Podcast 118 - Obstetric Ultrasound w/ Cynthia Griffin
Anne and Chris are expecting their first child. As they finish their cup of coffee and add a few more names to their "maybe list," they smile knowing today is their baby shower. Anne is a picture of health. She eats clean, takes her gummy bear prenatal vitamins, and has a great relationship with her obstetric (OB) provider.
As they begin their short drive to the baby shower at the community center, a driver swerves into their lane and in an attempt to avoid hitting them, Chris yanks the steering wheel and forces he car off road into a ditch. Terrified, they both look at each other and slowly realize what just happened.
EMS arrives on scene and identifies that Anne & Chris have self-extricated themselves from the car. Besides a few cuts and bruises, they don’t look that bad. It doesn't take long for EMS to spot the fact that Anne is pregnant - probably because she keeps repeating "please tell me if my baby is ok!"
Pause for a second and imagine you are responding to this scene as an ALS intercept. Shortly after arriving you are informed that your patient is 22 weeks pregnant. As you enter the back of the ambulance, the BLS crew gives you the following report:
You look at the monitor and the most concerning thing you see is the battery life and the fact that mom is laying flat. You take a few rolled blankets and place the underneath the right side of the board to displace mom's belly off of the inferior vena cavae.
Anne keeps asking "is my baby ok?!" There may be some momentum to just break out the ultrasound and look for a fetal heart rate RIGHT NOW, but you know that taking care of mom means taking care of baby. It is best not to skip steps in your adult trauma assessment just because your patient is pregnant.
Mom is alert, speaking in full sentences, and there are no signs of external bleeding. She provides you with a quick history and reports no complications so far in the pregnancy.
You ask your partner to grab a glucose and reach for the ultrasound probe to perform a quick E-FAST exam.
My goal for this blog is to focus in specifically on the female pelvic ultrasound. If you are interested in learning more about the entire E-FAST exam, check out this great video by Core Ultrasound
So far, you do not note any free fluid within the peritoneal cavity. The heart is contracting normal/no tamponade and there is beautiful bilateral lung sliding. As you move down the pelvis, you place your probe marker towards the patient's head and slide down below the pubic symphysis.
It is important at this point to not start looking for a baby and chasing a moving target. Systematic movements will help with identifying landmarks. I find that you typically have to go way lower than you think. The first structure you will likely identify in the first and beginning of 2nd trimester is the bladder (if it's not empty). The bladder provides a nice acoustic window into the uterus when full. This is why pregnant women are told not to pee prior to their OB ultrasound appointments. I use the bladder as a reference. Here is a illustrated layout of the gravid uterus during a sagittal pelvic ultrasound.
In the supine female patient, free fluid that makes its way into the pelvic extension of the peritoneal cavity, will likely accumulate between the rectum and uterus. This space is called the "Pouch of Douglas (POD)." On ultrasound the uterus looks like a folded towel to me.
It is important to note that free fluid found on ultrasound does not correlate injury in the location that it is observed. Ectopic pregnancy's will commonly present with free fluid in the right upper quadrant. Here is an example of a non-gravid uterus with free fluid between the uterus and the rectum.
Anne does not have any sonographic signs of free fluid, but she is very concerned about her baby. Now it's time to obtain a fetal heart rate. Before we get into the logistics of obtaining a fetal heart rate, I should mention that a negative EFAST exam does not rule out internal bleeding. In fact, most studies will claim the sensitivity of the EFAST exam to be in the ballpark of 60-70%.
Obtaining Fetal Heart Rate
Now that you have performed a trauma exam and obtained a brief history, we can focus our attention on the fetus. Capturing a fetal heart rate on ultrasound is a great data point when assessing fetal health. This can be performed by identifying the flicking fetal heart and dropping the motion line (M-line) across the moving heart. Anything that touches the line will be measured across a longitudinal axis. By utilizing the fetal heart rate calipers, you can measure from peak to peak and the device will calculate the heart rate.
Talking To Mom
In Anne's case, the baby had a heart rate of 150 and showed great fetal movement. When communicating ultrasound findings with mom, it is best to stay as objective as possible. Communicate objective findings, such as fetal movement and fetal heart rate.
However, how do we communicate if we do not see a heart rate or fetal movement? I asked my friend Cynthia Griffin to come on and discuss this delicate conversation and best practices in regard to communicating what you see on ultrasound with mom. Cynthia is a board-certified emergency physician and works as a flight physician in Wisconsin. I think you all will really enjoy this conversation.
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Blackbourne LH, Soffer D, McKenney M, et al. Secondary ultrasound examination increases the sensitivity of the FAST exam in blunt trauma. J Trauma. 2004;57(5):934-938.
Goodwin H, Holmes JF, Wisner DH. Abdominal ultrasound examination in pregnant blunt trauma patients. J Trauma. 2001 Apr;50(4):689-93; discussion 694. doi: 10.1097/00005373-200104000-00016. PMID: 11303166.
Rowell SE, Barbosa RR, Holcomb JB, Fox EE, Barton CA, Schreiber MA. The focused assessment with sonography in trauma (FAST) in hypotensive injured patients frequently fails to identify the need for laparotomy: a multi-institutional pragmatic study. Trauma Surg Acute Care Open. 2019 Jan 24;4(1):e000207. doi: 10.1136/tsaco-2018-000207. PMID: 30793035; PMCID: PMC6350755.