How Much Fetal Radiation Exposure In Imaging Studies?

September 26, 2023 The Trauma Pro Leave a comment

I periodically publish a chart that shows how much radiation exposure our patients get from various trauma imaging studies. For reference, here it is:

Test	Dose (mSv)	Equivalent background radiation
Chest x-ray	0.1	10 days
Pelvis x-ray	0.1	10 days
CT head	2	8 months
CT cervical spine	3	1 year
Plain c-spine	0.2	3 weeks
CT chest	7	2 years
CT abdomen/pelvis	10	3 years
CT T&L spine	7	2 years
Plain T&L spine	3	1 year
Millimeter wave scanner (that hands in the air TSA thing at the airport)	0.0001	15 minutes
Scatter from a chest x-ray in trauma bay when standing one meter from the patient	0.0002	45 minutes
Scatter from a chest x-ray in trauma bay when standing three meters from the patient	0.000022	6 minutes

One of the issues that trauma professionals gnash our teeth about is how much radiation the baby gets when we perform these studies on pregnant women. Well, here is just what you need. Another chart! In order to avoid confusion, I will list effective doses to the fetus in milligrays (mGy), which is how much radiation is deposited in a substance. This is a little confusing, since doses are frequently listed in millisieverts which takes the specific organ and type of radiation into effect. In general, these two units are very similar for x-rays.

A useful rule of thumb is that if the fetal dose is less than 50 mGy during any trimester, the risk of an abortion or fetal malformation is about the same as from other risks to the pregnancy. The American College of Radiology notes that exposures less than 100 mGy are “probably too subtle to be clinically detectable.”

To help in your clinical decision making, I’ve added some extra information to the table regarding fetal exposure:

Test	Adult Dose (mSv)	Fetal Dose (mGy)
Chest x-ray	0.1	negligible
Pelvis x-ray	0.1	negligible
CT head	2	<1
CT head and C-spine	4	10
CT chest	7	<1
CT abdomen/pelvis	10	25
Pan Scan (CTA chest, abdomen, and pelvis)	up to 68	up to 56
CT pulmonary angiogram	up to 40	<1

Bottom line: We still have to think hard about how we image pregnant patients! There are some alternatives available to us, including the good old physical exam, conventional x-rays, and ultrasound. MRI is possible, but is a pain in the ass for many reasons.

CT of the head and cervical spine are fine for both mother and baby, and non-contrast imaging of the torso is within accepted limits of fetal exposure. However, the whole point of the torso scan in CT is to identify critical injuries that may lead to exsanguination like solid organ and aortic injuries. In general, those scans should always be ordered with contrast.

If clinical suspicion is high, it may be necessary to order these higher-dose studies anyway. If the mother has an unrecognized and potentially fatal injury, the baby will not survive either. There are many, many permutations of injuries and diagnostics. These cases will put your clinical judgment to the test, for sure!

References:

Imaging Pregnant and Lactating patients. RadioGraphics 35:6, 1751-1765, 2015.
Imaging of the pregnant trauma patient. RadioGraphics 34:3, 748-763,2014.
Fetal doses from radio logical examinations. Br J Radiol;72(860): 773–780, 1999.

Abstracts, Resuscitation

Best Of AAST #8: Whole Blood At The Scene Of Injury

September 21, 2023 The Trauma Pro Leave a comment

Here’s another abstract with a promising title that suffers from low subject numbers. Whole blood is the new darling of trauma resuscitation. Assembling a unit of whole blood from the components it was broken down into produces an inferior product from the standpoint of resuscitation.

It makes sense from a coagulation standpoint, but there are a few pesky issues that need to be considered, such as antibody titers. So I understand the enthusiasm to get some papers out there that describe the value of it.

A group in the Czech Republic performed a prospective study that assigned patients to receive scene resuscitation with either one unit of packed cells plus one unit of plasma, or two units of low titer group O whole blood. They had a host of primary outcomes, including feasibility, 24-hour and 30-day mortality, 24-hour blood use and fluid balance, and initial INR. They compared the two groups to matched cohort controls from a trauma registry. The study was performed over a three year period.

Here are the factoids:

Three groups of about 50 patients each were enrolled
There was no difference in 24-hour mortality, but the authors claimed that the 30-day mortality was “better.” However, the numbers were not statistically significant.
They found a statistically significant decrease in 24-hour transfusion volume of about 500cc, which is not clinically significant
Similarly, there was an increase in fluid balance of about 2L
They also found a “significant” decrease in INR from 1.17 to 1.10, which is also not clinically significant
There were no transfusion reactions

The authors concluded that whole blood was safe to give at the scene and that there were improvements in the measured parameters.

Bottom line: Sorry, but the abstract does not really support the title. This study is woefully small, and confusing to read. The purpose of the registry control cohort was not clear, and the extra results further muddied the picture. The statistical analyses were not included, and I am skeptical that they fully support the conclusions. There is just no statistical power to achieve significance with the number of subjects in this study. And many of the differences, even if they were statistically significant, were not clinically significant.

I don’t want to be a downer here. I do believe that whole blood is a good thing. Unfortunately, the whole blood in this study could have been better used doing a much bigger, multicenter study to truly show us the benefits.

Reference: Whole blood on the scene of injury improves clinical outcome of the bleeding trauma patient. AAST 2023, Plenary paper #28.

Abstracts, Resuscitation

Best Of AAST #7: How Do You Like Your Platelets – Warm Or Cold?

September 20, 2023 The Trauma Pro Leave a comment

Until the last few years, massive transfusion in trauma consisted of component therapy, an admixture of packed red cells, plasma, and platelets. Whole blood transfusion is making inroads again, but it is used in a minority of centers.

Of the three components, platelets have classically required different handling than the others. They are generally kept at room temperature, while the red cells and plasma are kept very cold to preserve their shelf life. A few centers have toyed with the use of cold platelets, but there have been concerns about their ability to clot and their useful life after transfusion.

Researchers from the US Army performed a retrospective registry study on a sample of military casualties over four years. They identified soldiers who received either room-temperature or cold-stored platelets. The primary outcome was mortality, and secondary outcomes included the need for surgery, fluid and blood infusions, and the use of a massive transfusion protocol.

Here are the factoids:

A total of 300 patients were identified, nearly equally split between room temp platelets and cold-stored
Demographics of the two groups were similar, but the ISS was somewhat higher in the cold-stored platelet group
Significantly fewer cold-stored platelet patients underwent surgery (13% vs. 24%)
Survival was the same at 87-88%
Blood and product administration was significantly higher in the cold-stored group, as was the use of the MTP (54% vs. 34%)

The authors concluded that the use of cold-stored platelets were not inferior to room temperature platelets.

Bottom line: Huh?? Yes, survival was the same despite a higher ISS in the cold platelet group. But they required more blood and needed massive transfusion significantly more often.

I see two major issues with this study. The most important is that it is a non-inferiority study. To believe that both arms are equal, a power analysis is required. The sample size here is too small to achieve significance unless differences are extreme, like the transfusion and MTP numbers.

The second problem is that this is an association study. Attempting to show that the type of platelets used is a major determinant of survival, need for surgery, or blood product use is shortsighted. There are a myriad of other factors that have more of an impact.

Far more subjects need to be studied, and a retrospective study with limited data points is not enough. I’m surprised that a military registry could only come up with 75 patients a year to analyze. These low numbers and the nature of this particular registry could inject significant bias as well.

Stay with the room temp platelets for now, and wait for a well-powered prospective analysis before changing your MTP.

Reference: An analysis of the use of cold-stored platelets in combat trauma. AAST 2023 Plenary paper #29.

Abstracts, Complications

Best Of AAST #6: Chronic Disease In Young Trauma Patients

September 19, 2023 The Trauma Pro Leave a comment

Worldwide, the proportion of older people is growing. With that is an increase in the number of older folks with medical comorbidities like diabetes, hypertension, and obesity. Trauma professionals recognize these conditions’ negative impact on recovery after injury.

But is being young becoming the new old? The trauma group at WakeMed performed a retrospective multi-center study to tease out an estimate of the prevalence of these conditions (plus one more: alcohol/substance use) in injured young(er) people. They studied trauma patients aged 18-40 over three years, examining their charts for evidence of the conditions listed that had been previously undiagnosed.

Here are the factoids:

Of the 6,307 patients included, a startling 4,843 (77%) had at least one underlying disease, usually hypertension or obesity
Using their multivariate models, they found that age was (barely) a predictor, as were male sex ( 1.43x) and uninsured status (1.6x)
Only a quarter of patients had a primary care physician (PCP), but this did not increase the presence of underlying disease
Patients found to have these conditions were twice as likely to be referred to a PCP, although this referral rate was still very low (14% vs. 8%)
There was no difference in inpatient complications or hospital length of stay

The authors concluded that the undiagnosed disease burden in young adult trauma patients is high. They recommend rigorous screening measures and appropriate referrals.

Bottom line: This is an interesting abstract revealing what we all probably subconsciously recognize. Younger people are not as healthy as they once were. The numbers with obesity, diabetes, hypertension, and substance use are now staggering, with over three-quarters of patients in this convenience study impacted.

Abnormalities are often found on the lab panels drawn during a trauma activation or upon admission. Unfortunately, we do not always act on them since they don’t appear to have anything to do with the trauma.

This abstract makes it clear that the disease burden in this group is high. It is very likely that those affected will probably develop complications at an earlier age and will suffer a decrease in their overall healthspan as they age. The only and most important thing we can do is pay attention and set our patients up with a primary care physician on discharge to begin working on their potential health problems.

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