A Micro-Technique for the Determination of the Acid-Base Balance of the Blood.

Abstract

An acid-base pipette has been developed for the determination of the acid-base balance of the blood on a single specimen of 0.1 cc. Finger blood is collected under oil saturated with a mixture of 5% CO₂—95% air. The pipette consists of a lower stem, A, graduated from 0.0 to 0.1 cc. in 0.005 cc. divisions, and a bulb, B, of 2 cc. volume and 11 mm. inside diameter (Fig. 1). The volume of 2 cc. is indicated by a calibration ring on the upper stem. It is important that the bulb B be made from the test-tubes similar to those containing the standards for the pH determination.

The use of the pipette is as follows: 0.1 cc. of blood is sucked into the pipette. This is followed by adjusted phenol-red saline solution up to the 2 cc. mark. The pipette is capped with a heavy rubber band and centrifuged. The volume of cells is noted, the pH is determined according to the method of Hastings and Sendroy 1 by comparison with standard tubes in a comparator block; the CO₂ content of the solution is determined by transferring the entire 2 cc. into the Van Slyke manometric blood gas apparatus and determining its CO₂ according to the method of Van Slyke and Neill. 2

A blank CO₂ determination is made on the reagents used. The data thus obtained, namely, pH, CO₂ content, and per cent cells, are sufficient to characterize the acid-base balance of the blood. A comparison of the results obtained by this method with those obtained by the standard macro-methods have shown that the percentage cells and pH are determined with the same accuracy in both methods.