Perturbations in laboratory values after coronary artery bypass graft surgery with cardiopulmonary bypass.

Objective: The purpose of this study was to describe the sequential changes in commonly obtained laboratory values after coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB).

Methods: The authors examined laboratory data from 375 patients who underwent uncomplicated CABG with CPB in a multicenter clinical trial of a medication for postoperative pain. Data were obtained preoperatively, at the time of postoperative extubation, and at 4 subsequent intervals ending 14 days after extubation. Data obtained before study drug administration are reported for all patients; thereafter, only data from placebo patients without perioperative complications (n=123) are reported.

Results: Mean postoperative coagulation values remained within their reference ranges at the time of extubation. However, platelet counts increased to a peak value well above the reference range by the end of the study. Postoperative white blood cell counts rose above the reference range, mainly because of increased neutrophils. Serum chemistries were also altered; most patients showed a persistent postoperative hyperglycemia. Creatine kinase levels rose to nearly 4 times the upper limit of the reference range in the early postoperative period. Lactate dehydrogenase, serum aspartate aminotransferase, and alanine aminotransferase levels also increased above the reference range. Total protein and albumin values were below the reference range throughout the postoperative period.

Conclusions: Laboratory values for hematology, blood coagulation, and serum chemistry change substantially after uncomplicated CABG with CPB. Recognition of these changes will facilitate the conduct of clinical research and may prevent inappropriate treatment based on abnormal laboratory findings that have no clinical significance.