Carbonate In Serum

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Contents 1 Reference-interval 2 Principle 3 Clinical-significance 4 Increases 5 Decreases 6 Specimen 7 More General Terms 8 Additional Terms 9 References

Reference-interval

• Male & Female: 22- 30 mmol/L

Principle

• The Kodak Ektachem Clinical Chemistry Slide (ECO2) is a dry multilayered, self-contained analytical element coated on a clear polyester support.
  
• A 10 uL drop of sample deposited on the slide is evenly distributed by the spreading layer into the underlying layers. The high pH in the spreading layer ensures that essentially all CO2 in the sample is the bicarbonate form & the acetazolamide inhibits carbonic anhydrase. Bicarbonate diffuses to the gel layer & is used to carboxylate phosphoenolpyruvate in the presence of phosphoenol- pyruvate carboxylase to form oxaloacetate and inorganic phosphate. The final reaction involves the malate dehydrogenase-catalyzed oxidation of NADH & reduction of oxaloacetate to produce NAD+ & malate.
  
• Following addition of sample, the slide is incubated at 37 C. The concentration of CO2 in the sample is determined by measuring the absorbance of the unreacted NADH by reflectance spectrophotometry after a five-minute incubation.
  
• The following reaction sequences are involved:
  

*                               Phosphoenol 
*                               pyruvate 
*                               Carboxylase 
* HCO3- + Phosphoenolpyruvate   --------->   Oxaloacetate + HPO4=  
* 
*                            Malate 
*                            Dehydrogenase 
* Oxaloacetate + NADH + H+   ------------->   Malate  +  NAD+ 
*

Clinical-significance

• One of the important buffer systems that maintains the pH of the blood is the carbonic acid- bicarbonate buffer system. Total CO2 (i.e., bicarbonate plus dissolved CO2) measurement are used together with other clinical & laboratory information for the evaluation of acid-base disorders.

Increases

• respiratory acidosis
• metabolic alkalosis
• excessive alkali intake

Decreases

• metabolic acidosis
• compensated respiratory alkalosis
• renal disorders where H+ ions cannot be excreted

Specimen

• No special patient preparation necessary.
  
• Sample preparation: Collect specimen by standard venipuncture technique. Heparin may be used as an anticoagulant for plasma specimens; DO NOT use citrate or EDTA. DO NOT DRAW SPECIMEN FROM ARE RECEIVING AN INTRAVENOUS TRANSFUSION.
  
• SPECIAL PRECAUTIONS:
  
• Handle specimens anaerobically to avoid loss of CO2. Remove serum promptly from the clot & analyze as soon as possible. Keep specimens in a tightly stoppered container with a minimum of dead air space. Sample cups should be capped. CO2 values may be lowered by as much as 6 mmol/L when uncapped specimens are exposed to the air for one hour. If analysis is not performed immediately, specimens should be tightly capped & refrigerated at 2-8 C.
  
• minimum sample size 0.5 milliliter with an optimum size of 1.0 milliliters or larger.

More General Terms

• general chemistry test

Additional Terms

• HCO3- (bicarbonate)

References

1. Kodak Ektachem 700 Analyzer Operator's Manual, Kodak Clinical Products, Rochester, New York.
2. Kodak Ektachem Slide Package Inserts, Kodak Clinical Products Rochester, New York.
3. Kodak Ektachem Training Manual, Kodak Clinical Products, Rochester, New York.

carbonate (HCO3-, CO3=) in serum