NASA Develops VTE Risk Score Algorithm to Safeguard Astronauts from Blood Clots
NASA creates a VTE risk score for astronauts, using ultrasound data and terrestrial research to guide clot‑prevention in microgravity.
In April 2026 NASA’s Office of the Chief Health and Medical Officer convened a working group to confront a growing concern: venous thromboembolism (VTE) among crew members in microgravity. Recent ISS missions have revealed altered blood flow, especially stasis in the left internal jugular vein, that could predispose astronauts to dangerous clots. By translating terrestrial research into a space‑specific risk‑assessment tool, NASA aims to standardize prophylaxis decisions and protect crew health on long‑duration flights. The new VTE Risk Score algorithm marks the first evidence‑based framework for anticoagulation use in orbit.
What happened
The working group, formed in April 2026, reviewed updated VTE case data, in‑flight ultrasound findings, and recent literature on thrombosis risk factors. They identified left internal jugular vein stasis as a dominant microgravity risk, while also noting uncertainties around slow qualitative flow, endothelial changes, and retrograde flow.
Building on that review, the panel crafted a weighted algorithm that assigns points for stasis, retrograde flow, and additional terrestrial risk factors such as prior clot history, hormonal therapy, and immobilization. The score triggers anticoagulation prophylaxis when stasis alone reaches a threshold, or when a combination of lower‑weight factors accumulates to the same level.
Why it matters
Clot formation in space can jeopardize mission success, crew safety, and the feasibility of future deep‑space travel. A transparent scoring system helps medical officers make timely, consistent decisions, reducing both under‑ and over‑treatment. It also guides future research by highlighting data gaps, such as real‑time flow measurement capabilities.
- Standardizes prophylaxis decisions across missions.
- Integrates both space‑specific and terrestrial risk data.
- Provides a clear trigger for medical intervention.
- Relies on ultrasound assessments that are limited in microgravity.
- Anticoagulation carries bleeding risk, especially in a confined habitat.
- Algorithm may need recalibration as new flight data emerge.
How to think about it
Treat the VTE Risk Score as a decision‑support tool rather than a definitive rule. First, obtain the best possible ultrasound measurement of jugular flow; if stasis is confirmed, apply the score immediately. Second, tally any additional risk factors—previous VTE, hormonal therapy, prolonged immobilization—and add their points. If the total meets the prophylaxis threshold, initiate low‑dose anticoagulation under medical supervision, while monitoring for signs of bleeding. Re‑evaluate the score regularly, especially after major mission events such as EVA or crew‑rotation.
FAQ
What is the primary trigger for anticoagulation in the new algorithm?+
Can the score be used on short‑duration missions?+
How does NASA plan to improve in‑flight ultrasound measurements?+
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