Simultaneous determination of pH, CO2 content, and cell volume in 0.1 ml. aliquots of cutaneous blood; a modification of the Shock and Hastings technic.

IN1934 SHOCK AND HASTINGS (1) described the construction and use of a micropipet, by means of which blood in 0.1 ml. aliquots could be used for the simultaneous determination of pH, 002 content, and red cell volume. In this method the blood in two pipets was diluted to 2.0 ml. with saline-phenol red solution, centrifuged, and used first for the determination of hematocrit value, second for the colorimetric determination of pH by visual comparison with previously prepared standards, and last, for the determination of CO2 content in whole blood in the manometric Van Slyke apparatus. One or two additional pipets were filled with blood and 0.9% NaC1 to serve as color blanks. A sample size of 0.5 ml. or less is thus sufficient for the determination of all three factors in duplicate, and cutaneous blood may therefore be utilized as an easily obtainable substitute for arterial blood. The method is particularly useful for the study of acid-base balance in infants. Although the original method is suitable for most clinical purposes, the