Acid-base changes following exchange transfusion with citrated blood.

The acid-citrate-dextrose (ACD) solution used to preserve blood consists in effect of 2 parts trisodium citrate to 1 part citric acid. It forms a buffer solution such that the pH of bank blood less than 5 days old is, in our experience, 6 6 ± 0 * 2. It can be predicted, therefore, that infusion of ACD blood must lead to an initial acidosis, and that this will in due course be replaced by a metabolic alkalosis as citrate is metabolized to form 3 moles of sodium bicarbonate for each mole of trisodium citrate retained. In the individual subject, the rates at which these two effects operate will determine the severity of the initial acidosis, and the stage at which the later alkalosis develops.