Preoperative thrombin generation is predictive for the risk of blood loss after cardiac surgery: a research article

BACKGROUND: In this study the value of thrombin generation parameters measured by the Calibrated Automated Thrombography for prediction of blood loss after cardiac surgery with cardiopulmonary bypass was investigated. METHODS: Thirty male patients undergoing first-time coronary artery bypass grafting were enrolled. Blood samples were taken pre-bypass before heparinisation (T1) and 5 min after protamine administration (T2). Thrombin generation was measured both in platelet-rich plasma and in platelet-poor plasma. Besides thrombin generation measurements, activated clotting time, haematocrit, haemoglobin, platelet number, fibrinogen, antithrombin, D-dimers, prothrombin time and activated partial thromboplastin time were determined. Blood loss was measured and the amount of transfusion products was recorded postoperatively until 20 hours after surgery. Patients were divided into two groups based on the median volume of postoperative blood loss (group 1: patients with median blood loss <930 ml; group 2: patients with median blood loss ≥930 ml). RESULTS: On T1, patients of group 2 had a significantly lower endogenous thrombin potential and peak thrombin (p<0.001 and p=0.004 respectively) in platelet-rich plasma, a significantly lower endogenous thrombin potential (p=0.004) and peak thrombin (p=0.014) in platelet-poor plasma, and a lower platelet count (p=0.002). On T2 both endogenous thrombin potential and peak thrombin remain significantly lower (p=0.011 and p=0.010) in group 2, measured in platelet-rich plasma but not in platelet-poor plasma. In addition, platelet number remains lower in group 2 after protamine administration (p=0.002). CONCLUSIONS: The key finding is that the Calibrated Automated Thrombography assay, performed preoperatively, provides information predictive for blood loss after cardiac surgery.