Impact of C-Reactive Protein on Anticoagulation Monitoring in Extracorporeal Membrane Oxygenation

Objective To evaluate the impact of inflammation on anticoagulation monitoring for patients supported with extracorporeal membrane oxygenation (ECMO) Design Prospective single-center cohort study Setting University-affiliated tertiary care academic medical center Participants Adult venovenous and venoarterial ECMO patients anticoagulated with heparin Measurements and Main Results C-Reactive protein (CRP) was used as a surrogate for overall inflammation. The relationship between CRP and the partial thromboplastin time (PTT, seconds) was evaluated using a CRP-insensitive PTT assay (PTT-CRP) in addition to measurement using routine PTT assay. Data from 30 patients anticoagulated with heparin over 371 ECMO days was included. CRP levels (mg/dL) were significantly elevated (median 17.2, IQR, 9.2-26.1) and 93% of patients had a CRP ≥ 5. The median PTT (58.9 (46.9-73.3)) was prolonged by 11.3 seconds compared to simultaneously measured PTT-CRP (47.6 (40.1-55.5), p<0.001). The difference between PTT and PTT-CRP generally increased with CRP elevation from 2.7 for CRP < 5.0 to 13.0 for CRP between 5-10, 17.7 for CRP between 10-15, and 15.1 for CRP > 15 (p<0.001). In a subgroup of patients, heparin was transitioned to argatroban, and a similar effect was observed (PTT: 62.1 (53.0-78.5) vs. PTT-CRP: 47.6 (41.3-57.7), p<0.001). Conclusions Elevations in CRP are common during ECMO and can falsely prolong PTT measured by commonly used assays. The discrepancy due to CRP-interference is clinically important given narrow PTT targets and may contribute to hematologic complications. To evaluate the impact of inflammation on anticoagulation monitoring for patients supported with extracorporeal membrane oxygenation (ECMO) Prospective single-center cohort study University-affiliated tertiary care academic medical center Adult venovenous and venoarterial ECMO patients anticoagulated with heparin C-Reactive protein (CRP) was used as a surrogate for overall inflammation. The relationship between CRP and the partial thromboplastin time (PTT, seconds) was evaluated using a CRP-insensitive PTT assay (PTT-CRP) in addition to measurement using routine PTT assay. Data from 30 patients anticoagulated with heparin over 371 ECMO days was included. CRP levels (mg/dL) were significantly elevated (median 17.2, IQR, 9.2-26.1) and 93% of patients had a CRP ≥ 5. The median PTT (58.9 (46.9-73.3)) was prolonged by 11.3 seconds compared to simultaneously measured PTT-CRP (47.6 (40.1-55.5), p<0.001). The difference between PTT and PTT-CRP generally increased with CRP elevation from 2.7 for CRP < 5.0 to 13.0 for CRP between 5-10, 17.7 for CRP between 10-15, and 15.1 for CRP > 15 (p<0.001). In a subgroup of patients, heparin was transitioned to argatroban, and a similar effect was observed (PTT: 62.1 (53.0-78.5) vs. PTT-CRP: 47.6 (41.3-57.7), p<0.001). Elevations in CRP are common during ECMO and can falsely prolong PTT measured by commonly used assays. The discrepancy due to CRP-interference is clinically important given narrow PTT targets and may contribute to hematologic complications.