Clinical - Hematologic
Dilutional Coagulopathy refers to the coagulopathy seen during massive transfusion for major trauma and/or hemorrhaging. Major trauma and hemorrhage cause coagulation abnormalities due to consumption of coagulation factors and platelets. Dilutional coagulopathy is due to dilution, along with consumption, of platelets during massive transfusion. Large volumes of crystalloid fluid used for resuscitation in these cases can also contribute to thrombocyptoenia. Packed red blood cells contain few platelets when stored for over 24 hours, and the platelets that packed red blood cells do contain are typically damaged and removed from circulation upon transfusion. Thrombocytopenia with platelet levels between 50,000 and 75,000/mm3 during massive transfusion should be treated with platelet concentrates. The number of units of packed red blood cells transfused does not accurately predict the degree of thrombocytopenia or the need for platelet transfusion.
Hypofibrinogenemia also becomes an issue early during major trauma and hemorrhage. Levels should be kept greater than 100 mg/dL with FFP or cryoprecipitate.
Low levels of Factor V and Factor VIII, the two most labile factors in packed red blood cells, are not thought to play a significant role in bleeding from massive transfusion. This is illustrated by the fact that only 5-20% of Factor V and 30% of Factor VIII are needed for adequate hemostasis during surgery. Over the course of 21 days in stored blood, Factor V decreases to 15% and Factor VIII decreases to 50%.
Of paramount importance during massive transfusion is avoidance of hypothermia. Hypothermic patients will continue to bleed despite adequate transfusion of packed red blood cells, FFP/cryoprecipitate, and platelets.