[Relationship between arginase activity and the storage time of packed red blood cells]

Given the increasing evidence regarding a relationship between packed red blood cells storage time and post-transfusion complications, we decided to determine the relationship between the arginase enzyme levels, biochemical parameters and haemolysis, with the storage time of transfused packed red blood cells.

We designed a prospective study that included 24 units of packed cells that had been consecutively transfused to patients of our hospital. After recording the storage time of each bag, 15 ml of blood was removed to determine arginase activity, biochemical parameters and haemolysis. A univariate analysis was performed on all the recorded parameters, and included those that were significant in the multiple regression model (P<.05).

The mean storage time was 18.6±6.1 days (range: 6-31 days), with a haematocrit of 59.8%±0.05%, a haemoglobin of 20.3±1.8 g/dl, a pH of 6.5±0.1, and an arginase activity of 140.1±124.0 mU/ml. A linear relationship was observed in the univariate analysis between the storage time and the pH (P=.001), the actual HCO(3) (P=.001), the haemolysis index (P=.035) and the SpO(2) (P=.01). Once adjusted for the confounding variables of the univariate model, a linear relationship was observed between the arginase activity and the storage time (P=.031).

Our study shows a directly proportional linear relationship between the storage time of packed red blood cells and their arginase activity. We suggest that these findings could be associated with the high incidence of complications after transfusion that may be directly proportional to their storage time.