Thrombotic Complications in a Canadian Population of Critically Ill Patients with COVID-19
Authors: Camille Simard , Koolian Maral , Escobar Diana , Blostein Mark , Lipes Jed , Avram Adelina Teona , Kerzner Ryan , Mantzanis Helen , Porres Aguilar Mateo , Tagalakis Vicky 
Published: November 2020

Introduction
Coronavirus disease 2019 (COVID-19) is caused by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), a virus strain that appeared in Wuhan China in December 2019, that has since spread to become pandemic. An increased risk of venous and arterial thromboembolism has been consistently reported in critically ill patients with COVID-19 in several countries. The mechanism is thought to be multifactorial, largely mediated by the interplay between inflammation and the coagulation system, or thromboinflammation. We aim to report the risk of thrombosis in a Canadian patient population admitted to the intensive care unit (ICU) with COVID-19.
Method
We conducted a retrospective cohort study of all consecutive patients with COVID-19 admitted to the ICU between March 1st, 2020 and May 10th, 2020 at the Jewish General Hospital (JGH) in Montreal, Canada. The JGH is a tertiary care centre in Montreal, the epicenter of the COVID-19 pandemic in Canada, and the JGH was the first designated hospitalization centre in Montreal for COVID-19 patients. Patients were followed from date of ICU admission to the earliest of the following: objectively confirmed venous or arterial thrombosis; discharge from hospital; death; or study end date (May 24th, 2020). We determined risk of venous (pulmonary embolism (PE) and deep vein thrombosis (DVT)) and arterial (myocardial infarction, cerebrovascular accident, arterial limb ischemia, and mesenteric ischemia) thrombotic events.
Results
During the study period, a total of 90 patients admitted to the ICU with COVID-19 were included. The median age was 66 years (standard deviation (SD) 13.8), and 41.1% of patients were female. The median body mass index was 30 kg/m2(SD 5.1), and 64% of patients were mechanically ventilated and 10.1% received continuous renal replacement therapy. The median duration of follow-up was 17.1 days (SD 13.4). In all, 98.9% of patients were prescribed anticoagulation, among whom 78.2% were on a prophylaxis dose, 15.0% intermediate dose, and 6.9% therapeutic dose. In all, 11 (12.2%) patients developed a thrombotic complication among whom 9 patients had objectively diagnosed pulmonary embolism (PE) and 2 patients had an arterial thromboembolism. Both arterial events were cerebrovascular accidents. All PE episodes involved segmental arteries. One PE was incidental, and 3 patients had a concomitant diagnosis of DVT. Overall, death was observed in 16.7% of cohort patients and 12.2% of patients were still admitted to hospital at study end date.
Conclusion
In this first Canadian study of critically ill patients with COVID-19, we found a 12.2% risk of thrombotic complications despite almost 100% use of anticoagulation primarily with standard prophylaxis dosing. This risk is considerably lower than most reported estimates to date from critical care COVID-19 cohorts in Europe, China and the United States. Our results fuel the ongoing discussion of optimal dose of anticoagulation in these patients.

Disclosures
No relevant conflicts of interest to declare.