Impact of Transfused Citrate on Pathophysiology in Massive Transfusion

This narrative review article seeks to highlight the effects of citrate on physiology during massive transfusion of the bleeding patient. DATA SOURCES: A limited library of curated articles was created using search terms including “citrate intoxication,” “citrate massive transfusion,” “citrate pharmacokinetics,” “hypocalcemia of trauma,” “citrate phosphate dextrose,” and “hypocalcemia in massive transfusion.” Review articles, as well as prospective and retrospective studies were selected based on their relevance for inclusion in this review. STUDY SELECTION: Given the limited number of relevant studies, studies were reviewed and included if they were written in English. This is not a systematic review nor a meta-analysis. DATA EXTRACTION AND SYNTHESIS: As this is not a meta-analysis, new statistical analyses were not performed. Relevant data were summarized in the body of the text. CONCLUSIONS: The physiologic effects of citrate independent of hypocalcemia are poorly understood. While a healthy individual can rapidly clear the citrate in a unit of blood (either through the citric acid cycle or direct excretion in urine), the physiology of hemorrhagic shock can lead to decreased clearance and prolonged circulation of citrate. The so-called “Diamond of Death” of bleeding—coagulopathy, acidemia, hypothermia, and hypocalcemia—has a dynamic interaction with citrate that can lead to a death spiral. Hypothermia and acidemia both decrease citrate clearance while circulating citrate decreases thrombin generation and platelet function, leading to ionized hypocalcemia, coagulopathy, and need for further transfusion resulting in a new citrate load. Whole blood transfusion typically requires lower volumes of transfused product than component therapy alone, resulting in a lower citrate burden. Efforts should be made to limit the amount of citrate infused into a patient in hemorrhagic shock while simultaneously addressing the induced hypocalcemia.