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CARDIOVASCULAR ANESTHESIOLOGY

An Assessment of Cardiopulmonary Bypass-Induced Changes in Platelet Function Using Whole Blood and Classical Light Transmission Aggregometry: The Results of a Pilot Study

Corinna Velik-Salchner, MD^*, Stephan Maier, MD^*, Petra Innerhofer, MD^*, Christian Kolbitsch, MD^*, Werner Streif, MD, Markus Mittermayr, MD^*, Michael Praxmarer, MSc, and Dietmar Fries, MD

From the Departments of *Anesthesiology and Intensive Care Medicine, Pediatrics, Innsbruck Medical University; Assign Data Management and Biostatistics, Innsbruck Austria; and Department of General and Surgical Critical Care Medicine, Innsbruck Medical University, Innsbruck, Austria.

Address correspondence and reprint requests to Corinna Velik-Salchner, MD, Department of Anesthesiology and Intensive Care Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020 Innsbruck, Austria. Address e-mail to corinna.velik{at}i-med.ac.at.

Abstract

BACKGROUND: In this study, we explored whether antiplatelet medications impair whole blood impedance aggregometry after cardiac surgery and cardiopulmonary bypass (CPB) compared with classical light transmission aggregometry (LTA).

METHODS: Multiplate® (M) assays measuring changes in electrical resistance as aggregation units over time, and LTA assays (% aggregation) induced by collagen (COL), adenosine diphosphate (ADP), or arachidonic acid were performed simultaneously using arterial blood samples obtained before induction of anesthesia, 15 min and 3 h after neutralization of heparin in 70 consecutive patients scheduled for elective coronary artery bypass grafting. Patients in Group A (n = 48) discontinued intake of antiplatelet drugs for at least 7 days and served as controls, patients in Group B (n = 11) received aspirin 100 mg/d and those in Group C (n = 11) aspirin 100 mg/d and clopidogrel 75 mg/d (dual antiplatelet therapy) until the day before surgery.

RESULTS: In patients without antiplatelet therapy, 15 min and 3 h after protamine a significant decrease in platelet aggregation was observed with all three agonists and both aggregation methods. In patients receiving aspirin alone, LTA-COL, LTA-ADP and M-ADP changed significantly over time, and ADP assays of both aggregation methods showed a significant decrease in platelet aggregation 15 min after protamine in patients receiving dual antiplatelet therapy. When calculating the areas under the receiver-operating characteristic curves for discrimination of antiplatelet agents, LTA-COL was able to discriminate between controls and patients receiving aspirin or dual antiplatelet therapy 15 min and 3 h after CPB and the M-ADP assay was able to discriminate between controls and patients receiving dual antiplatelet therapy 3 h after protamine.

CONCLUSION: Whole blood and classical LTA performed with all commonly used agonists enable detection of CPB-induced changes in platelet aggregation in patients not taking antiplatelet medication, whereas in patients receiving antiplatelet therapy, ADP-induced antiplatelet assays are preferable for detecting CPB-induced impairment of platelet aggregation.