Agitated saline (“bubble”) studies are simple, safe, and wildly informative. In a few heartbeats, you can unmask right-to-left shunts, clarify cryptogenic stroke workups, and troubleshoot unexplained hypoxemia. Here’s a clean, repeatable approach you can rely on.

When to do a bubble study

• Suspected intracardiac shunt: PFO/ASD in cryptogenic stroke, migraine with aura, decompression illness.
• Suspected intrapulmonary shunt: Pulmonary AVMs, hepatopulmonary syndrome.
• Unexplained hypoxemia or platypnea–orthodeoxia.
• Anomalous venous return clues: e.g., persistent left SVC (with left arm injection opacifying the coronary sinus first).

Communicating safety to nursing staff

(“chill—it’s just bubbles”)

Depending on your facility, injection may be in your scope of practice, but for those that still require nursing staff to inject, there can be some misunderstanding when you ask a nurse to inject air bubbles into your patient's arm. So here are some tips on how to communicate with nurses who might be unsure:

• What it is: Sterile normal saline agitated with a tiny volume of room air (≈0.5–1 mL) through a 3-way stopcock to create microbubbles. Unlike free air, these microbubbles are transient and dissolve within seconds—this is not an IV air embolism.
• Why it’s generally safe: No drug, no iodine—just saline + microbubbles that are trapped/filtered by the lungs and rapidly reabsorb. Used worldwide for decades with an excellent safety record when prepared and injected correctly.
• Standard mix & push: 9 mL saline + 1 mL air (optional 0.5 mL blood for stability), agitate 10–20 times between syringes, brisk injection on cue, then a 5–10 mL saline flush. Keep all Luer connections snug; the only air in the system is the measured 0.5–1 mL used to make bubbles.
• IV & monitoring: 18–22 g peripheral IV preferred; continuous ECG and pulse ox; supine or semi-recumbent. Expect brief RA opacification and possible transient cough/pressure sensation. Stop if the patient reports chest pain, dizziness, or any neuro change.
• Quick script you can use: “We’re going to inject agitated saline—sterile salt water with a tiny bit of air turned into microbubbles. They’re too small to cause harm and clear in seconds. On my cue, push quickly and then flush. If the patient coughs or feels off, we pause.”
• Contraindications: “Who shouldn’t get it?” Use clinical judgment and local policy. Be cautious in severe decompensated pulmonary hypertension, hemodynamic instability, or if you cannot ensure secure IV access. Never inject into an arterial line.

Set-up & recipe

Equipment

• 2 syringes (10 mL), 3-way stopcock, peripheral IV (18–22 g), normal saline, a touch of room air.

Mix

• Draw 9 mL saline + 1 mL air (optionally 0.5 mL patient blood for more stable bubbles).
• Rapidly agitate between syringes 10–20 times to create a dense microbubble suspension.
• Keep the stopcock taps snug (no stray air), and inject briskly.

Pro tip: Use right antecubital for standard PFO/ASD screening. Use left arm if you want to test for left SVC (watch for coronary sinus lighting up first). Use femoral if you’re sorting intracardiac vs intrapulmonary shunt timing.

Imaging views & timing

• Primary: Apical 4-chamber (A4C) focused on the interatrial septum.
• Helpful: Subcostal 4-chamber, parasternal short axis at the aortic level (IAS en face), and a focused IAS zoom.
• Run continuous clips from pre-injection through at least 10 cardiac cycles after RA opacification.
• If Valsalva/cough is used, coach and practice once, then inject during strain and release on cue.

The timing rule (your on-scan cheat sheet)

• RA opacifies immediately after injection (that’s your time zero).
• Bubbles in LA/LV ≤ 3 beats → intracardiac shunt (most often PFO/ASD).
• Bubbles in LA/LV after 3–8 beats → intrapulmonary shunt (e.g., PAVM).
• No bubbles across → negative study (re-try with a stronger Valsalva if suspicion remains).

Pro Tip: If you see coronary sinus opacify first with a left-arm injection, think persistent left SVC—document the sequence.

Getting the Valsalva right

• Aim to raise RA pressure: have the patient strain against a closed glottis (pretend to blow through a blocked straw) for ~5–8 seconds.
• Inject during strain, watch RA fill, then release (that pressure gradient promotes transient right-to-left flow).
• If Valsalva is tough, a sharp cough at RA opacification can substitute.

What to record (so good it charts)

• Injection site (right arm, left arm, femoral) and number of passes.
• Whether Valsalva/cough was used and adequacy.
• Beat count to first LA/LV bubbles.
• Qualitative shunt grade (e.g., sparse/moderate/dense—some labs use counts per frame).
• Any coronary sinus first finding (left SVC clue).

Pearls & pitfalls

Pearls

• Poor bubbles? Add a tiny drop of blood or agitate more vigorously.
• Zoom on IAS to catch subtle crossover.
• Consider a second site (femoral) if timing is equivocal.

Pitfalls

• Under-agitated saline = false negative.
• Weak Valsalva = missed PFO.
• Gain too high = shimmering artifact that mimics microbubbles.
• Mistaking late (pulmonary) appearance for PFO—count the beats.

Safety snapshot

• Agitated saline is generally well tolerated; microbubbles dissolve quickly in the pulmonary bed.
• Use standard IV safety checks; avoid paradoxical air entry from loose stopcocks or line issues.
• For definitive anatomic detail (size, tunnel, aneurysmal septum), consider TEE if clinically indicated.

Sample report language

Agitated saline contrast via right antecubital vein. Dense RA opacification achieved. With Valsalva release, microbubbles appeared in the LA within 2 cardiac cycles, consistent with a right-to-left intracardiac shunt (probable PFO). Shunt graded moderate. Coronary sinus did not opacify first. Findings support consideration of further evaluation per clinical context.

When to escalate

• Persistently negative but high clinical suspicion → repeat with verified Valsalva, alternate venous site, or TEE.
• Suspected pulmonary AVM → needs targeted imaging (contrast CT) after a positive delayed-appearance study.

Bottom line: Master the mix, the timing, and the beat count. Do that, and your saline studies will be So Good It Hertz—clear, consistent, and clinically decisive.

And just for fun - check out some of our "Chill It's Just Bubbles" merch!

-Lara Williams, BS, ACS, RCCS, RDCS, RVT, RDMS, FASE

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