Blood Gasses Flashcards
1
Q
Bicarbonates (total carbon dioxide)
A
- Total carbon dioxide is clinically measured by:
Acidification of serum or plasma sample and measurement of carbon
dioxide released
Alkalinization and measurement of total bicarbonates
2
Q
Determination of serum/plasma CO2
A
- Acidifying the sample converts the various forms of CO2 in plasma to
gaseous CO2 by dilution with an acid buffer. - Alkalinizing the sample converts all CO2 and carbonic acid to HCO3−
- In indirect electrode-based methods (ISE) the amount of released gaseous
CO2 after acidification is determined by a PCO2 electrode - The enzymatic reactions (after alkalinization) lead to decrease in
absorbance of NADH at 340nm in proportion to total carbon dioxide content.
2
Q
Specimen requirements
A
- Same sample types used for Na+ or K+ may be assayed for carbon dioxide
concentration, samples must be analyzed promptly - Samples must be centrifuged in unopen tubes (air contains less CO2 than
does plasma, and CO2 will escape from the specimen into the air, of up to
4 to 5 mmol/L in 1 hour)
3
Q
Reference intervals and Clinical significance
A
- Total carbon dioxide in adults is 22 to 28 mmol/L, instrument dependent
- Alterations in bicarbonates is a sign of acid-base imbalance
