Coagulation Parameter Thresholds Associated with Non-Bleeding in the Eighth Hour of Adult Cardiac Surgical Post-Cardiotomy Extracorporeal Membrane Oxygenation

Abstract

Excessive bleeding and allogeneic transfusion during adult post-cardiotomy venoarterial extracorporeal membrane oxygenation (ECMO) are potentially harmful and expensive. Balancing the inhibition of clotting and distinguishing surgical from non-surgical bleeding in post-operative period is difficult. The sensitivity of coagulation tests including Thromboelastography(®) (TEG) to predict chest tube drainage in the early hours of ECMO was examined with the use of receiver-operating characteristics (ROC). The results are useful to incorporate in clinical evidence-based algorithms to guide management decisions. In the eighth hour of ECMO, 26 of the 53 adult patients (49%) studied were identified as non-bleeders (less than 2.0 mL/kg/h). All had experienced various types of cardiac surgical procedures. Fifty-two percent were female and the group was 54 ± 19 (mean ± 1 SD) years old. The coagulation parameter threshold with the maximum sensitivity and specificity to predict non-bleeding at 8 hours on ECMO was the kaolin plus heparinase TEG maximum amplitude (KH-TEG MA) at a significant ROC threshold (t) > 50 mm. The activated partial thromboplastin time (aPTT) t < 49 seconds, KH-TEG alpha-angle t > 51°, and the kaolin activated clotting time (ACT) t < 148 seconds were sensitive predictors of non-bleeders. The whole-blood KH-TEG MA was superior to the plasma-based aPTT or International Normalization Ratio (INR) to predict bleeding in the eighth hour of ECMO. Using coagulation laboratory thresholds that predict non-bleeding can begin a process of identifying patients earlier that are likely to bleed. Awareness of these parameter thresholds may improve care through patient protection from unnecessary transfusion and prolonging the life of the ECMO circuit. An algorithm incorporating the ROC thresholds was created to help recognize surgical bleeding to minimize unnecessary transfusions.

Keywords: Thromboelastography; anticoagulation; blood component transfusion; coagulation; extracorporeal life support; extracorporeal membrane oxygenation; hemorrhage; receiver operating characteristics.

Figures

Figure 1.

Box plots for the distribution of observed patient estimated blood loss by ECMO hour.

Figure 2.

ROC analysis for kaolin and heparinase-activated TEG MA with bleeding less than or greater than 2 mL/kg/h. ROC area = .77 and KH-TEG MA threshold = 50 mm (n = 53, p < .0001).

Figure 3.

The Bleeding Algorithm is to be used in the first 8 hours of post-cardiotomy ECMO to prepare for anticoagulant administration. AUC is ROC area under the curve for parameter threshold at bleeding less than 2.0 mL/kg/h. The Transfusion Algorithm is Figure 4.

Figure 4.

Algorithm to be used in the first 8 hours of post-cardiotomy ECMO to adjust coagulation monitoring parameters to minimize patient bleeding. AUC, ROC area under the curve for parameter threshold at bleeding less than 2.0 mL/kg/h; KTEG, kaolin-activated TEG; KHTEG, kaolin- and heparinase-activated TEG. Adapted from Nuttall GA, Oliver WC, Santrach PJ, et al. Anesthesiology. 2001;94;773–81.