Reducing the risk of hyperammonemia from transfusion of stored red blood cells.

Ammonia concentration increases in red cell units (RBCs) during storage. We measured absolute amounts of ammonia (AA) per unit serially in stored RBCs and before and after removal of the supernatant by volume reduction (VR) or washing. Ammonia increased 6.4-fold in untreated units over 31 days. VR decreased AA 3.7-fold, whereas washing decreased it 38-fold (p<0.0001). At least for certain patients, e.g., infants receiving large volume transfusions and patients in liver failure, it may be advisable to use RBCs as fresh as possible and to limit infusion (by VR or washing) of ammonia in the supernatant.