The key COVID-19 findings in hematology, distilled into a clear, readable brief. The evidence is here whenever you want to go deeper.
INSIDE THIS MONITOR
35cited sources
14available findings
Study findings updated
AI-assisted evidence summary. For general information. These findings are not individual medical advice or a clinician endorsement.
THE SHORT VERSION
What’s worth knowing.
The key findings, what they mean, and the context that matters.
THE HEADLINE TAKEAWAY21%lower relative risk
Nebulized heparin lowered mortality in acute respiratory failure
Across randomized trials of adults with acute respiratory failure, nebulized heparin had a 21% lower relative risk of death from any cause than standard care or placebo.
Mortality was 17.1% with nebulized heparin and 22.1% with standard care or placebo. The major-bleeding analysis found no clear difference versus control; the supplied evidence does not specify the control regimen, and the estimate was imprecise.
See the evidence
21% lower relative risk, calculated from RR 0.79. This is not an absolute percentage-point difference.
All-cause mortality reduction with nebulized heparin in respiratory failure
RR 0.79 95% CI: 0.66-0.95
Fresilli, Stefano et al.. Nebulized Heparin in Adults With Acute Respiratory Failure: A Meta-Analysis of Randomized Trials.. Critical care medicine. 2026.
Fresilli, Stefano et al.. Nebulized Heparin in Adults With Acute Respiratory Failure: A Meta-Analysis of Randomized Trials.. Critical care medicine. 2026.
Fresilli, Stefano et al.. Nebulized Heparin in Adults With Acute Respiratory Failure: A Meta-Analysis of Randomized Trials.. Critical care medicine. 2026.
Major bleeding with nebulized heparin vs control (non-significant)
RR 1.48 95% CI: 0.42-5.18
Fresilli, Stefano et al.. Nebulized Heparin in Adults With Acute Respiratory Failure: A Meta-Analysis of Randomized Trials.. Critical care medicine. 2026.
Intermediate-dose heparin did not clearly improve organ-support-free days
No clear difference
In critically ill patients with COVID-19, intermediate-dose heparin did not clearly improve organ-support-free days compared with standard low-dose heparin.
This randomized trial reported hospital survival of 77.1% with intermediate-dose and 76.7% with standard low-dose heparin; major bleeding was 1.7% and 2.1%, respectively. The organ-support timeframe is not available in this summary, and equal efficacy was not established.
See the evidence
The reported result does not establish a difference; it does not prove equivalence.
Organ support-free days with intermediate-dose heparin vs. standard low-dose
OR 1.06 95% credible interval: 0.87, 1.30
Bradbury, Charlotte A et al.. Intermediate dose heparin thromboprophylaxis among critically ill patients with COVID-19: a randomized clinical trial.. Journal of thrombosis and haemostasis : JTH. 2026.
Bradbury, Charlotte A et al.. Intermediate dose heparin thromboprophylaxis among critically ill patients with COVID-19: a randomized clinical trial.. Journal of thrombosis and haemostasis : JTH. 2026.
Bradbury, Charlotte A et al.. Intermediate dose heparin thromboprophylaxis among critically ill patients with COVID-19: a randomized clinical trial.. Journal of thrombosis and haemostasis : JTH. 2026.
Bradbury, Charlotte A et al.. Intermediate dose heparin thromboprophylaxis among critically ill patients with COVID-19: a randomized clinical trial.. Journal of thrombosis and haemostasis : JTH. 2026.
Bradbury, Charlotte A et al.. Intermediate dose heparin thromboprophylaxis among critically ill patients with COVID-19: a randomized clinical trial.. Journal of thrombosis and haemostasis : JTH. 2026.
Venous clots were frequent in COVID-19 intensive care
27.9%
Blood clots in veins occurred in 27.9% of intensive care patients with COVID-19 despite preventive anticoagulation.
This systematic review and meta-analysis pooled thromboembolism incidence in intensive care. It does not compare different prophylaxis strategies, and the observation period is not available in this summary.
See the evidence
VTE incidence in COVID-19 ICU patients
27.9%
Malas MB, Naazie IN, Elsayed N, et al. Thromboembolism risk of COVID-19 is high and associated with a higher risk of mortality: A systematic review and meta-analysis. EClinicalMedicine. 2020;29-30:100639.
Study-specific findings. Different populations, treatments and follow-up periods can produce different results.
THE RESEARCH, AS IT ARRIVES
Latest studies.
The newest findings added to this collection. The learning from each, already distilled.
Study summaries are not available in this collection yet. The original evidence remains accessible in each monitor.
Dates show when findings were added here, not when papers were published. Study populations and comparisons differ.
WHEN YOU WANT TO GO DEEPERSee all 14 findingsOriginal results, comparisons and study details.
5 of 5 source groupsFindings stay together with their study.
SOURCE 111 finding
Zhou F, Yu T, Du R, et al. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. Lancet. 2020;395(10229):1054-1062.
Tang N, Li D, Wang X, Sun Z. Abnormal coagulation parameters are associated with poor prognosis in patients with novel coronavirus pneumonia. J Thromb Haemost. 2020;18(4):844-847.
Fresilli, Stefano et al.. Nebulized Heparin in Adults With Acute Respiratory Failure: A Meta-Analysis of Randomized Trials.. Critical care medicine. 2026.
Bradbury, Charlotte A et al.. Intermediate dose heparin thromboprophylaxis among critically ill patients with COVID-19: a randomized clinical trial.. Journal of thrombosis and haemostasis : JTH. 2026.
Browse the 35 original sourcesThe complete bibliography behind this monitor.
[1]
Malas MB, Naazie IN, Elsayed N, et al. Thromboembolism risk of COVID-19 is high and associated with a higher risk of mortality: A systematic review and meta-analysis. EClinicalMedicine. 2020;29-30:100639.
Nopp S, Moik F, Jilma B, et al. Risk of venous thromboembolism in patients with COVID-19: A systematic review and meta-analysis. Res Pract Thromb Haemost. 2020;4(7):1178-1191.
Jimenez D, Garcia-Sanchez A, Rali P, et al. Incidence of VTE and Bleeding Among Hospitalized Patients With Coronavirus Disease 2019: A Systematic Review and Meta-analysis. Chest. 2021;159(3):1182-1196.
Suh YJ, Hong H, Ohana M, et al. Pulmonary Embolism and Deep Vein Thrombosis in COVID-19: A Systematic Review and Meta-Analysis. Radiology. 2021;298(2):E70-E80.
REMAP-CAP, ACTIV-4a, ATTACC Investigators. Therapeutic Anticoagulation with Heparin in Critically Ill Patients with Covid-19. N Engl J Med. 2021;385(9):777-789.
REMAP-CAP, ACTIV-4a, ATTACC Investigators. Therapeutic Anticoagulation with Heparin in Noncritically Ill Patients with Covid-19. N Engl J Med. 2021;385(9):790-802.
INSPIRATION Investigators. Effect of Intermediate-Dose vs Standard-Dose Prophylactic Anticoagulation on Thrombotic Events, Extracorporeal Membrane Oxygenation Treatment, or Mortality Among Patients With COVID-19 Admitted to the Intensive Care Unit: The INSPIRATION Randomized Clinical Trial. JAMA. 2021;325(16):1620-1630.
Spyropoulos AC, Goldin M, Giannis D, et al. Efficacy and Safety of Therapeutic-Dose Heparin vs Standard Prophylactic or Intermediate-Dose Heparins for Thromboprophylaxis in High-risk Hospitalized Patients With COVID-19: The HEP-COVID Randomized Clinical Trial. JAMA Intern Med. 2021;181(12):1612-1620.
Sholzberg M, Tang GH, Rahhal H, et al. Effectiveness of therapeutic heparin versus prophylactic heparin on death, mechanical ventilation, or intensive care unit admission in moderately ill patients with covid-19 admitted to hospital: RAPID randomised clinical trial. BMJ. 2021;375:n2400.
Ramacciotti E, Agati LB, Calderaro D, et al. Rivaroxaban versus no anticoagulation for post-discharge thromboprophylaxis after hospitalisation for COVID-19 (MICHELLE): an open-label, multicentre, randomised, controlled trial. Lancet. 2022;399(10319):50-59.
Zhou F, Yu T, Du R, et al. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. Lancet. 2020;395(10229):1054-1062.
Tang N, Li D, Wang X, Sun Z. Abnormal coagulation parameters are associated with poor prognosis in patients with novel coronavirus pneumonia. J Thromb Haemost. 2020;18(4):844-847.
Bilaloglu S, Aphinyanaphongs Y, Jones S, et al. Thrombosis in Hospitalized Patients With COVID-19 in a New York City Health System. JAMA. 2020;324(8):799-801.
Ackermann M, Verleden SE, Kuehnel M, et al. Pulmonary Vascular Endothelialitis, Thrombosis, and Angiogenesis in Covid-19. N Engl J Med. 2020;383(2):120-128.
Goshua G, Pine AB, Meizlish ML, et al. Endotheliopathy in COVID-19-associated coagulopathy: evidence from a single-centre, cross-sectional study. Lancet Haematol. 2020;7(8):e575-e582.
Pretorius E, Vlok M, Venter C, et al. Persistent clotting protein pathology in Long COVID/Post-Acute Sequelae of COVID-19 (PASC) is accompanied by increased levels of antiplasmin. Cardiovasc Diabetol. 2021;20(1):172.
Grobbelaar LM, Venter C, Vlok M, et al. SARS-CoV-2 spike protein S1 induces fibrin(ogen) resistant to fibrinolysis: implications for microclot formation in COVID-19. Biosci Rep. 2021;41(8):BSR20210611.
Townsend L, Fogarty H, Dyer A, et al. Prolonged elevation of D-dimer levels in convalescent COVID-19 patients is independent of the acute phase response. J Thromb Haemost. 2021;19(4):1064-1070.
Cuker A, Tseng EK, Nieuwlaat R, et al. American Society of Hematology 2021 guidelines on the use of anticoagulation for thromboprophylaxis in patients with COVID-19. Blood Adv. 2021;5(3):872-888.
Moores LK, Tritschler T, Brosnahan S, et al. Prevention, Diagnosis, and Treatment of VTE in Patients With Coronavirus Disease 2019: CHEST Guideline and Expert Panel Report. Chest. 2020;158(3):1143-1163.
Spyropoulos AC, Levy JH, Ageno W, et al. Scientific and Standardization Committee communication: Clinical guidance on the diagnosis, prevention, and treatment of venous thromboembolism in hospitalized patients with COVID-19. J Thromb Haemost. 2020;18(8):1859-1865.
See I, Su JR, Lale A, et al. US Case Reports of Cerebral Venous Sinus Thrombosis With Thrombocytopenia After Ad26.COV2.S Vaccination, March 2 to April 21, 2021. JAMA. 2021;325(24):2448-2456.
Fresilli, Stefano et al.. Nebulized Heparin in Adults With Acute Respiratory Failure: A Meta-Analysis of Randomized Trials.. Critical care medicine. 2026.
Bradbury, Charlotte A et al.. Intermediate dose heparin thromboprophylaxis among critically ill patients with COVID-19: a randomized clinical trial.. Journal of thrombosis and haemostasis : JTH. 2026.
This is an AI-assisted evidence summary, not a clinician endorsement. Read each original paper for its complete methods, population and limitations. Different studies can ask different questions and report different kinds of results.
Dates marked “added” describe when a finding entered this monitor, not when the study was published or clinically reviewed. Personal health and treatment decisions belong in a conversation with a qualified clinician.