[The effect of dilution and heparin on the blood gas analysis]

The effect of heparin on the measurement of blood gases is mainly caused by dilution, which substantially reduces the PCO2 and HCO3- values. Excess heparin will change the pH, PCO2 and 3- as a consequence of an alternation in H+ ionconcentration. The effect of dilution on electrolytes depends on the respective electrolyte concentration in diluent. Dilution reduces the glucose value, but to a higher degree as could be expected from a dilution effect. Heparin binds electrolytes and influences the results, especially the calcium ion. As a result of this investigation we recommend the 20IU or less heparin be used for multi-electrolyte determination with or without blood gas analysis, and that the dilution of sample be maintained at less than 5%. In other words, at least a 3ml or 2ml blood sample should be collected in a 5ml or 2ml glass syringe, the corresponding heparin concentration is 400kU/L or less.