In my last post, I wrote about proper screening for blunt cerebrovascular injury (BCVI). But, as you know, it’s important to screen only when there is a significant risk of the injury being present. Screening using the shotgun approach (screen everyone for everything) yields enough false positive results to present potential danger to your patient.
A variety of authors on this topic have promoted a number of high risk criteria to trigger a screening test. Most make sense, and are related to the anatomy of the vessels in question. The carotid arteries are relatively unprotected, although a bit deep, as they course up the neck. Thus, it is possible to damage them when they suffer a direct and significantly hard blow. Once they enter the skull, they are better protected. However, fractures through key areas of the skull base and face can injure the vessels, even in these protected locations.
The vertebral arteries are deep and relatively protected as they course through the vertebral foramina. However, if the vertebrae are fractured or subluxed, vessel injury can occur.
Finally, and as always, the physical exam is important. If there are unexpected neurologic changes that can’t be explained by other injuries, or there are indications of deep vascular injury, BCVI needs to be considered.
Here is my list of indications to screen for BCVI:
- Neurologic abnormality not explained by diagnosed injury
- Arterial epistaxis
- Seat belt sign on neck
- GCS < 8 (this is the most commonly forgotten one)
- Petrous bone fracture
- C‐spine fracture (C1‐C3) or subluxation at any level
- Fracture through foramen transversum
- LeFort II or III fractures
Bottom line: Be on the lookout for any of the criteria listed above in your trauma patient. If you find one during your initial evaluation, be sure to order a CT angiogram of the neck. And keep an eye out while scanning the head and cervical spine. If any of the other radiographic indications become apparent, add on the CT angiogram at that point.
Blunt injury to the carotids or vertebrals (BCVI) is a little more common than originally thought, affecting about 1% of blunt trauma patients. We have many tools available to help us diagnose the problem: duplex ultrasound, CT angiography (CTA), MR angiography (MRA), and even good old conventional 4 vessel angiography.
But which one is “best?” This is a tough question, because there is always some interplay between clinical accuracy and cost. The surgical group at the Medical College of Wisconsin – Milwaukee did a nice job teasing some answers from existing literature on the topic. The authors tried to take a comprehensive look at costs, including money spent to prevent stroke, the cost of complications of therapy, and the overall cost to society if the patient suffers a stroke.
Here are the factoids:
- For patients at risk for BCVI, the stroke rate is 11% without screening, 6% with duplex ultrasound screening, 4% with MRA, and 1% with either CTA or conventional angiography
- From a societal standpoint (includes the lifetime costs of stroke for the patient), CTA is the most cost effective at $3,727 per patient
- From the hospital standpoint (does not include lifetime cost), no screening is the most cost effective, but has the highest stroke rate (11%)
- CTA prevents the most strokes, and costs about $10,000 per patient while decreasing societal costs by about $32,000 per patient screened
Bottom line: The “best” test for patients at risk for blunt cerebrovascular injury is the CT angiogram. It minimzes the stroke rate, and provides information on all four vessels supplying the brain, which is probably why the duplex ultrasound has a higher miss rate (can’t see the vertebrals or into the skull). But how do you decide who is at risk for this problem? Tune in to the next post!
Reference: Screening for Blunt Cerebrovascular Injuries is Cost-Effective. J Trauma 70(5):1051-1057, 2011.
Most stable patients with blunt trauma undergo CT scanning these days. Hopefully, it’s done thoughtfully to optimize the risk/benefit ratio using a well-designed imaging protocol. The majority of these torso imaging protocols call for the use of IV contrast. But as I’ve written before, this can pose risks, especially to the elderly and others who have some degree of renal impairment.
Unfortunately, I occasionally encounter scans done at other hospitals that omit the use of contrast. This usually hinders diagnosis significantly. And it’s usually not clear why this happened, so let’s think about it a bit.
The use of contrast in CT is designed to show blood, or things that are filled with lots of blood. Specifically, a great deal of detail about the blood vessels and solid organs is displayed.
Let’s break it down by type of scan:
- Chest – we are really only interested in the aorta. The only way to reliably demonstrate an aortic injury is by using contrast. And this is one of those injuries that, if you miss it, the patient is very likely to die from it. Therefore, if you are ordering a chest CT properly, you must add contrast.
- Abdomen/pelvis – generally, we are looking for solid organ injury, potential mesenteric injuries, and extravasation of blood from organs or soft tissue. Once again, the only way to really see any of these is with contrast enhancement.
- Vascular – CT is replacing conventional angiography for the investigation of vascular injury in many cases. Obviously, this study is worthless without the contrast.
Bottom line: Pretty much any CT of the chest, blood vessels, or abdomen/pelvis must have IV contrast injected for accurate diagnosis. But what if your patient is old, or is known to have some degree of renal impairment? First, decide if you can wait until a point of care or standard creatinine measurement is done. If you can, use the result to do your own risk/benefit calculation. Is the injury you are worried about potentially life-threatening AND reasonably likely? Are there other less harmful ways to detect it? Then use them. And if you really do need the study in a patient with renal dysfunction, give the contrast, monitor the serum creatinine regularly, and do what you can to optimize and protect their renal function over the next several days.
Here’s one in a series of “When To Call” pieces. We sometimes overuse our consultants and call then at inappropriate times. So what if we diagnose an injury in their area of expertise at 2 am? Does it need attention or an operation before morning? If not, why call at that ungodly hour?
Let’s use our consultants wisely! I’ve listed most of the common urologic diagnoses that trauma professionals will encounter. There is also an indication of what you need to do, and exactly when to call your consultant.
Here’s a reference sheet formatted at a 3×5 index card that you can keep in your pocket. I’ve included a printable pdf file, as well as the original Microsoft Publisher file in case you want to make a few modifications to suit your own hospital.
When to call Urology reference card (pdf)
When to call Urology MS Publisher file (pub)
Yesterday, I detailed some pelvic binders commonly available in the US. Today, I’ll go through the (little) science there is regarding which are better than others.
There are a number of factors to consider when choosing one of these products. They are:
- Does it work?
- Does it hurt or cause skin damage?
- Is it easy to use?
- How much does it cost?
It’s difficult to determine how well binders work in the live, clinical setting. But biomechanical studies can serve as a surrogate to try to answer this question. One such cadaver study was carried out in the Netherlands a few years ago. They created one of three different fracture types in pelvis specimens. Special locator wires were placed initially so they could measure bone movement before and after binder placement. All three of the previously discussed commercial binders were used.
Here are the factoids:
- In fracture patterns that were partially stable or unstable, all binders successfully closed the pelvic ring.
- None of the binders caused adverse displacements of fracture fragments.
- Pulling force to achieve complete reduction was lowest with the T-POD (40 Newtons) and highest with the SAM pelvic sling (120 Newtons). The SAM sling limits compression to 150 Newtons, which was more than adequate to close the pelvis.
So what about harm? A healthy volunteer study was used to test each binder for tissue pressure levels. The 80 volunteers were outfitted with a pressure sensing mat around their pelvis, and readings were taken with each binder in place.
Here are the additional factoids:
- The tissue damage threshold was assumed to be 9.3 kPa sustained for more than 2-3 hours based on the 1994 paper cited below.
- All binders exceeded the tissue damage threshold at the greater trochanters and sacrum while lying on a backboard. It was highest with the Pelvic Binder and lowest with the SAM sling.
- Pressures over the trochanters decreased significantly after transfer to a hospital bed, but the Pelvic Binder pressures remained at the tissue damage level.
- Pressures over the sacrum far exceeded the tissue damage pressure with all binders on a backboard and it remained at or above this level even after transfer to a bed. Once again, the Pelvic Binder pressures were higher. The other splints had similar pressures.
And finally, the price! Although your results may vary due to your buying power, the SAM sling is about $50-$70, the Pelvic Binder $140, and the T-POD $125.
Bottom line: The binder that performed the best (equivalent biomechanical testing, better tissue pressure profile) was the SAM sling. It also happens to be the least expensive, although it takes a little more elbow grease to apply. In my mind, that’s a winning combo. Plus, it’s narrow, which allows easy access to the abdomen and groins for procedures. But remember, whichever one you choose, get them off as soon as possible to avoid skin complications.
- Comparison of three different pelvic circumferential compression devices: a biomechanical cadaver study. JBJS 93:230-240, 2011.
- Randomised clinical trial comparing pressure characteristics of pelvic circumferential compression devices in healthy volunteers. Injury 42:1020-1026, 2011.
- Pressure sores. BMJ 309(6959):853-857, 1994.