COVID and Coagulation

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The onset of COVID-19 presents many challenges to the medical community. Coagulation entered the fray with the discovery of abnormal clotting in patients with severe COVID-19.

Doctors originally thought COVID-19 was a respiratory virus, “albeit a contagious and lethal one with no vaccine or treatment.” However, cases that did not fit the pattern of a respiratory virus appeared to be increasing at an alarming rate. The doctors noticed 20-40% of COVID-19 patients had strange blood problems.  A clear pattern, based on age or chronic conditions, did not emerge and some scientists began to suspect severe changes in the patient’s blood caused some of the abnormalities. [1]

Patients were presenting with high D-Dimer levels, leading doctors to believe they were experiencing abnormal coagulation throughout the body. They reported patients with elevated D-Dimer levels over 1 mcg/L had much higher odds of death before discharge. [2]

Professor James O’Donnell, Director of Irish Centre for Vascular Biology, noted, “Our novel findings demonstrate that COVID-19 is associated with a unique type of blood clotting disorder that is primarily focused with the lungs and which undoubtedly contributes to the high levels of mortality being seen in patients with COVID-19.” They found in addition to pneumonia there were hundreds of small blood clots throughout the lungs.  Other lung infections do not include blood clots in the lungs, these blood clots explain the very low oxygen levels in severe COVID-19 patients.  Professor O’Donnell went on to say, “Understanding how these micro-clots are being formed within the lung is critical so that we can develop more effective treatments for our patients, particularly those in high risk groups.” [3]

Lewis Kaplan, a doctor at the University of Pennsylvania explained, “The problem we are having is that while we understand that there is a clot, we don’t yet understand why there is a clot.”  Harlan Krumholz, a cardiac specialist at the Yale New Haven Hospital Center hypothesized, “One of the theories is that once the body is so engaged in a fight against the invader, the body starts consuming the clotting factors, which can result in either blood clots or bleeding. In the Ebola virus, the balance was more toward bleeding.  In covid-19, it’s more blood clots.”(Cha, 2020) 

Recognizing that blood complications are a leading cause of death in COVID-19 patients is forcing many hospitals to rethink the management of the virus.  While respiratory distress is still the leading cause of death in COVID-19 patients, those dying from blood complications are not far behind.  Behood Bikdeli, a fellow from Columbia University Irving Medical Center, said “my guess is it’s one of the top three causes of demise and deterioration in COVID-19 patients.” Harlan Krumholz surmised, “There’s a lot of speculation. That’s one of the frustrating things about the virus.” Lewis Kaplan concurred, “We don’t know. And therefore, we are scared.”(Cha, 2020)

[1] Cha, A. (2020, April 22). A mysterious blood-clotting complication is killing coronavirus patients. Retrieved May 05, 2020, from

[2] Shaw, G. (2020, May 5). Abnormal Clotting and COVID-19. Retrieved from

[3] RCSI University of Medicine and Health Sciences. (2020, April 30). Blood clotting a significant cause of death in patients with COVID-19. ScienceDaily. Retrieved May 5, 2020 from