Biological and Clinical Relevance of Quantra Viscoelastic Hemostatic Assay in Hemorrhagic Cardiac Surgery

This observational study aims to assess the relevance of Quantra use in the setting of cardiac surgery patients presenting with acute bleeding in the operating room.

Hemorrhage is frequent in cardiac surgery. In the setting of per-operative acute bleeding, patient management and transfusions require a meticulous approach as both under-treatment and over-treatment can concur to morbidity and mortality. In this specific setting, the short timeframe of management usually does not allow usual laboratory tests (prothrombin time, activated clotting time, fibrinogen and platelets counts) to be integrated in the decision-making process. Viscoelastic hemostatic assays (VHA) such as Quantra might be relevant in this setting, owing to point-of-care bedside features.

As part of usual care for patients undergoing cardiopulmonary bypass for cardiac surgery at the Pitié-Salpêtrière Hospital, the investigators use Quantra viscoelastometric tests in various situations , including for per-operative hemorrhage management. Yet, it appears Quantra relevance has never been challenged in this population.

The investigators seek to determine whether in a population of patients presenting with significant hemorrhage in the operating room of cardiac surgery Quantra parameters (CT, CTH, FCS and PCS) are well-correlated to standard biology testing (prothrombin time, activated clotting time, fibrinogen and platelets count) and to transfusion thresholds.

Universal Definition of Perioperative Bleeding (UDPB) is a widely used quantification of bleeding in cardiac surgery. Nonetheless, most of its parameters of interest are assessed post-operatively and definition of acute bleeding during cardiac surgery lack. The investigators propose different bleeding definitions to assess hemorragic intra-operative events: 5 or more labile blood products transfused after protamine administration, and a modified UDPB definition to properly match significant per-operative bleeding events. The modified UDPB definition of interest will classify patients presenting with severe hemorrhage, patients presenting with massive hemorrhage as following:

Severe hemorrhage will be defined when one or more of the following occur:

• no sternal closure or use of a modified closure strategy (such as GoreTex closure)
• use of 5 to 10 blood products (packed red blood cells (RBC), fresh frozen plasma (FFP), platelets) during surgery
• more than 4.5g of fibrinogen cryoprecipitate or concentrate administered during surgery
• more than 50 UI/kg of human prothrombin complex (PPSB) administered during surgery
• three different hemostatic products within FFP, platelets, fibrinogen products and PPSB administered during surgery
• re-infusion of more than 1000mL of blood recovered from cell-salvage process

Massive hemorrhage will be defined as one or more of the following:

• use of more than 10 blood products (RBC, FFP, platelets) during surgery
• use of recombinant activated factor VII during surgery
• use of all hemostatic products available (FFP, platelets, PPSB, fibrinogen products).

This study is conducted in accordance with French law pending to observational studies. Non-opposition of patients is assessed prior to inclusion and data collection. Registry datas are extracted from the patients's medical records after anonymization.

Sample size has been estimated considering that 70 patients with acute bleeding in the operating room will be needed to properly assess correlation between Quantra and hemostasis biology in this population of interest. Considering a 15% incidence of bleeding in the hospital, 600 patients should be included overall to attain this objective. Yearly, 1200 to 1300 patients undergo cardiopulmonary bypass for cardiac surgery at the Pitié-Salpêtrière hospital. Quantra viscoelastometric assay and hemostasis biology are part of usual care and are usually tested when weaning cardiopulmonary bypass (i.e. after protamin antagonization) when risk factors for bleeding are present. Considering Quantra consumption from previous years (>1000/y in 2023 and 2024), although multiple testing is possible for some bleeding patients, the investigators estimate that about half of the patients are tested for both Quantra and hemostasis biology at the time of weaning from CPB. Hence, it is planned to include prospective patients undergoing cardiac surgery with CPB for 1 year.

Statistical analysis will be computed by the investigators. Results for categorical variables, expressed as number (%), will be compared using the χ² test or Fisher's exact test when appropriate. Continuous variables, expressed as mean (± standard deviation) or median [25th-75th percentile interquartile range (IQR)], will be compared using Student's t-test or Wilcoxon's rank-sum test, depending on data distribution. Missing datas will be excluded from statistical analysis. Correlations between Quantra parameters and Prothrombin Time, Activated Clotting Time, fibrinogen count and platelet counts will be analyzed by Spearman-Rank test. Statistical association between Quantra parameters and transfusion thresholds will be assessed by Receiver Operating Characteristics (ROC) curves and extraction of best thresholds with Youden points.