Postoperative care was performed in a polyvalent 24-bed intensive care unit (ICU), at a University hospital, Canary Islands (Spain). A total of 50 Caucasian patients undergoing elective CPB were considered for inclusion if they did not receive antifibrinolytic during or after the surgery, over a three-month period. Finally, we performed a nested case-control study of 26 patients who met the criteria. No patients had a history of hemostatic dysfunction, renal failure (Cr >2 mg/dL), chronic hepatopathy or immunosuppression. Before inclusion the participants had normal aggregation or coagulation functional test values (bleeding time, collagen/epinephrine and collagen/ADP closure time, prothrombin time, activated partial thromboplastin time and thrombin time). None of the patients received chronical immunosuppressive medications or other anti-inflammatory agents including acetyl salicylate acid or clopidogrel during the previous 5 days and the first 24 hours following intervention. This study was approved by our Hospital Ethics Committee. We obtained informed written consent from all patients for their inclusion in the study.

Demographic variables, comorbid conditions, perioperative clinical data and postoperative outcomes (duration of mechanical ventilation, Intensive Care Unit and hospital stay and mortality) were recorded. Core body temperature, biochemical determinations (hematology, coagulation, fibrinolysis and complement parameters) and hemodynamic parameters were recorded at four time points: before intervention, after surgery at 0 h and at 4 h and 24 hours post-intervention. In addition, we recorded blood loss measured by tube chest drainage and the amount of hemoderivatives used after intervention at the above time points and when chest tubes were removed (defined as total blood loss). Excessive bleeding was defined as blood loss >1 L over 24 hours after intervention. Surgical risk was calculated by parsonnet score and severity on admission by APACHE-II and SAPS II scores.

The same anesthetic procedure was used in all patients. All interventions were performed by the same surgical team. The extracorporeal circuit consisted of a hardshell membrane oxygenator (Optima XP, Cobe, Denver, Colorado or Quantum Lifestream International, Inc. TX USA), a Tygon™ extracorporeal circuit and a Medtronic™ Biopump centrifugal pump. Under 28–30°C hypothermia, the pump flow was adjusted to maintain a mean arterial pressure of >60 mmHg and a flow index of 2.2 l/min/m2. Myocardial protection was achieved using St. Thomas 4:1 sanguineous cardioplegia. The circuit was primed with 30 mg of heparin, followed by an initial dose of 3 mg/Kg and necessary doses to achieve and mantain an activated clotting time of 480 s. To reverse the effect of heparin, protamine was used based on blood heparin levels measured by Hetcon® (HMS.Medtronic™).

Serum leptin levels (normal range: