Experimental infusion phlebitis: importance of titratable acidity on phlebitic potential of infusion solution

The titratable acidity of infusion solutions has never been taken into account in infusion phlebitis. This study aims to clarify the importance of titratable acidity on the phlebitic potential of infusion solutions. Solutions with different titratable acidity (from 0.16 to 12 mEq/L) were infused into the ear veins of 6 rabbits for 6 h at 10 mL/kg/h, and the veins were later examined histopathologically. Even at pH 4.0, a commercial 10% glucose solution scarcely caused any changes because of its very low titratable acidity (0.16 mEq/L). A 10% glucose solution with its titratable acidity adjusted to 3 mEq/L (pH 4.3) with citrate and NaOH, however, caused phlebitic changes in all 6 rabbits, and adjusting the titratable acidity to 12 mEq/L (pH 4.4) increased the degree of phlebitis. On the other hand, a 10% glucose solution with a pH of 5.4 and a titratable acidity of 6 mEq/L caused slight phlebitic changes in half the rabbits. These results suggest that 1) the titratable acidity of infusion solutions is important to the phlebitic potential when the pH is low, 2) when the pHs are similar, the phlebitic potential of infusion solutions depend on the titratable acidity, and 3) the phlebitic potential of infusion solutions can not be estimated by pH or titratable acidity alone.