Siemens Rapidlab 1200, Operator'S Manual, Page: 70 / 448

1-50 Rapidlab 1200 Operator’s Guide: System Overview and Intended Use
02087462 Rev. V
The percent of deoxyhemoglobin is determined using the following equation:
F HHb = c HHb / c tHb x 100
This is the fraction of hemoglobin that could deliver more oxygen to body tissues if
pulmonary oxygenation were improved.
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Methemoglobin
This is a fraction of hemoglobin that cannot deliver oxygen to body tissues and is elevated
in certain metabolic diseases.
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Methemoglobin (MetHb), which is sometimes known as
hemoglobin Hi, is hemoglobin whose iron is oxidized to its ferric state [FE(III)] and is
unable to bind oxygen. High methemoglobin concentrations, a condition called
methemoglobinemia, can produce hypoxia and cyanosis. Methemoglobinemia can be the
result of hereditary conditions or of exposure to toxic substances such as nitrates, nitrites,
aniline dyes and their derivatives, and topical anesthetics such as benzocaine.
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Infants
and other individuals with significant fetal hemoglobin concentrations show increased
susceptibility to methemoglobinemia because fetal hemoglobin converts to
methemoglobin more readily than adult hemoglobin.
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The methemoglobin reference
range for arterial or venous blood for a normal population is 0.0 to 1.5%.
The percent of methemoglobin is determined using the following equation:
F MetHb = c MetHb / c tHb x 100
Carboxyhemoglobin
Carboxyhemoglobin (COHb) is hemoglobin covalently bound to carbon monoxide.
Hemoglobin has over 200 times greater affinity for carbon monoxide than for oxygen.
Hemoglobin bound to carbon monoxide is unavailable for oxygen transport, and high
levels of carboxyhemoglobin result in hypoxia and cyanosis, which can be fatal.
The carboxyhemoglobin reference range for a normal population is 0.0 to 1.5% . While
the amount of carboxyhemoglobin in the blood of healthy nonsmokers is very small
(between 0.1% and 0.4%), smoking, air pollution, and occupational exposure to carbon
monoxide affect COHb levels.
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The percent of carboxyhemoglobin is determined using the following equation:
F COHb = c OHb / c tHb x 100