Intermediate dose heparin thromboprophylaxis among critically ill patients with COVID-19: a randomized clinical trial

BACKGROUND: The optimal thromboprophylaxis among critically ill adults with COVID-19 is uncertain. OBJECTIVES: To determine the effectiveness and safety of intermediate-dose heparin compared with standard low-dose thromboprophylaxis. METHODS: In an ongoing adaptive platform trial (randomized embedded multifactorial adaptive platform for community-acquired pneumonia), critically ill patients with COVID-19 were randomized to intermediate-dose heparin or standard low-dose thromboprophylaxis. Interventions were continued in hospital for up to 14 days. The primary endpoint was organ support-free days (OSFDs), an ordinal outcome combining in-hospital survival and the number of days free of intensive care unit-based respiratory or cardiovascular organ support through 21 days. The primary analysis was an adjusted Bayesian hierarchical cumulative logistic model. An odds ratio (OR) > 1.0 represents an improved outcome with intermediate-dose heparin. RESULTS: Between April 27, 2021 and November 25, 2023, 1255 critically ill adults with COVID-19 were enrolled from 78 sites in 15 countries, of whom 1254 completed follow-up (n = 572 intermediate-dose, n = 682 low-dose). Enrollment was terminated prior to reaching a prespecified statistical trigger due to declining case numbers and slow recruitment. Median age was 59 years, and 36.7% were female (n = 461/1255). The probability that intermediate-dose heparin improved OSFDs was 73.5% (OR, 1.06; 95% credible interval, 0.87, 1.30), which did not meet the prespecified superiority threshold of 99%. Hospital survival was 77.1% (441/572) and 76.7% (523/682) in the intermediate- and low-dose heparin groups, respectively (median adjusted OR, 1.14; 95% credible interval, 0.86, 1.52). Major bleeding occurred in 10 of 572 (1.7%) and 14 of 682 (2.1%) patients receiving intermediate and standard low doses, respectively. CONCLUSION: Intermediate-dose heparin did not improve OSFDs or survival compared with standard thromboprophylaxis in critically ill patients with COVID-19. (ClinicalTrials.gov number: CT02735707).