Postoperative Costs Associated With Outcomes After Cardiac Surgery With Extracorporeal Circulation: Role of Antithrombin Levels

Application of goal-directed therapy for the use of concentrated antithrombin for heparin resistance during cardiac surgery

The maintenance of anticoagulation in adult patients undergoing cardiopulmonary bypass is dependent upon a number of factors, including heparin concentration and adequate antithrombin activity. Inadequate anticoagulation increases the risk of thrombosis and jeopardizes both vascular and extracorporeal circuit integrity. The purpose of this study was to evaluate a goal-directed approach for the use of antithrombin in patients who were resistant to heparin. Following institutional review board approval, data were obtained from quality improvement records. A goal-directed protocol for antithrombin was established based upon heparin dosing (400 IU kg^-1 body weight) and achieving an activated clotting time of ⩾500 seconds prior to cardiopulmonary bypass. Two groups of patients were identified as those receiving antithrombin and those not receiving antithrombin. Outcome measures included activated clotting time values and transfusion rates. Consecutive patients (n = 140) were included in the study with 10 (7.1%) in the antithrombin group. The average antithrombin dose was 1,029.0 ± 164.5 IU and all patients had restoration to the activated clotting time levels. Patients in the antithrombin group were on preoperative heparin therapy (80.0% vs. 24.6%, p = 0.001). Prior to cardiopulmonary bypass the activated clotting time values were lower in the antithrombin group (417.7 ± 56.1 seconds vs. 581.1 ± 169.8 seconds, p = 0.003). Antithrombin patients had a lower heparin sensitivity index (0.55 ± 0.17 vs. 1.05 ± 0.44 seconds heparin^-1 IU kg^-1, p = 0.001), received more total heparin (961.3 ± 158.5 IU kg^-1 vs. 677.5 ± 199.0 IU kg^-1, p = 0.001), more cardiopulmonary bypass heparin (22,500 ± 10,300 IU vs. 12,100 ± 13,200 IU, p = 0.016), and more protamine (5.4 ± 1.2 vs. 4.1 ± 1.1 mg kg^-1, p = 0.003). The intraoperative transfusion rate was higher in the antithrombin group (70.0% vs. 35.4%, p = 0.035), but no differences were seen postoperatively. Utilization of a goal-directed algorithm for the administration of antithrombin for the treatment of heparin resistance is effective in patients undergoing cardiac surgery.

Dexamethasone Preconditioning in Cardiac Procedures Reduces Decreased Antithrombin Activity and Is Associated to Beneficial Outcomes: Role of Endothelium

Introduction: Decreased antithrombin (AT) activity in patients scheduled for cardiovascular surgery under cardiopulmonary bypass (CPB) is related to increased postoperative complications and hospitalization time. Indirect evidence suggests that glucocorticoids mitigate this decreased AT activity. To better understand the beneficial effects of AT we have analyzed: (i) the clinical relevance of acute dexamethasone (DX) administration before cardiac surgery on AT activity, (ii) the modulation by DX of AT expression in human endothelial cells (hECs), (iii) the activity of AT on migration and angiogenesis of hECs, or on angiogenesis of rat aorta. Methods: A retrospective cohort study in patients undergoing aortic valve replacement surgery was designed to evaluate the effect of DX administration on AT activity at five separate time points: preoperatively, during CPB, at intensive care unit admission and at 12 and 24 h post-intervention. We have analyzed also clinical differences in postoperative outcomes as safety and the length of stay in hospitalization. Changes in mRNA levels of AT induced by DX were determined by qRT-PCR in human coronary (hCEC), aorta (hAEC) and cardiac microvasculature (hCMEC) endothelial cells. AT activity on migration and angiogenesis were also assayed. Angiogenic growth of rat aortic rings incubated in Matrigel® was determined in presence and absence of AT. Results: The cohort comprised 51 patients in the control group and 29 patients in the group receiving dexamethasone. Preoperative DX supplementation reduced intraoperative decrease of AT activity (67.71 ± 10.49% DX treated vs. 58.12 ± 9.11% untreated, p < 0.001) that could be related to a decrease in the hospitalization time (7.59 ± 4.08 days DX treated vs. 13.59 ± 16.00 days untreated, p = 0.014). Treatment of hECs with 500 nM DX slightly increased AT expression. Incubation with 0.5 and 1 IU/mL of AT increased migration and angiogenesis in hCAECs and hAECs, but not in hCMECs. The same concentrations of AT potentiated angiogenic sprouting of new vessels from rat aorta. Conclusion: Preoperative DX supplementation could be an interesting procedure to avoid excessive decrease in AT levels during cardiac surgery. Positive outcomes associated with maintaining adequate AT levels could be related to its potential beneficial effect on endothelial function (migration and angiogenesis).