All posts by TheTraumaPro

Best Of EAST 2020 #2: Do Platelet Transfusions Fix Sad Platelets?

The next abstract from EAST tackles the question of how we can treat platelets that don’t work right in trauma patients. The literature on using platelet transfusions in patients who are taking anti-platelet agents is getting fairly clear: they don’t work. But what about for platelets that don’t work right due to traumatic hemorrhage?

The trauma group at Penn attacked this problem by performing a prospective study at their Level I trauma center. They investigated platelet function using thromboelastography (TEG) with platelet mapping on trauma patients admitted to the intensive care unit over a two year period. They analyzed platelet function and counts at 3, 6, 9, 12, and 24 hours after admission. Platelet function in patients given platelets during any of the intervals were compared to those who were not. Outcomes studied were improvement in platelet function and mortality.

Here are the factoids:

  • A total of 93 patients were entered into the study
  • About half (57%) had platelet dysfunction detected by TEG
  • Mortality was not different between the groups
  • Neither platelet count nor function improved with transfusion

The authors concluded that platelet dysfunction is common in these patients and that platelet transfusions do not appear to restore platelet function.

My comment: This abstract is a bit hard to follow. Hopefully the manuscript will have more detailed tables that break down which patients got platelets and at what times. It appears that patients could have gotten platelets at various times (any, all, or none) after admission to the ICU, and that pre- and post-transfusion TEG runs were analyzedfor each. It’s also not clear if every patient with dysfunction got a transfusion.

The most obvious issue here is that the total number of patients is small, and the numbers getting platelets at each time interval is even smaller (10-49). The statistical power of such a study is very low. It’s not surprising that no significant differences could be detected. This means that failing to see significance doesn’t means it’s not necessarily there, just that many more patients are needed. So it’s hard to buy into the assertion that platelet transfusions don’t matter.

Here are my questions/comments for the presenter:

  1. Why didn’t all patients get platelets? From the table, it looks like nearly all patients had significant dysfunction (defined as MAadp < 40mm) until the end of the 24 hour study period. It looks like some selection bias is possible if there was no defined protocol for giving transfusions to those who had an abnormal TEG.
  2. Is your study sufficiently powered to draw the conclusion it did? The number of patients seems small overall, and doing measurements serially every 3 hours would seem to further weaken the statistics. Please comment on your choice of analysis and how likely you are to actually be able to detect significance.
  3. Be sure to clarify the details of when platelets were given and why, how many measurements were taken and when, and exact patient numbers. These are not clear in the abstract due to length limitations.

This paper is very interesting and I look forward to its presentation.

Reference: Platelet infusions do not correct trauma induced platelet dysfunction. EAST Annual Assembly abstract #24, 2020.

Best Of EAST 2020 #1: Treatment Of Blunt Carotid & Vertebral Injuries

The 33rd Annual Assembly of the Eastern Association for the Surgery of Trauma starts in just two weeks! As usual, I will select several interesting abstracts from the bunch to review. I’ll go over the findings of the research, critique it, and then provide a series of questions for the presenter to consider. These questions are ones that members of the audience may very well ask (hint, hint).

And FYI, I always send a heads-up to the presenters with a link to the post so they can study up beforehand!

So let’s get started with the first abstract that will be kicking off the meeting on January 15. Blunt cerebral / vertebral artery injury (BCVI) is one of those insidious injuries that trauma professionals don’t always think about. But they do occur in about 1% of major trauma patients. It’s one of those injuries that can’t be ignored because very serious complications may occur if it is not treated appropriately (think stroke).

Unless there are extenuating circumstances like bleeding or pseudoaneurysm, treatment is usually pharmaceutical. There are two camps: antiplatelet drugs vs anticoagulant drugs. But there is very little data to determine which one is better.

This abstract is a retrospective review from the National Readmission Database (NRD). This resource is maintained by the US government and provides information on patient readmissions nationally across all payors as well as the uninsured. They included all patients > 18 years old with a BCVI and minor injuries in other body regions. Patients who suffered a stroke complication during their initial hospital stay were excluded.

Patients were divided into two groups: those taking an antiplatelet agent and those prescribed an anticoagulant. Outcomes of interest were readmission with CVA and death, within six months.

Here are the factoids:

  • 725 patients with BCVI were found during the five year study period
  • Patients were propensity matched for a 1:1 ratio of patients taking antiplatelet vs anticoagulant drugs, leaving 370 patients for analysis
  • There was a lower rate of admission in the anticoagulant patients vs the antiplatelet ones (9% vs 26%)
  • There were fewer deaths within 6 months in the anticoagulated patients (1.3% vs 3.9%)
  • Median time to stroke was 6-9 days and was not significantly different between the two groups

The authors concluded that the overall stroke rate after BCVI is 6%. They also found an association with lower rates of CVA within 6 months of discharge in patients on anticoagulants. They recommend further studies to determine which type of chemoprophylaxis is best.

My comments: This is an interesting paper that addresses a problem that we don’t have good answers for. The study was well constructed and simple to follow. The two areas that I have questions about are data quality and statistical power.

The NRD is a powerful tool for research, but does have some shortcomings. It only contains information on readmissions, and may not contain some patients who had asymptomatic strokes or massively stroked and died at home. Not knowing these numbers injects some bias and could change the numbers and findings of the study.

The other issue has to do with statistical power. The overall eligible patient group (725 patients) was small in the first place. Propensity matching for a 1:1 ratio shrunk it to only 370, or 185 in each treatment group. My armchair power calculations show that this study would only be able to detect a 7x difference in mortality, and not the 3x difference seen. I’m glad the authors didn’t claim a “significant decrease in CVA” in the anticoagulated patients vs the antiplatelet drug patients.

Here are my questions for the authors:

  1. What do you see as drawbacks to data quality in your study due to use of the National Readmissions Database? How do you think that patients not included in it impacted your data?
  2. Is there anything you can do to improve the statistical power of the study to see if the mortality difference is truly different? Even though your statistical analysis shows significance, the number of subjects doesn’t allow you to claim this until the mortality in the antiplatelet group reaches 9%. 

This was a simple yet fascinating study, and is a start toward helping us determine which of the two drug classes is most appropriate for patients with BCVI.

Reference: Treatment of blunt cerebrovascular injuries: anticoagulants or antiplatelets? EAST Annual Assembly abstract #1, 2020.

If A Tree Falls In A Forest…

It’s time for a little philosophy today. There seem to be two camps in the world of initial diagnostic testing for trauma: selective scanning vs pan-scanning. I admit that I am one of the former. Yes, the more tests you do, the more things you will find, and this will make your radiologist happy. Some of these findings will be red herrings. Some may be true positives, but are they important? Here’s the key question:

“If a tree falls in a forest and no one is around, does it make a sound?”

Huh? How does this answer my question? Well, there is a clinical corollary to this question in the field of trauma:

“If an injury exists but no one diagnoses it, does it make a difference (if there would be no change in treatment)?”

Here’s an example. On occasion, my colleagues want to order diagnostic studies that won’t make any clinical difference, in my opinion. A prime example is getting a chest CT after a simple blunt assault. A plain chest xray is routine, and if injuries are seen or the physical exam points to certain diagnoses, appropriate interventions should be taken. But adding a chest CT does not help. Nothing more than the usual pain management, pulmonary toilet, and an occasional chest tube will be needed, and those can be determined without the CT.

Trauma professionals need to realize that we don’t need to know absolutely every diagnosis that a patient has. Ones that need no treatment are of academic interest only, and can lead to accidental injury if we look for them too hard (radiation exposure, contrast reaction, extravasation into soft tissues to name a few). This is how we get started on the path to “defensive medicine.”

Bottom line: Think hard about every test you order. Consider what you are looking for, what you might find, and if it will change your management in any way. If it could, go ahead. But always consider the benefits versus the potential risks, or what I call the “juice to squeeze ratio.”

References:

  • George Berkeley, A Treatise Concerning the Principles of Human Knowledge, 1734, section 45.
  • paraphrased by William Fossett, Natural States, 1754.

Mainstem Intubation In Pediatric Patients: How To Avoid It

In my last post, I reviewed a simple technique utilizing a reminder card and provider feedback loops to reduce deep intubations in pediatric patients. Today, I’ll review three other techniques and discuss a paper that compared their efficacy.

A variety of techniques for determining and/or confirming endotracheal tube position exist. Use of one or more of them is important in children due to their short trachea and increased likelihood of deep intubation. Some, like the confirmatory chest x-ray, are obvious. However, it’s more desirable to apply techniques during the intubation in order to avoid deep intubation in the first place. Hyperinflation of one lung, especially in very small children, can cause a host of impairments and complications that may compound their other injuries.

A paper from the University Hospital Basel in Switzerland evaluated three techniques: bronchoscopic insertion to a specific depth, cuff palpation in the sternal notch, and intentional right mainstem intubation followed by slow withdrawal during auscultation.  Each of 68 children ranging in age from 0 to 4 years were studied using all three techniques.

Each endotracheal tube was marked at the ideal insertion point that would ideally be placed just beyond the vocal cords. The distance from this mark to the mouth end of the tube was measured so actual intubation depths could be compared.

Bronchoscopic insertion was always performed first to obtain a baseline depth measurement, essentially the gold standard. The other two techniques were performed in random order. For the cuff palpation technique, the trachea was palpated while the balloon was intermittently partially inflated until it could be felt at the suprasternal notch. For the mainstem intubation technique, the uninflated tube was advanced until breath sounds in the left axilla disappeared. It was then slowly withdrawn until sounds reappeared.

Distances from the tip of the tube to the carina was calculated using the insertion depth at the incisors and the initial ideal intubation depth mark. Here are the factoids:

  • Insertion to a depth mark on the tube via bronchoscope technique resulted in the highest tube tip with respect to the carina, and also with the greatest depth variability
  • The cuff palpation technique resulted in less distance to the carina (about 19mm vs 36 for the mark technique) and less variability
  • Use of the mainstem intubation with pullback technique resulted in the tube tip resting within just a few mm of the carina, but tube depth was very consistent

Bottom line: What to make of all this? Which technique is “best?” First, it’s not practical or advisable to use a bronchoscope for every pediatric intubation. It’s invasive and adds complexity and time to a critical procedure. The cuff palpation technique also takes additional time due to the repeated cuff inflation/deflation that is required. However, the tube position is fairly accurate and safe.

The intentional right mainstem intubation with pull-back seems a bit sketchy. It requires some type of ongoing ventilation while the tube is being inserted, as well as someone who can listen to the left chest. Additionally, it results in a tube position that is so low that neck positioning may move it into the mainstem bronchus again.

In my mind, estimation of the proper depth pre-intubation is probably the best. Strict attention must be paid to the final depth of the tube once it is inserted, as measured by the distance marker at the incisors. This number must match the one decided upon at the start of the procedure. A good exam of the chest should be carried out to quickly identify an inadvertent mainstem intubation. And finally, a quick confirmatory chest x-ray should always be obtained for objective information on tube position. 

The fancy techniques described in this paper add too much time and complexity for intubation in a trauma situation. They may very well have a place in the OR where the situation is more controlled and there is more advanced equipment and support. But stick to the basics when intubating children in your trauma bay!

Reference: Assessment of three placement techniques for individualized positioning of the tip of the tracheal tube in children under the age of 4 years. Ped Anesthesia 25:379-285, 2014.