Citrate Solutions for Preservation of Fluid Blood

Solutions of sodium citrate have been used to prevent coagulation of blood for many years and these solutions have become increasingly important in preserving the fluid blood for transfer from one human being to another. The citrate solutions are also employed in various laboratory procedures, particularly in the preservation of leukocytes for study of phagocytosis. The present study was undertaken because of the suspicion that some untoward reactions observed following citrate transfusions might be related to the citrate. We obtained hermetically sealed ampules of the citrate solutions of 4 different manufacturers. All of these were perfectly clear. A test of the hydrogen-ion concentration of these 4 specimens revealed the following results: Table We also prepared some solutions in our own laboratory and found that one solution of sodium citrate, 2.5% in 0.6% sodium chloride, had a pH of 8.7, higher than that observed in any of the 4 commercial samples. We prepared a solution of citric acid, 2.5% in 0.6% sodium chloride, and found that this solution of citric acid had a pH of 1.17. A number of trial mixtures of citric acid and sodium citrate were then prepared and it was found that a mixture of 5 cc of the citrate with 0.03 cc of the citric acid gave an approximately neutral solution. The various solutions were then tested by mixing 1 cc of freshly drawn human blood with 4 cc of the undiluted citrate solution. These mixtures were incubated at 37°C for 20 hours, then placed in the refrigerator for 24 hours, and then left in the room for a week. The appearance of the preparation was recorded from time to time. At the end of a week there was very marked destruction of the red blood corpuscles with red discoloration of the supernatant liquid in those tubes in which the citrate solution of hydrogen-ion concentration 8.5, 8.1, and 8.2 had heen used. In the citrate of pH 8.0 the hemolysis was distinctly less.