Thromboelastography Identifies Undetected Blood Clots in COVID-19 Patients

The coronavirus disease 2019 (COVID-19) pandemic has caused more than 400,000 deaths globally. Disseminated intravascular coagulopathy and other COVID-19–associated coagulopathies occur among patients with severe SARS-CoV-2 infections.

Thromboelastography (TEG) is a method of testing the efficiency of blood coagulation. It is a test mainly used in surgery and anesthesiology, although increasingly used in resuscitations in Emergency Departments, intensive care units, and labor and delivery suites.

Intensive Care Physicians at the Baylor St Luke’s Medical Center (Houston, TX, USA) and their associates observed 21 patients with COVID-19 infection from March 15 to April 9, 2020, confirmed with reverse transcription–polymerase chain reaction test of nasopharyngeal swab. All patients underwent TEG and TEG with heparinase correction on ICU admission. Hypercoagulability was defined as elevated fibrinogen activity greater than a 73° angle or maximum amplitude (MA) more than 65 mm on TEG with heparinase correction.

The doctors found that the standard clotting profile or screening of the patients was fairly normal. They were then moved to the next level of more specific clotting tests, which included analyzing a patient's fibrinogen and D dimer levels. Fibrinogen is the protein that makes up the clot and D dimer levels are used to indicate the rate at which a patient's clots are being broken down, which would usually suggest that the body is "chewing up" all of the clotting factors. For the COVID-19 patients in the ICU, the team found that the levels of fibrinogen were more than three times the normal range, indicating that the body was churning out this protein. Looking at these two results together, there was no clear indication that these patients were at increased risk for forming blood clots.

When the investigators used the thromboelastography test, they discovered the patients who they found were clotting their central intravenous and arterial lines and dialysis catheters had abnormally high clotting function compared to the patients who did not have clotting issues, and the clot breakdown function was significantly higher in the patients who were clotting less than others. Among the 21 patients studied, 13 of them, or 62%, developed 46 blood clots that could only be detected through the TEG test. For patients who are at a higher risk of blood clots as indicated by the TEG test, the team recommended administering additional blood thinners.

Todd K. Rosengart, MD, a cardiothoracic surgeon and senior author of the study, said, “The TEG test should be performed on all COVID-19 ICU patients immediately to find those who are at a higher risk of clotting. At the point where physicians discover that their central line and catheter is clotting, the horse is out of the barn.” The study was published on June 5, 2020 in the journal JAMA Network Open.

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