Miranda Bowers, PharmD
University of Iowa Hospitals and Clinics
Disclosure information not submitted.
Ryan Hobbs
Clinical Pharmacy Specialist, Cardiology
University of Iowa Hospital and Clinics, United States
Disclosure information not submitted.
Lovkesh Arora, MD
ECMO Medical Director
Univ. of Iowa Hosp./ Clinics, Anes. Dept, United States
Disclosure information not submitted.
Title: Correlation of thromboelastography with heparin assay and PTT in ECMO anticoagulation management
INTRODUCTION: Systemic anticoagulation with unfractionated heparin is commonly used in extracorporeal membrane oxygenation (ECMO) to prevent blood clot development provoked by contact with the nonbiologic surfaces of the ECMO circuit. There are multiple strategies used for the monitoring of anticoagulation including partial thromboplastin time (PTT), heparin assay by anti-factor Xa, and thromboelastography (TEG). The initial phase of this study was a post-guideline change analysis comparing outcomes of heparin monitoring in ECMO patients via a PTT-based approach to TEG-based approach. We found that a TEG-based protocol was associated with a significantly longer period in the therapeutic range, significantly less systemic thrombosis, with no difference in bleeding. The purpose of the following correlation phase was to determine if there was utility in continuation of PTT or heparin assay lab draws in addition to TEG on our ECMO patients.
Methods: A single-center observational cohort study via retrospective chart review was performed for adult intensive care patients who received therapeutic heparin on VA- and VV-ECMO between October 2016 and October 2020. The correlation between TEG, PTT, and heparin assay values were assessed. Pearson correlation coefficients (r values) were utilized to assess correlations between TEG & PTT, and TEG & heparin assay. Data analysis was performed using SPSS Statistics Software.
Results: Eighty-two patients were included. Poor correlation was observed between TEG compared to PTT and heparin assays (r=0.204 and 0.268, respectively). Regardless of monitoring approach, when TEG was therapeutic, heparin assay was therapeutic 21.0% of the time with a median assay of 0.48 (0.42-0.53) U/mL, and PTT was therapeutic 28.1% of the time with a median of 52 (47-58) seconds.
Conclusions: Managing heparin with a TEG-based protocol appears to be a safe and feasible option for VA- and VV-ECMO patients. When using TEG to monitor heparin anticoagulation, it is reasonable to avoid checking PTT and heparin assays due to the poor correlation with TEG values.