ACD was developed into CPD (citrate-phosphate-dextrose) in 1957, a version with phosphate added intended to reduce phosphate leakage from red blood cells. It does not improve shelf life appreciably, but patient recovery is improved.
In 1957, ACD was modified into CPD (citrate-phosphate-dextrose), a formulation that included phosphate to reduce the loss of phosphate from red blood cells. While it doesn't substantially extend shelf life, it does improve patient outcomes.