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Platelet Dysfunction as Measured by a Point-of-Care Monitor is an Independent Predictor of High Blood Loss in Cardiac Surgery

Orlov, David MD*; McCluskey, Stuart A. MD, FRCPC, PhD*; Selby, Rita MD, FRCPC; Yip, Paul PhD, FCACB; Pendergrast, Jacob MD, FRCPC; Karkouti, Keyvan MD, FRCPC, MSc*§‖

doi: 10.1213/ANE.0000000000000054
Cardiovascular Anesthesiology: Research Report

BACKGROUND: Excessive bleeding carries a heavy burden of illness in cardiac surgery. Although platelet dysfunction is considered to be an important cause, it is not routinely measured. Our objective was to explore the relationship between platelet dysfunction and blood loss in cardiac surgery.

METHODS: In 100 consenting patients undergoing cardiac surgery requiring cardiopulmonary bypass, platelet function was measured before, during, and after bypass with a point-of-care device that compares platelet counts before and after exposure to an agonist. Clinicians were blinded to the results of testing. Patients whose calculated blood loss was part of the highest quartile for the cohort were classified as having had high blood loss. The independent relationship between platelet function and high blood loss was measured with the aid of multivariable Poisson regression modeling (with a robust error variance) that controlled for patients’ overall risk of high blood loss.

RESULTS: Calculated blood loss was negatively skewed with a median of 798 mL (25th and 75th percentiles of 380 and 1775 mL). Patients whose blood loss exceeded 1770 mL were classified as having had high blood loss, and 25 patients met this criterion. There was 1 death in the high blood loss group unrelated to hemorrhage. After adjusting for bleeding risk, each 10 × 109/L increase in collagen-activated functional platelet count during rewarming and postprotamine, respectively, was associated with a relative risk of 0.89 (95% confidence interval, 0.82–0.97; P = 0.006) and 0.87 (95% confidence interval, 0.78–0.98; P = 0.02) for high blood loss.

CONCLUSIONS: Platelet dysfunction, as measured by a point-of-care method during rewarming and postprotamine, is independently associated with high blood loss in cardiac surgery. Additional studies are needed to determine whether the incorporation of this assay into blood management algorithms might help rationalize blood transfusion therapy, potentially reducing blood loss and improving clinical outcomes.

From the Departments of *Anesthesia and Pain Management, Laboratory Medicine, Clinical Biochemistry, and §the Toronto General Research Institute, Toronto General Hospital, University Health Network, University of Toronto, and Institute of Health Policy, Management, and Evaluation, University of Toronto, Toronto, Ontario, Canada.

Accepted for publication October 18, 2013.

Funding: Helena Laboratories (Beaumont, Texas) provided the material for PlateletWorks®. K. Karkouti is funded in part by a merit award from the Department of Anesthesia, University of Toronto.

The authors declare no conflicts of interest.

Reprints will not be available from the authors.

Address correspondence to Keyvan Karkouti, MSc, MD, FRCPC, Department of Anesthesia and Pain Management, Toronto General Hospital, University Health Network, 200 Elizabeth St., Toronto, Ontario, Canada, M5G 2C4. Address e-mail to keyvan.karkouti@uhn.ca.

© 2014 International Anesthesia Research Society