Previously, I posted about “other people” wearing perfectly good lead aprons lifting them up to their chin during portable xrays in the trauma bay. Is that really necessary, or is it just an urban legend?
After hitting the medical radiation physics books (really light reading, I must say), I’ve finally got an answer. Let’s say that the xray is taken in the “usual fashion”:
- Portable technique in your trauma bay
- Tube is approximately 5 feet above the xray plate
- Typical chest settings of 85kVp, 2mAs, 3mm Al filtration
- Xray plate is 35x43cm
The calculated exposure to the patient is 52 microGrays. Most of the radiation goes through the patient onto the plate. A very small amount reflects off their bones and the table itself. This is the scatter we worry about.
So let’s assume that the closest person to the patient is 3 feet away (1 meter). Remember that radiation intensity diminishes as the square of the distance. So if the distance doubles, the intensity decreases to one fourth. By calculating the intensity of the small amount of scatter at 3 feet from the patient, we come up with a whopping 0.2 microGrays. Since most people are even further away, the dose is much, much less for them.
Let’s put it perspective now. The background radiation we are exposed to every day (from cosmic rays, brick buildings, etc) amounts to about 2400 microGrays per year. So 0.2 microGrays from chest xray scatter is less than the radiation we are exposed to naturally in about 44 minutes!
The bottom line: unless you need to work out you shoulders and pecs, don’t bother to lift your lead apron every time the portable xray unit beeps. It’s a waste of time and effort, unless you are dealing with xray imaging on a very regular basis! And that 52 microGrays the patient absorbed? That’s 8 days worth of background radiation.
Trauma Team members typically wear a lead gown under their standard precautions so they don’t have to run out of the room
when x-rays are taken. How often do you see people do this?
Is it really necessary? Tomorrow I’ll talk about how much radiation team members are really exposed to.
In my previous post, I described a young man who had recovered from a stab to the heart. He did well for a week and a half, but then presented to the ED with significant chest pain. It seems to be substernal and somewhat pleuritic. What should you do to work it up further?
There have been a number of helpful comments. The first order of business is to rule out problems which may prove to be life threatening. In his case, ischemic disease and some failure of the repair must be ruled out quickly. Although ischemia or MI are unlikely in this young man, they are possible and should be evaluated.
I recommend the following:
- Auscultate the chest and heart (remember this from medical school?)
- PA chest x-ray
- FAST exam focusing on the heart
My list is short and simple, and should help me figure out nearly all significant problems.
In this case, the following findings are present:
- The lungs are clear, and their is a faint cardiac friction rub
- The chest x-ray is unremarkable
- EKG shows ST elevations in two of the lateral leads only. Otherwise, it is normal.
- CBC is normal with the exception of WBC 14,000
- There is a trace level of troponin present
- FAST demonstrates a very small pericardial effusion without clot
So what do you make of all this? What’s the diagnosis? What do you need to do? Tweets and comments please.
Here’s an interesting case for you to pick apart!
A 25 year old man is involved in some sort of violent, non-productive interpersonal relationship. He sustains a stab to the left chest, and is brought to your trauma center as a trauma team activation. During the FAST exam, a moderate effusion with visible clot is seen in the pericardium.
Appropriately, you run to the OR and prepare for a left thoracotomy. You perform a pledgeted repair of the ventricle and close. The patient does well and is discharged home five days later. He returns to your clinic the following week and is doing well. You remove the staples.
One week later, he returns to your emergency department complaining of significant chest pain. He describes it as deep, behind his sternum, and it seems to be exacerbated by breathing.
Now what? What are you thinking about? What additional exam do you need. What labs?
Tweet or comment with your answers and suggestions. More on Monday!
With the implementation of resident work hour restrictions more than 10 years ago, resident participation in clinical care has declined. In order to make up for this loss of clinical manpower and expertise, many hospitals have added advanced clinical providers (ACPs, nurse practitioners and physician assistants). These ACPs are being given more and more advanced responsibilities, in all clinical settings. This includes performing invasive procedures on critically ill patients.
A recent study from Carolinas Medical Center in Charlotte NC compared complication rates for invasive procedures performed by ACPs vs residents in a Level I trauma center setting.
A one year retrospective study was carried out. Here are the factoids:
- Residents were either surgery or emergency medicine PGY2s
ACPs and residents underwent an orientation and animal- or simulation-based training in procedures
- All procedures were supervised by an attending physician
- Arterial lines, central venous lines, chest tubes, percutaneous endoscopic gastrostomy, tracheostomy, and broncho-alveolar lavage performances were studied
- Residents performed 1020 procedures and had 21 complications (2%)
- ACPs performed 555 procedures and had 11 complications (2%)
- ICU and hospital length of stay, and mortality rates were no different between the groups
Bottom line: Resident and ACP performance of invasive procedures is comparable. As residents become less available for these procedures, ACPs can (and will) be hired to take their place. Although this is great news for hospitals that need manpower to assist their surgeons and emergency physicians, it should be another wakeup call for training programs and educators to show that resident education will continue to degrade.
Reference: Comparison of procedural complications between resident physicians and advanced clinical providers. J Trauma 77(1):143-147, 2014.