How To Evaluate A Stab To The Diaphragm – Part 1

Penetrating injury to the diaphragm, and specifically stab wounds, have been notoriously hard to diagnose since just about forever. Way back in the day (before CT), we tried all kinds of interesting things to help figure out if the patient had a real injury. Of course, we could just go to the OR and lap the patient (laparoscopy did not exist then). But the negative lap rate was significant, so we tried a host of less invasive techniques. 

Remember diagnostic peritoneal lavage? Yeah, we tried that. The problem was that the threshold for red cells per cubic mm was not well defined. Some would supplement this technique with a chest tube to see if lavage fluid would drain out. And one paper described instilling nuclear medicine tracer into the abdomen and sitting the patient under a gamma camera for a few hours to see if any ended up in the chest. Groan!

We thought that CT would save us. Unfortunately, resolution was terrible in the early years. If you could actually see the injury on CT, it was probably because a large piece of stomach or colon had already fallen through it. But as detectors multiplied and resolution improved, we could begin to see some smaller defects. But we still missed a few. And the problem is that left-sided diaphragmatic holes slowly enlarge over time (years), until the stomach or colon falls through it. (See below)

A group of radiologists and surgeons in a Turkish trauma hospital recently published a modest series of patients with left-sided diaphragm injuries evaluated by CT. They looked at about 5 years of their experience in a group of patient who were at risk for the injury due to a thoraco-abdominal stab wound. Unstable patients were immediately taken to OR. All of the remaining patients underwent an initial CT scan, followed by diagnostic laparoscopy after 48 hours if they remained symptom free.

Here are the factoids:

  • A total of 43 stable patients with a left thoraco-abdominal stab were evaluated
  • 30 patients had a normal CT, and 13 had the appearance of an injury
  • Of those who were CT positive, only 9 of 13 (69%) actually had the injury at operation
  • Two of the 30 (7%) who were CT negative were found to have a diaphragm injury during followup laparoscopy
  • So in the author’s hands, there was 82% sensitivity, 88% specificity, a positive predictive value of only  69%, and a negative predictive value of 93%

Bottom line: The authors somehow looked at the numbers and concluded that CT is valuable for detecting left diaphragm injury. Huh? They missed 7% of injuries, only finding them later at laparoscopy. And they had a 31% negative laparotomy rate. 

Now, it could be that the authors were using crappy equipment. Nowhere in their paper do they state how many detectors, or what technique was used. Since it took place over a 5 year period, it is quite possible that the earlier years of the study used equipment now considered to be out of date, or that there was no standardized technique.

CT may not yet be ready for prime time. But it can be a valuable tool. Tune in tomorrow for some tips on how and when to look for this insidious injury.

Related post:

Reference: Evaluation of diaphragm in penetrating left thoracoabdominal
stab injuries: The role of multislice computed tomography. Injury 46:1734-1737, 2015.

The Cost Of Duplicate Radiographic Studies

Duplicate radiographic studies are a continuing issue for trauma professionals, particularly after transfer from a smaller hospital to a trauma center. The incidence has been estimated anywhere from 25% to 60% of patients. A lot has been written about the radiation dangers, but what about cost?

A Level II trauma center reviewed their experience with duplicate studies in orthopedic transfer patients retrospectively over a one year period. They looked at the usual demographics, but also included payor, cost information, and reason for repeat imaging. Radiation dose information was also collected.

Here are the factoids:

  • 513 patients were accepted from 36 referring hospitals
  • 48% had at least one study repeated, 256 CT scans and 161 conventional imaging studies
  • Older patients and patients with low GCS were much more likely to receive repeat studies
  • There were no association with the size of the referring hospital or the ability of the patient to pay
  • Most transfers had commercial insurance; only 11% had Medicaid and 17% were uninsured
  • Additional radiation from repeat scans was 8 mSv. The average radiation dose from both hospitals was 38 mSv. This is 13 years of background radiation exposure!
  • The cost of all the repeat studies was over $96,000

Bottom line: This is an eye-opening study, particularly regarding how often repeat imaging is needed, how much additional radiation is delivered, and now, the cost. And remember that these are orthopedic patients, many of whom had isolated bony injuries. I would expect that patients with multiple and multi-system injuries would require more repeat imaging and waste even more money. It is imperative that all centers that receive transfers look at adopting some kind of electronic data transfer for imaging, be it a VPN or some cloud-based service. With the implementation of the Orange Book by the American College of Surgeons, Level I and II centers will receive a deficiency if they do not have some reliable mechanism for this.

“Level I and II facilities must have a mechanism in place to view radiographic imaging from referring hospitals within their catchment area (CD 11–42).”

Reference: Clinical and Economic Impact of Duplicated Radiographic Studies in Trauma Patients Transferred to a Regional Trauma Center. J Ortho Trauma 29(7):e214-e218, 2015.

Why We Can’t Just Stop Anticoagulants In Trauma Patients

We’ve all been faced with injured patients who are taking some kind of anticoagulant, and it complicates their care. Why can’t we just stop them in patients at risk for injury (e.g. an elderly patient who falls frequently)?

Two major risk groups come to mind: those taking the meds who have DVT (or a propensity to get it), and patients with atrial fibrillation who take them to decrease stroke risk. I was not able to find much info (yet) on the former category. But there is a series of nicely done studies based on work from the Framingham Heart Study.

The Framingham study started in 1948, and has been following over 5,000 people for the development of cardiovascular disease. In this particular analysis, 5070 patients who were initially free of disease were analyzed for development of atrial fib and occurrence of stroke. Anticoagulants were seldom used in this group.

The authors found that the prevalence of stroke increased with age in patients with atrial fib. The percentage that could be attributed to a-fib also increased. The following summarizes their numbers:

  • Age 50-59: 0.5 strokes per 100 patients, attributable risk 1.5%
  • Age 60-69: 1.8 strokes per 100 patients, attributable risk 2.8%
  • Age 70-79: 4.8 strokes per 100 patients, attributable risk 9.9%
  • Age 80-89: 8.8 strokes per 100 patients, attributable risk 23.5%

Bottom line: The risk of having a stroke just because a patient has atrial fibrillation goes up significantly with age. So setting an age cutoff for taking an anticoagulant doesn’t make sense. Unfortunately, increasing age also means increasing risk of injury from falls. Warfarin definitely cuts that risk, and it happens to be relatively easily reversbile. However, the newer non-reversible drugs change the equation, shifting the risk/benefit ratio too far toward the dark side. We need some good analyses to see if it really makes sense to move everybody to these new (expensive) drugs just to make it easier to dose and monitor. The existing studies on them only look at stroke, but don’t take injury morbidity and mortality into account.

Reference: Atrial fibrillation as an independent risk factor for stroke: the Framingham study. Stroke 22:983-988, 1991.

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Novel Hip Reduction Technique: The Captain Morgan

I wrote about posterior hip dislocation and how to reduce it using the “standard” technique quite some time ago (see link below). Emergency physicians and orthopedic surgeons at UCSF-Fresno have published their experience with a reduction technique called the Captain Morgan.

Named after the pose of the trademark pirate for Captain Morgan rum, this technique simplifies the task of pulling the hip back into position. One of the disadvantages of the standard technique is that it takes a fair amount of strength (and patient sedation) to reduce the hip. If the physician is small or the patient is big, the technique may fail.

In the Captain Morgan technique, the patient is left in their usual supine position and the pelvis is fixed to the table using a strap (call your OR to find one). The dislocated hip and the knee are both flexed to 90 degrees. The physician places their foot on the table with their knee behind the patient’s knee. Gentle downward force is placed on the patient’s ankle to keep the knee in flexion, and the physician then pushes down with their own foot, raising their calf. Gentle rotation of the patient’s hip while applying this upward traction behind the patient’s knee usually results in reduction.

Some orthopedic surgeons use a similar technique, but apply downward force on the patient’s ankle, using the leverage across their own knee to develop the reduction force needed. The Captain Morgan technique use the upward lift from their own leg to develop the reduction force. This may be gentler on the patient’s knee.

The authors report a series of 13 reductions, and all but one were successful. The failure occurred due to an intra-articular fragment, and that hip had to be reduced in the operating room.

I’m interested in hearing comments from anyone who has used this technique (or the leverage one). And does anyone have any other techniques that have worked for them?

Related post:

Reference: The Captain Morgan technique for the reduction of the dislocated hip. Ann Emerg Med (in press) dol:1016/j.annemergmed.2011.07.010, 2011.