Clinical Studies on the Buffer Capacity of the Blood

Abstract

The authors review briefly changes occurring in blood reaction and factors maintaining the buffer action of the blood. In usual laboratory tests which assist in evaluating fluid balance, the bicarbonate and protein determinations are able to account for only about 21% of the total buffer capacity of the blood. Determinations of the total buffer capacity were made in 30 cases involving thoracic surgery. A medical series consisting of 15 patients with various diseases associated with anemia was used for comparison. Blood pH was determined potentio-metrically, by comparing the pH of the blood solution with the pH of a known buffer solution. The potentiometer was sensitive to 0.01 pH unit. When dissociation constants and concentrations of the components of the acid-base mixture are known, the buffer capacity at different pH levels can be calculated theoretically by van Slyke''s formula. In the surgical series, the buffer capacity of blood usually declined postoperatively. It was lowest 2-10 days after operation. In a notable proportion of cases (6 cases) the fall was over 40% of the original value In 9 cases it was over 25%. The great significance of the hemoglobin concentration and blood transfusions in maintaining the buffer capacity stable is discussed. It seems that during the 3d postoperative week the buffer capacity values begin to rise even when hemoglobin values are relatively low. The values for the buffer capacity in the comparative medical series were also relatively higher than would be presumed on the basis of the surgical series and by mathematical calculations. Numerous determinations of blood alkali reserve and the plasma proteins showed no parallelism with changes in the blood buffer capacity values. The importance of the buffer capacity in the maintenance of stability of the pH level of the blood is stressed, determination of this capacity for evaluation of the stability of the blood pH is recommended.