 - 10%	No symptoms
10 - 20%	Slight headache, dyspnea on exertion
20 - 40%	Severe headache, nausea, confusion
40 - 60%	Syncope, convulsions, ataxia
60 - 80%	Coma, respiratory failure, death
>80%	Usually fatal

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