The Effects of Ultrafiltration on e-Aminocaproic Acid: An In Vitro Analysis

Abstract

Blood conservation strategies have become a standard of practice in cardiac surgery, with the use of antifibrinolytic agents and ultrafiltration two popular techniques. The purpose of this study was to evaluate the effects of continuous ultrafiltration on e-aminocaproic acid (EACA) utilizing functional coagulation analysis. A fibrinolytic assay was developed to detect EACA using the thromboelastograph (TEG) and urokinase (0.138 units 0.360 mL−1). Fresh bovine blood (23 ± 1% hematocrit) was pumped (100 mL min−1) through an ultrafiltrator (HPH 400) at 37°C with a transmembrane pressure of 280 mmHg. EACA (0.065 mg mL−1) was circulated for 10 minutes before initiating ultrafiltration. Samples (pre- and postultrafiltrator) were obtained at baseline, 5, and 10 min of ultrafiltration and analyzed via the fibrinolytic assay for EACA determination. TEG profiles significantly decreased from concentrations of 0.065 mg to 0.0325 mg of EACA mL−1 blood (maximum amplitude MA, 75.4 ± 4.0 versus 63.3 ± 2.9, p < .05, TEG index 5.4 ± 0.7 versus 4.0 ± 0.3, p < .05). Fibrinolysis at 30 min increased as EACA concentrations declined (0.065 mg, 0% versus 0.032 mg, 16.4 ± 2.8%, p < .05). During ultrafiltration the MA increased significantly from baseline to 10 min postultrafiltrator (68.2 ± 3.0 versus 75.8 ± 10.0, p < .05) and from 5 min pre- to 10 min postultrafiltrator (69.7 ± 4.2 versus 75.8 ± 10.0, p < .05). The TEG index showed no significant change, and no fibrinolysis was detected at 30 min from any datapoint during ultrafiltration. In conclusion, this study demonstrates that the antifibrinolytic properties of EACA are maintained during ultrafiltration with a 25% reduction in total circulating volume.