Correspondence  |   August 2016
In Reply
Author Notes
  • Yale School of Medicine, New Haven, Connecticut (M.L.F.).
  • (Accepted for publication April 28, 2016.)
    (Accepted for publication April 28, 2016.)×
Article Information
Correspondence   |   August 2016
In Reply
Anesthesiology 8 2016, Vol.125, 438-439. doi:10.1097/ALN.0000000000001190
Anesthesiology 8 2016, Vol.125, 438-439. doi:10.1097/ALN.0000000000001190
We appreciate comments from Drs. Hui and Yu regarding our published article titled “Platelet Counts, Acute Kidney Injury, and Mortality after Coronary Artery Bypass Grafting Surgery.”1  The letter indicated that “despite the elaborate statistical analysis and the innovative perspectives,” they were concerned over “the study design and the interpretation of statistical results” of our study. More specifically, the letter highlighted that information on perioperative blood loss was not included in the logistic regression analysis and “suggest focusing more attention on perioperative blood loss, rather than platelets reduction in future research studies on postoperative acute kidney injury.” In support of their statement, Drs. Hui and Yu critiqued that significant blood loss is an independent risk factor for postoperative acute kidney injury (AKI) and in-hospital mortality after cardiac surgery. However, all studies cited in support of their statement did not directly test blood loss as a predictor of AKI. For example, one study defined significant blood loss as a need for large volume of blood transfusion (administration of more than or equal to 5 units of packed erythrocytes within 1 day of surgery)2 ; another reviewed risk factors and management of AKI without discussing the role of blood loss for predicting perioperative AKI3 ; another study was conducted in patients undergoing noncardiac surgery and investigated the role of perioperative hemoglobin as a predictor of AKI4 ; and the last citation was a meta-analysis of studies about the effects of perioperative hemodynamic optimization for postoperative renal dysfunction.5  Although several studies have found transfusion and anemia to be associated with AKI in cardiac surgery, none have addressed blood loss itself as a predictor.6–8  Further, the incidence of major bleeding requiring reoperation after elective coronary artery bypass grafting surgery is reported to be around 2.1%,9  and therefore given this low incidence, it is unlikely that major bleeding and/or blood loss accounted for a higher risk for AKI in our study. In addition, accurate measurement of blood loss intraoperatively in cardiac surgery with the use of cardiopulmonary bypass has limitations. Similarly, chest tube outputs after surgery is not a reliable method of capturing blood loss because the hemoglobin content in the chest tube is not measured.
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