Case File: Fainting the Night After Landing

What is the most likely explanation, and why does it happen?

Postflight orthostatic intolerance. In weightlessness, fluid shifts toward the head and the body responds by reducing plasma volume by about 15% within about 2 days. Heart muscle mass and baroreflex sensitivity also decline. Back in gravity, blood pools in the legs, and the smaller blood volume cannot keep blood pressure up on standing [1].

It is worse after long missions. In 10-minute tilt tests on landing day, only 2 of 6 International Space Station (ISS) astronauts finished the test, compared with 52 of 65 Space Shuttle astronauts [2]. NASA’s brief notes that women appear more susceptible [1].

What else must you rule out before calling it “just readaptation”?

• Arrhythmia: get an ECG and monitor (done here: normal).
• Bleeding or anemia: red cell mass is about 10–12% lower after flight [3], so a mild drop is expected, but a large drop is not.
• Dehydration from motion-sickness vomiting, infection, or heat.
• Venous thrombosis and pulmonary embolism: in a study of 11 ISS crewmembers, 6 had stagnant or reversed flow in the internal jugular vein during flight, and one had a blocking clot [4]. Ask about neck and leg swelling, chest pain and low oxygen.
• Head injury from the fall.

Readaptation is common, but it does not protect anyone from stroke, heart attack or pulmonary embolism. See the clinician quick-start.

How do you treat her?

Treat it as low-volume orthostatic hypotension:

• Lie her down; raise her in stages (lie, then sit, then stand), with help.
• Fluids: oral if she can keep them down, otherwise intravenous isotonic saline. NASA landing kits carry at least 3 L of saline per crewmember [3].
• Lower-body compression. In 11 astronauts after about 6 months in flight, a gradient compression garment worn on landing day kept the heart rate and blood pressure response to standing at preflight levels [5].
• Keep her cool, and treat nausea [1].
• Drugs such as midodrine have limited supporting data and are not routine [1].

What is the expected course, and what advice do you give at discharge?

• Most crew recover tilt tolerance within days: 3 days after landing, 13 of 15 ISS astronauts completed the tilt test [2].
• No driving. NASA crew are usually advised not to drive during the first week [3].
• Most astronauts return to normal activities within about 45 days [3].
• Falls precautions at home: sit before standing, night light, someone nearby.
• Return if fainting recurs with injury, chest pain or palpitations, or symptoms are still significant after the first week.