2015 年 41 巻 7 号 p. 455-462
We investigated the relation between the pH value of an infusion solution and the decrease of liquid level in a drip chamber in an infusion set. In the study, an infusion solution (not TPN solution) was admixed with sodium bicarbonate solution (Meylon® Injection) and dripped into an infusion set. It was found that the liquid level in the drip chamber was decreased sharply when the pH value of the infusion solution became smaller than 7. Furthermore, with regard to infusion solutions that showed a large decrease of liquid level, the concentration of CO2 in the drip chamber at the start of drip infusion was approximately 2 v/v% in the conventional procedure where no preventive measures were attempted for such decrease, while its concentration was as high as 15 v/v% when preventive measures were attempted for such decrease. As compared with the conventional procedure, there was no difference in the CO2 concentration at 2 hours of drip infusion. These results indicate that the effect of prevention of decreasing the liquid level in the drip chamber was confirmed by changes in the CO2 concentrations in a drip chamber. The concentration of H2CO3 involved in the decrease of liquid level in the drip chamber was approximately 10% of the total concentration of H2CO3, which was confirmed by measuring H2CO3 concentrations at the end of an infusion set when the infusion solution admixed with Meylon Injection, which showed the largest decrease of liquid level in the drip chamber, was dripped into an infusion set.