Ratios of Plasma and Platelets to Red Blood Cells in Surgical Patients With Acute Intraoperative Hemorrhage

Background The relationships between the ratios of transfused allogeneic blood products and clinical outcomes in patients with acute intraoperative hemorrhage are poorly defined. Methods To better define these ratios, we undertook a single-center, observational cohort study of all surgical patients (≥18 years) who received rapid transfusion defined by a critical administration threshold of 3 or more units of red blood cells (RBCs) intraoperatively within 1 hour between January 1, 2011 and December 31, 2015. Multivariable regression analyses were used to assess relationships between ratios of plasma to RBCs and platelets to RBCs at 3, 12, and 24 hours and clinical outcomes. The primary outcome was hospital mortality, with secondary outcomes of intensive care unit and hospital-free days. Results The study included 2385 patients, of whom 14.9% had a plasma-to-RBC ratio of 1.0+, and 47.6% had a platelet-to-RBC ratio of 1.0+. Higher plasma-to-RBC and platelet-to-RBC ratios were observed for patients who underwent cardiac, transplant, and vascular surgery and in patients with greater derangements in hemostatic laboratory values. Ratios did not differ by patient age or severity of illness. Higher ratios were not associated with improved clinical outcomes. Mortality differed by platelet-to-RBC but not plasma-to-RBC ratio, with the highest mortality observed with a platelet-to-RBC ratio of 0.1-0.9 at 24 hours (odds ratio, 3.34 [1.62-6.88]) versus no platelets (P= .001). Higher plasma-to-RBC ratios were associated with decreased hospital-free days, although differences in clinical outcomes were not significant after exclusion of patients receiving only RBCs without component therapies. Conclusions Transfusion ratios in surgical patients with critical intraoperative hemorrhage were largely related to surgical and hemostatic features rather than baseline patient characteristics. Higher ratios were not associated with improved outcomes.