Presyncope During a Venous Duplex in a Pregnant Patient on Anticoagulation
A 34-year-old woman is scheduled for a 45-minute bilateral lower extremity venous duplex for new left leg swelling that began 2 days ago after a 9-hour flight. She is 34 weeks pregnant, has fainted twice during blood draws, and has been taking low-molecular-weight heparin since yesterday evening, started in the emergency department. Her left calf is 3 cm larger than the right and tender. She has no chest pain or breathlessness. Ten minutes into the supine examination she becomes pale and diaphoretic, her heart rate falls from 84 to 52 bpm, and she reports nausea and that 'everything is going grey.' The referring team has asked for a complete study including compression of the common femoral and popliteal veins on both sides, and the waiting room is full.
1. What are your actions in the first two minutes?
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Stop the examination immediately and stay with the patient. Lay her supine with the head flat and the legs elevated (or use left lateral uterine displacement with a wedge if she is near term), loosen any tight clothing, apply a cool cloth, and recheck pulse, blood pressure, and oxygen saturation. Bradycardia with pallor and diaphoresis after a known needle-related fainting history is most consistent with a vasovagal response, but she is 34 weeks pregnant with a possible DVT, so you must also actively look for pulmonary embolism: ask about chest pain and breathlessness, check respiratory rate and saturation, and note whether she recovers promptly when supine. If she does not improve within a minute or two, or develops chest pain, hypoxia, or persistent tachycardia, call for emergency help. Document the vitals, the event timing, and the interventions.
2. How do you balance the need to compress a possible iliofemoral DVT against her anticoagulation and pregnancy?
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Compression is the diagnostic core of the examination and should not be abandoned, because a limited study that leaves the femoral and popliteal veins unexamined is not clinically useful in a patient with a 3 cm calf difference. Anticoagulation reduces, but does not eliminate, the risk of thrombus extension; use graduated, gentle compressions, and if you see thrombus in a segment, record it and avoid repeatedly compressing that same segment. Augment with color flow, Valsalva, and respiratory phasicity rather than relying on compression alone. In late pregnancy, avoid prolonged flat supine positioning, which causes hypotension from uterine compression of the inferior vena cava; use a left lateral tilt and examine the left common femoral vein from a left lateral decubitus position. Scan the symptomatic leg first while she is comfortable, and keep total scan time short.
3. What must be documented and communicated after the event?
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The report must state which segments were examined, which were not, that the study was interrupted by presyncope at a specific point, and the vital signs and interventions at the time. Do not describe a partial study as complete. Because she is pregnant, symptomatic, and has a real possibility of proximal DVT, telephone the referring team directly rather than relying on a routine report queue, and state what remains to be done and why. Document the advice given about rescheduling: a longer appointment slot, hydration and a snack beforehand, scanning in a lateral tilt with frequent position changes, and having a companion present. Record the event in the safety log per departmental policy, and consider whether the pre-procedural history of fainting during blood draws should have triggered preventive positioning at the start.