Influence of pH on stored human platelets

BACKGROUND: During storage at room temperature, platelets (PLTs) undergo several changes, a process known as PLT storage lesion. The pH is one of the variables changing and has been suggested to be a good surrogate marker for the quality of PLT concentrates. It is unknown whether the pH decrease as such induces the PLT storage lesion or that the deterioration of the PLTs results in the pH decrease. In this study, the responses of PLTs to applied pH values were investigated. STUDY DESIGN AND METHODS: PLTs were washed three times in PLT additive solution (PAS-IIIM) and were resuspended in PAS-IIIM buffers with or without 30 percent plasma with different pH values over a range from 6.0 to 7.5 (at 37 degrees C). The PLTs were stored in 50-mL culture flasks at 22 degrees C. RESULTS: During 3 days of storage in 100 percent additive solution (AS), the extracellular pH did not affect in vitro quality measures. Both at the lower and at the higher end of the pH range, we observed an increased glycolytic flux, accelerated at Day 6. Also in the presence of 30 percent plasma, the effect of extracellular pH was very limited, but all variables indicated better PLT quality with stable values up to Day 6 of storage. CONCLUSIONS: We conclude that PLTs stored in 100 percent AS are able to cope with high and low pH values without a strong deterioration within 3 days. PLTs stored in 30 percent plasma-70 percent AS are more capable in dealing with different pH values than PLTs stored in AS and remained stable for 6 days. We suggest that the pH decrease is a result of the PLT storage lesion and not the cause