Purpose: Ringer's lactate (RL) may be preferable to normal saline (NS) for large volume resuscitation. Authorities recommend against its mixture with packed red blood cells (PRBC) due to a theoretical risk of clotting. The purpose of this study was to test whether RL, as compared with NS, leads to a risk of clotting when used to dilute AS-3 preserved PRBC in a clinically relevant model.
Methods: Following Ethics Board approval, eight units of unused, unexpired AS-3 preserved PRBC were obtained. Four sets of two parallel studies were performed, comparing RL with NS as the diluent for PRBC. The mixtures were infused using gravity flow through standard blood filter tubing and fluid warmer, to simulate an intraoperative blood transfusion. A series of progressively more dilute samples was collected. These were filtered and analyzed macroscopically, then using enzyme-linked immunosorbent assay to quantify the amount of F1+2 (the breakdown products of thrombin generation).
Results: No filters in any of the NS and RL mixtures contained evidence of clot or debris. In the NS group, the F1+2 levels ranged from 2.7 to 38.0 pmol x L(-1). In the RL group, the F1+2 levels ranged from 3.2 to 289.7 pmol x L(-1). All of these values were below the physiologic levels determined in previous studies.
Conclusion: In this simulation of intraoperative blood transfusion, RL did not lead to visible or molecular evidence of activation of the clotting cascade. The current study challenges recommendations that AS-3 PRBC should not be mixed with RL for rapid transfusion.