Half-lives of albumin and cholinesterase in critically ill patients.

Background: Albumin and plasma cholinesterase are markedly reduced in critical illness. However, the plasma half-lives of these two proteins have only been determined in very limited numbers of patients mostly outside intensive care. Therefore, we determined the kinetics of decrease of albumin and cholinesterase in a large population of critically ill patients. Methods: Medical records of all patients of two university-affiliated surgical intensive care units during a time period of 8 years were retrospectively evaluated. To calculate the rate of fall, the first value in every episode of decreasing albumin or cholinesterase was arbitrarily set at 100% and the ensuing lower values were expressed as the respective fractions. Results: Records of 3591 patients were evaluated. Regression analysis exhibited an exponential evolution of albumin and cholinesterase over time with corresponding mean apparent plasma half-lives of 11.8 days [95% confidence interval (Cl): 10.8-12.9] for albumin and 7.8 days (95% Cl: 7.4-8.3) for cholinesterase. Conclusions: These findings suggest that the apparent plasma half-lives of albumin and cholinesterase in critically ill surgical patients are considerably shorter than previously determined.