American Society of Hematology living guidelines on the use of anticoagulation for thromboprophylaxis in patients with COVID-19: May 2021 update on the use of intermediate intensity anticoagulation in critically ill patients.

Abstract Background: COVID-19 related critical illness is associated with an increased risk of venous thromboembolism (VTE). Objective:These evidence-based guidelinesof the American Society of Hematology (ASH) are intended to support patients, clinicians and other health care professionalsin decisions aboutthe use of anticoagulation for thromboprophylaxis in patients with COVID-19-related critical illness who do not have confirmed or suspected VTE. Methods:ASH formed a multidisciplinary guideline panel, including three patient representatives,and applied strategies to minimize potential bias from conflicts of interest. The McMaster University GRADE Centre supported the guideline development process, including performing systematic evidence reviews(up to March 5, 2021).The panel prioritized clinical questionsand outcomes according to their importance for clinicians and patients. The panel used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approachto assess evidence and make recommendations, which were subject to public comment. This is an update on guidelines published in February 2021. Results:The panel agreed on one additional recommendation. The panel issued a conditional recommendation in favor of prophylactic-intensity over intermediate-intensity anticoagulation in patients with COVID-19 related-critical illness who do not have confirmed or suspected VTE. Conclusions: This recommendation was based on low certainty in the evidence, underscoring the need for further high-quality, randomized controlled trials comparing different intensities of anticoagulation in critically ill patients. Other key research priorities include better evidence on predictors of thrombosis and bleeding risk in critically ill patients with COVID-19 and the impact of non-anticoagulant therapies (e.g., antiviral agents, corticosteroids) on thrombotic risk.