Methods
A single institution retrospective chart review of all consecutive patients from May 2020 to November 2021 who received PCC4 during cardiothoracic surgery were included. IRB approval to conduct the study was obtained. The institutional protocol is to use PCC4, a total dose of 30 units/kilogram immediately after completion of protamine administration for cases deemed an increased risk for bleeding and/or right heart failure including: heart transplantation, LVAD implantation, and/or aortic surgery (e.g. ascending aortic dissection repair), and for redo sternotomy cases (e.g. coronary artery bypass). Patients were monitored with standard bleeding assessment protocol to guide blood product resuscitation both intraoperatively and postoperatively with point of care laboratory monitoring, including point of care thromboelastogram and activated clotting time, as well as conventional laboratory monitoring including complete blood counts, and systemic coagulation panels (e.g. protime/international normalized ratio & partial thromboplastin time). For the purposes of establishing the blood transfusion threshold, products were administered based on the evidence of bleeding affirmed with laboratory results. Blood product selection was based on thromboelastogram in conjunction with clinical laboratory assessment (e.g. hemoglobin, platelets, and fibrinogen). As a general rule, packed red blood cells were considered for symptomatic need once hemoglobin was less than 7 grams per deciliter. The same criteria were used for fresh frozen plasma, an additional criteria being developed enzymatic hypocoagulability or clotting factor deficiency. Platelets were transfused for active bleeding with platelet count less than 50,000 per microliter and/or platelet dysfunction identified by thromboelastogram. Cryoprecipitate was transfused for active bleeding with evidence of fibrinolysis identified by thromboelastogram, as well as fibrinogen level less than 200 milligrams per deciliter.
Patients were validated for inclusion criteria. Data collection included:  surgery type, PCC4 timing and dose, type and quantity of blood transfusion within 72 hours postoperatively, patient demographics, baseline anticoagulation, postoperative chest tube output, incidence of right ventricular (RV) failure, hypersensitivity reactions, acute kidney injury, thromboembolic events, and mortality within 45 days of intraoperative PCC4. Primary assessment included surgery type, hourly chest tube output, and type and quantity of blood product administration. Secondary assessment included documentation of adverse events such as incidence of hypersensitivity reactions, right ventricular failure, multi-organ failure requiring renal replacement therapy or ECMO, thromboembolic events, and mortality.