Determine the extent of carbon monoxide poisoning, toxicity; check on the effect of smoking on the patient; work up headache, irritability, nausea, vomiting, vertigo, dyspnea, collapse, coma, convulsions; work up persons exposed to fires and smoke inhalation.
Additional Test Information:
Carboxyhemoglobin is useful in judging the extent of carbon monoxide toxicity and in considering the effect of smoking on the patient. A direct correlation has been claimed between CO level and symptoms of atherosclerotic diseases, intermittent claudication, angina, and myocardial infarction. Exposure may occur not only from smoking but also from garage exposure, and from various motors. This test may be included when blood gases are ordered, when there is sufficient sample, and when such instrumentation is available.
Lavender-top (EDTA) tube or green-top (heparin) tube; submit original full, unopened tube
A morning specimen is not as good as one that is drawn in the late afternoon or evening, especially if the patient is an outpatient who may have occupational exposure (ie, policemen, firemen on day shifts, mechanics). CO tends to be cleared from the blood in hours. Treatment for carbon monoxide poisoning involves removal of the individual from the contaminated area and the administration of oxygen. The half-life of carboxyhemoglobin is five to six hours when the patient breathes room air; it is reduced to 1 to 11/2 hours when the patient breathes 100% oxygen. In severe cases, hyperbaric oxygen treatment at two to three atmospheres is recommended, if available. In the latter instance, the carboxyhemoglobin half-life is reduced to approximately 25 minutes. Hyperbaric oxygen therapy may reduce the incidence of neurological manifestations after exposure. Hyperbaric oxygen therapy has been recommended when the carboxyhemoglobin concentration exceeds 25%. Some have cautioned against basing decisions to institute hyperbaric oxygenation solely on the carboxyhemoglobin concentration owing to the inconsistent correlation between such a measurement and clinical severity.
Sampling time is end of shift for industrial exposure monitoring. Analytes with timing “end of shift” (meaning the last two hours of exposure) are eliminated rapidly with a half-life less than five hours. Such compounds do not accumulate in the body and, therefore, their timing is critical only in relation to the exposure period.
Refrigerate immediately after collection. Do not remove cap.