Effects of priming volume reduction on allogeneic red blood cell transfusions and renal outcome after heart surgery.

INTRODUCTION: Excessive hemodilution during cardiopulmonary bypass (CPB) is associated with an increased rate of red blood cell (RBC) transfusion and acute kidney injury (AKI). Minimization of the oxygenator priming volume is a measure to contain hemodilution. In this study, we evaluated the new oxygenator, Sorin Inspire 6™, with respect to its ability to limit hemodilution, RBC transfusion rate and postoperative AKI rate. METHODS: A retrospective study on a consecutive series of 1,724 adult patients receiving heart surgery with CPB. Patients treated with the Inspire 6™ were assigned to the low priming volume oxygenator (LPVO) group (N=383) and patients treated with conventional oxygenators to the conventional group (N=1,341). Dynamic priming volume, time course of the hematocrit, RBC transfusions and AKI rate were compared between the groups. RESULTS: Priming volume was significantly (p=0.001) lower in the LPVO group (624±113 mL) vs. the conventional group (775±150 mL), with higher values of hematocrit during and after CPB. After correction for other confounders, patients in the LPVO group had a significantly lower RBC transfusion rate (odds ratio 0.68, 95% confidence interval 0.52-0.90, p=0.006) and AKI rate (odds ratio 0.55, 95% confidence interval 0.32-0.93, p=0.032). CONCLUSION: The Inspire 6™ oxygenator allows a significant containment of hemodilution during CPB, reducing the risk of RBC transfusions and postoperative AKI.

Transfusions during cardiopulmonary bypass: better when triggered by venous oxygen saturation and oxygen extraction rate.

During cardiopulmonary bypass (CPB), red blood cell transfusions may be required to correct dilutional anemia. The decision-making process for transfusions is usually based on the level of hemoglobin.This study investigates the hypothesis that oxygen-derived variables (mixed venous oxygen saturation, SvO(2), and oxygen extraction rate, O(2)ER) may be more reliable predictors of the efficacy of the transfusion. Thirty-six patients for 41 transfusion episodes during CPB were retrospectively analyzed. For each patient, oxygen-derived variables, including SvO(2) and O(2)ER, were measured before and after the transfusion. No changes in pump flow were allowed between the two measurements. The efficacy of transfusion was defined as an increase in SvO(2) of at least 5%. We identified 11 transfusion episodes leading to an efficacious SvO (2) increase. Factors associated with the efficacy of the transfusion were a low SvO(2) and a high O(2)ER. No association was found with hemoglobin values, unless for a trend for efficacy of transfusion in patients with very low (<6 g/dL) hemoglobin values. Cut-off values of 68% for SvO(2) and 39% for O(2)ER were predictive for the efficacy of red blood cell transfusions, with a high accuracy (c-statistics 0.856 and 0.848, respectively) and negative and positive predictive values exceeding 82%. In conclusion, SvO(2) and O(2)ER are better than the hemoglobin value for guiding the decision-making process of red blood cell transfusions to correct hemodilutional anemia during CPB.

Hypothermic cardiopulmonary bypass as a determinant of late thrombocytopenia following cardiac operations in pediatric patients.

BACKGROUND: Thrombocytopenia after cardiac operations is a common event in both adult and pediatric patients. Late thrombocytopenia (LTCP) is a less common event that is still without a well-recognized cause. This study explores the role of heparin-induced thrombocytopenia (HIT) and other factors (complexity of the operation, temperature management, and drug use) in determining LTCP. METHODS: We conducted an observational study of 63 consecutive patients aged <36 months operated with or without cardiopulmonary bypass (CPB). LTCP was defined as a platelet count <100,000 cells/microl or <50% of the pre-operative count at any point in time between post-operative days 5 and 10. A diagnostic test for heparin-platelet factor 4 (PF4) antibodies was performed in patients with LTCP. Other pre- and post-operative factors were investigated for their association with LTCP. RESULTS: LTCP occurred in 15 (24%) patients. No patient had positive heparin-PF4 antibodies. The lowest temperature on CPB was an independent predictor of LTCP, with a cut-off value at 29 degrees C (sensitivity 80%, specificity 70%). Other factors associated with LTCP were prolonged post-operative use of unfractionated heparin and milrinone. LTCP was associated with increased post-operative morbidity. CONCLUSION: LTCP was related to a combination of factors (operation severity, degree of hypothermia during CPB, prolonged use of unfractionated heparin, and milrinone). The individual contribution of each factor seems difficult to establish. However, the degree of hypothermia during CPB and drug-associated effects were identified. HIT could be excluded in all cases.

Closed, phosphorylcholine-coated circuit and reduction of systemic heparinization for cardiopulmonary bypass: the intraoperative ECMO concept.

Cardiopulmonary bypass with heparin-bonded circuits reduces systemic heparinization which is associated to a better clinical outcome in cardiac operations. In the present study, a novel biocompatible treatment, based on a phosphorylcholine coating without heparin, has been used to reduce systemic heparinization during cardiopulmonary bypass. Sixty patients underwent coronary revascularization with a fully phosphorylcholine-coated circuit. The circuit was entirely closed; suctions from the field were separated during the cardiopulmonary bypass time. A low systemic heparinization protocol based on half the loading dose of heparin (150 IU/kg) and a target activated clotting time of 320 seconds was applied. No thrombus formation inside the extracorporeal circulation circuit occurred; in-hospital mortality was absent. One patient (1.6%) had a postoperative myocardial infarction and 2 (3.3%) were surgically revised due to bleeding. Homologous blood transfusion rate was 11.6%, postoperative bleeding was 310 +/- 136 ml. If compared to patients treated with heparin-coated circuits and low systemic heparinization, these patients have better platelet count preservation and lower postoperative bleeding. The low thrombogenicity of phosphorylcholine-treated surfaces, despite the absence of surface-immobilized heparin, allows a safe reduction of systemic heparinization in the setting of an ECMO-like intraoperative cardiopulmonary - bypass. This intraoperative ECMO approach offers promising results in terms of clinical outcome after coronary revascularization operations.

Gabexate mesilate and antithrombin III for intraoperative anticoagulation in heparin pretreated patients.

Thirty patients scheduled for elective myocardial revascularization and having undergone preoperative heparin treatment have been admitted to this prospective, randomized study. The aim of the study was to test two different strategies for preserving circulating antithrombin III (AT-III) during cardiopulmonary bypass. Patients in the control group (group C, n = 10) were treated with a standard heparinization (300 IU/kg). Patients in group A (n = 10) received the same management plus two doses of purified antithrombin III (1000 IU each). Patients in group GA received 200 IU/kg heparin and a continuous infusion of heparin (100 IU/kg/h) and gabexate mesilate (2 mg/kg/h) plus the same dose of antithrombin III as group A. Both group A and group GA demonstrated a preservation of circulating AT-III when compared to group C; this effect was more pronounced in group GA. The total heparin dosage was less in group GA than in groups A and C. Purified AT-III administration is recommended in heparin pretreated patients; the addition of gabexate mesilate to this protocol decreases the heparin requirement and increases the AT-III preservation.