Platelet dysfunction as measured by a point-of-care monitor is an independent predictor of high blood loss in cardiac surgery.
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 × 10/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.
David
D
Orlov
Stuart A
SA
McCluskey
Rita
R
Selby
Paul
P
Yip
Jacob
J
Pendergrast
Keyvan
K
Karkouti
D000368:Aged; D000465:Algorithms; D001780:Blood Coagulation Tests; D016063:Blood Loss, Surgical; D001792:Blood Platelets / Q000166:cytology*; D006348:Cardiac Surgical Procedures / Q000009:adverse effects* / Q000379:methods; D002315:Cardiopulmonary Bypass / Q000009:adverse effects* / Q000379:methods; D003094:Collagen / Q000378:metabolism; D004912:Erythrocytes / Q000166:cytology; D005260:Female; D006470:Hemorrhage; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010976:Platelet Count; D019095:Point-of-Care Systems; D016012:Poisson Distribution; D019106:Postoperative Hemorrhage / Q000209:etiology; D011446:Prospective Studies; D015203:Reproducibility of Results
D003094:Collagen