Umbilical blood gas analysis: II. Effects of sodium fluoride on changes during storage

Even when umbilical blood samples are kept on ice, their pH and blood gas values change during storage. The present study analyzes the effects of heparin and sodium fluoride (NaF) on these changes. At a concentration of 10 mg/ml, heparin significantly decreased all values; at a concentration of 5 mg/ml, it significantly decreased the pH and base excess values. Thus, the concentration of heparin used in microanalysis of blood should not exceed 2.5 mg/ml. NaF concentrations of 0.2 and 0.5 mg/ml reduced the decrease in pH after six hours (but not significantly) without causing changes themselves; but their effects on blood gas values were variable. A NaF concentration of 0.1--0.2 mg/ml is adequate to limit changes in most values during the storage of umbilical blood samples on ice for at least six hours.