Computer simulation of transfusion with different blood product ratios in modern massive transfusion protocols

Modern massive transfusion protocols call for early plasma and platelets to patients presenting with hemorrhagic shock. The packed red blood cell (PRBC):plasma:platelet ratio generally ranges from 1:1:1 to 3:1:1, but the ideal ratio remains controversial. We aimed to determine the effects of different resuscitation strategies and blood product ratios on hematocrit, platelet and fibrinogen concentrations (FC) during resuscitation. Assuming: pre-insult blood volume 5 L; hematocrit 0.4, FC = 100%, platelet count 400 × 10⁹/L; predetermined constant values for each blood product unit (volume, hematocrit, FC, platelet number); and transfusion rate to maintain euvolemia, we simulated different resuscitation strategies using a computer-based hemorrhage model. When crystalloids are administered to restore an acute 30% blood loss, the initial hematocrit, platelets and FC are adequate, and remain physiologic when further resuscitation is carried out with 1:1:1. Higher transfusion ratios increase the hematocrit at the expense of proportional drops in FC and platelets. When crystalloids and PRBCs (1500 mL) are administered to restore an acute 60% blood loss, the FC drops to 39%. Further resuscitation with 1:1:1 (but not with 2:1:1 or 3:1:1) increases the FC while maintaining the hematocrit and platelets within physiologic range. When blood products (1-3:1:1) are administered to restore an acute 60% blood loss, the initial hematocrit, platelets and FC are at adequate levels, but remain within physiologic range only when 1:1:1 (but not 2:1:1 or 3:1:1) is implemented for further resuscitation. Notably, platelet concentration consistently drops in all simulated scenarios reaching dangerously low levels particularly with high blood loss/transfusion rates and with higher transfusion ratios. The FC does not always drop by the same proportion with higher ratios probably because it is based on plasma concentration and is thus "cushioned" by the reduction in plasma volume as the hematocrit rises with higher transfusion ratios. In summary, computer simulation suggests that in non-severe shock hemorrhage, the differences between 1-3:1:1 transfusion ratios during initial resuscitation may be small. In severe shock, however, 1:1:1 results in the most physiologic hematocrit, FC and platelet concentration and is, therefore, desirable.