How Many Chest X-rays Would It Take….

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    How Many Chest X-rays Would It Take….

    A young woman presents to the Emergency Department with chest pain of sudden onset while blowing up a balloon at her kid’s birthday party.

    Vitals are normal but due to slightly decreased breath sounds on the left, you are concerned for pneumothorax. ECG is normal. No other complaints.

    You order a chest x-ray but the radiologist calls to inform you that you can’t get the study until the patient is proven to be without child (beta-HCG negative is a requirement in most institutions for a chest X-ray).

    She just urinated and does not need labs and wants to just get her chest x-ray already. She wants to know if she can skip the bHCG test.

    1. Can we skip the bHCG test and get that Chest Xray?

    2. How many chest X-rays would it take to confer teratogenicity in a pregnant woman? (i.e. how many mRads does a CXR confer, and what is the maximum tolerated dose during pregnancy?

    3. Are there any guidelines that discourage the requirement of requiring a pregnancy test before CXR?

     

    1. Always follow your hospital and department protocol. Some places will allow you to perform a CXR without  negative pregnancy test but you must document the risks and benefits. Other institutions have stricter protocols.

    2. A single CXR confers 0.07 mRAD of radiation. The maximum tolerated dose is 5000 mRAD. Therefore 5000 mRAD/ 0.07 mRAD= 71,428 chest X-rays. Assuming each CXR takes 1 minute to set-up and acquire, a patient would have to continuously have chest X-rays for 49 straight days to reach the maximum tolerated dose in pregnancy.

    3. No. Despite the lack of genuine medical risk, no one has stated that it is a waste of ED resources and patient time to require this. Perhaps this should be assessed.

    Below is an image from the American Academy of Family Physicians showing radiation risk with various modalities. The one providers should be aware of is CT abdomen. A pregnant patient should probably receive <2 CT abdomen and pelvis studies during pregnancy, though some protocols can decrease the mRAD exposure.

    Afp19990401p1813-f1

     

    Some statements are encouraging, but nothing from ACEP so far.

    Key Statements on Diagnostic Imaging Modalities During Pregnancy (reminder: 5 Rads= 5000 mRADs)

    X-ray imaging
    “No single diagnostic procedure results in a radiation dose that threatens the well-being of the developing embryo and fetus.“— American College of Radiology 3
    “[Fetal] risk is considered to be negligible at 5 rad or less when compared to the other risks of pregnancy, and the risk of malformations is significantly increased above control levels only at doses above 15 rad.”— National Council on Radiation Protection5
    “Women should be counseled that x-ray exposure from a single diagnostic procedure does not result in harmful fetal effects. Specifically, exposure to less than 5 rad has not been associated with an increase in fetal anomalies or pregnancy loss.”— American College of Obstetricians and Gynecologists7

     

    Resources:

    http://www.guideline.gov/search/search.aspx?term=pregnancy+and+x-ray

    Safety of Radiographic Imaging During Pregnancy: Am Fam Physician. 1999 Apr 1;59(7):1820.

     

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