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General

Does Chest Tube Size Matter? Part 2

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In my last post, I reviewed a large prospective series comparing smaller (28-32 Fr) to larger (36-40 Fr) chest tubes for management of pneumothorax. The authors did not detect any significant difference because the study was underpowered given the incidence of the adverse events examined.

Today, I’ve chosen a more recent paper that attempts to do the same thing. Interestingly, it cites the previous paper as a good example showing no differences! This one is from an emergency medicine group in Fukui, Japan. It is a retrospective review of seven years worth of patients who had a chest tube inserted for hemothorax only.

Here are the factoids:

  • Small bore tubes were 20-22 French, and large bore tubes were 28 French (huh?)
  • The tube selection was made (once again) at the discretion of the attending physician
  • Demographics and injury data from the two groups were equal
  • A total of 124 tubes were placed in 116 patients, 68 small bore and 56 large bore
  • Empyema occurred in 1% in each group
  • Retained hemothorax occurred in 2% of small tube patients and 3% of large tube patients
  • An additional tube was placed in 2% of small tube patients and 7% of large tube patients (p = 0.41)
  • Pain was not evaluated

The authors concluded that “emergent insertion of the small-bore tubes had no difference in efficacy of drainage, complications or need for additional invasive procedures.”

Bottom line: Huh? Once again we have an inferior design (retrospective review) and huge potential for selection bias (no criteria or randomization for tube size). But in this case, the tube sizes are very similar! The difference in diameter between a 20 Fr tube and a 28 Fr one is only 2.5mm! Reason #1 for no apparent differences.

For reason #2, look at the sample size. First of all, this hospital placed only 124 tubes in 7 years. That’s a one tube every three weeks. Is there that little chest trauma, or is a chunk of data missing? This sample size is less than half of that in the previous post, so the statistical power is far weaker. Look at the stats above for additional tube placement. A 3.5x change was not even close to being statistically significant. In fact, this sample size would not show a significant difference for retained hemothorax until one group had nearly 8x the number! No wonder the authors assumed there was no difference. The study was not designed in such a way that it could ever show one!

So throw this study in the trash bin, too. I’ll continue my search for a more convincing “size matters” paper in my next post.

And if you think you’ve got one, send it my way so I can have a look!

Reference: Small tube thoracostomy (20-22 Fr) in emergent management of chest trauma. Injury 48(9):1884-1887, 2017.

Thorax

Does Chest Tube Size Matter? Part 1

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Over the next few days I will be reviewing a number of papers that try to determine whether the dogma that bigger chest tube size is better is actually true.

Here are the questions that need to be answered when reading each one to determine if it’s worth its weight:

  • How good is the study design? Obviously, prospective is better than retro. How did the authors decide to put in a small vs a large tube? Were there enough subjects to achieve any meaningful statistical significance?
  • Were the tubes used actually different? If the small bore tubes are 30 – 32 French and the large tubes are 36 – 40 French, would that make a difference?
  • What were the outcomes studied? Mortality and complications like pneumonia and empyema are too crude and uncommon to detect a difference. But what about incidence of retained hemothorax, accidental removal, subjective pain, or clotting?
  • Did the authors identify and acknowledge any limitations in their study?
  • Do the conclusions match up with the actual results?

Let’s kick off the chest tube size debate with an oldie but goodie. The first paper I’ll review was published back in 2012 by a busy LA trauma center.  They performed a prospective, observational study of their experience with two tube size ranges inserted for hemo- and pneumo-thorax over a three year period. The size ranges were 28-32 for small and 36-40 for large. The size selected was based on the discretion of the attending physician.

A total of 353 chest tubes were placed during the study period. This analysis will only dissect the 275 that were inserted for hemothorax.

Here are the factoids:

  • Pertinent demographics were identical for the large and small bore tube patients
  • Pneumonia occurred in about 5% of both groups, and empyema in about 5% of both
  • Retained hemothorax occurred in 12% of small tubes and 11% of large tubes
  • Duration of tube placement was about 6 days in each
  • Additional procedures such as thrombolysis, additional chest tubes, VATS, or thoracotomy were 3-6% in both groups and were not statistically different
  • Pain scores could only be performed on about 45% of patients, and were not different between the two groups

The authors concluded that there were no differences in complications, tube reinsertion, or need for invasive procedures based on tube size. They also concluded that choice of tube size did not impact outcomes.

Bottom line: The authors seem to be saying that the choice of tube size is not important. And if you only read the abstract or conclusions of this study, you might actually believe it. But wait, the authors end the paper with this telltale sentence:

“Further evaluation of percutaneously placed drainage systems is warranted”

This is code for: “this paper isn’t very good and shouldn’t change your practice; it needs further verification.”

So what are the issues?

  • There is huge potential for selection bias since the choice of tube size was based on personal preference. For example, the attending could look at the chest x-ray, see a lot of blood, and decide to use a big tube in that patient. No guidelines or randomization were used.
  • The authors did not acknowledge any limitations of the study in their discussion.
  • The only outcomes that really counted in this study were incidence of retained hemothorax (which was not very well defined) and additional procedures required. However, if you take the incidence of retained hemothorax in the large bore tube patients and do an analysis of the statistical power of the study, you run into a major problem. Given the number of patients in each of the two groups, this study would only be able to show statistical significance if the number of retained hemothoraces in the small chest tube group doubled! Anything short of 25% retained hemothorax in the small tube group would not be significant. Thus, the authors’ findings that there was no difference between the groups was entirely expected based on sample size. 

So this paper does not really say that there is no difference in using a small vs a large chest tube. It says that it was not sufficiently powered to detect anything but a massive difference. Many more patients (thousands) were needed to answer the question.

So the question remains, does (chest tube) size matter? More in the next post.

Reference: Does size matter? A prospective analysis of 28-32 versus 36-40 French chest tube size in trauma. J Trauma 72(2):422-427, 2012.

Thorax

Chest Tube Insertion: Does Size Matter?

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I’m old school. I cut my teeth during the days when there were only two sizes of chest tubes for trauma: big and bigger. That meant 36 French or 40 French. Period. I even went as far as adding a chest tube insertion video to my collection of YouTube posts:

But recently, someone posted a comment on that video to the effect that we are moving away from large chest tubes for trauma.

But are we? Really? Am I missing something? I’ve written a few posts in the last two years, examining some of the newer research on this topic. One paper was so-so, one was terrible.

So I’ve decided to really hit this topic hard this week. I want to know what the literature really says on this topic. So I’ve located the best papers I could and I’m going to do a teardown over the next few days. That way I can make sure that my video is up to date, and that my (and your) practice is as well.

Tomorrow, I’ll start with work that compares large and smaller bore tubes. Through the week, I’ll work my way down in size to papers suggesting that pigtail catheters are as good as a chest tube.

Hope you enjoy! We’ll all learn something!

Resuscitation

Massive Transfusion: What’s The Right Ratio?

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In my last post, I analyzed a survey that studied the massive transfusion protocol (MTP) practices of academic Level I trauma centers in the US. What centers do is one thing. But what does the literature actually support? A group from Monash University in Melbourne, Australia and the National Health Service in the UK teamed up to review the literature available through 2016 regarding optimal dose, timing, and ratio of products given during MTP.

One would think that this was easy. However, the search for high quality ran into the usual roadblock: the fact that there is not very much of it. The authors scanned MEDLINE for randomized, controlled studies on this topic, and found very few of them. Out of 131 articles that were eligible, only 16 were found to be suitable for inclusion, and 10 of them were still in progress. And only three specifically dealt with the ratio question. Even they  were difficult to compare in a strict apples to apples fashion.

Here are the factoids that could be gleaned from them:

  • There was no difference in 24-hour or 30-day mortality between a ratio of 1:1:1 (FFP:platelets:RBC) vs 1:1:2
  • However, a significantly higher number of patients  achieved hemostasis in the 1:1:1 group (86% vs 78%)
  • There was no difference in morbidity or transfusion reactions in the two groups
  • One study compared 1:1 component therapy with whole blood transfusion and found no difference in short-term or long-term mortality or morbidity

Bottom line: As usual, the quality of available data is poor if one limits the field to randomized, controlled studies. Ratios of 1:1:1 and 1:1:2 appear to be equally effective given the limited information available. A number of papers not included in this review (because of their less rigorous design) do seem to indicate that higher ratios of RBC (1:3-4) appear to be detrimental. And as time passes, more and hopefully better studies will be published.

What does this all mean for your MTP? Basically, we still don’t know the best ratio. However, it is recommended that your final ratios of FFP:RBC end up somewhere between 1:1 and 1:2. The only way to ensure this is to set up your MTP coolers so the the ratio of product they contain is better than 1:2. This means more plasma than 1 unit per 2 units of red cells. 

If you set it at the outside limit of 1:2, then that is the best ratio you can ever get assuming everything goes perfectly. However, if you have to thaw frozen plasma, use too much emergency release PRBC before activating MTP, or someone cherry-picks the coolers to transfuse what they think the patient needs, the ratios will quickly exceed this boundary.

So be sure to load your coolers with ratios that are closer to 1:1 to ensure that your final ratios once MTP is complete are what you want them to be. And monitor the final numbers of every one of your MTP activations through your trauma performance improvement program so you know what your patients are really receiving.

Reference: Optimal Dose, Timing and Ratio of Blood Products in Massive
Transfusion: Results from a Systematic Review. Transfusion Med Reviews 32:6-15, 2018.

Guidelines

Massive Transfusion: What Ratios Are People Using?

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This is the first of a two-part series on massive transfusion protocol (MTP) ratios. Today, I’ll write about what ratios trauma centers around the country are using. Tomorrow I’ll review the literature we have to date on what the correct ratio should be. Are we all doing the right thing or not?

Back in the old days (which I remember fondly), we didn’t pay too much attention to the ratio of blood to plasma. We gave a bunch of bags of red cells, then at some point we remembered that we should give some plasma. And platelets? We were lucky to give any! And to top it all off, we gave LOTS of crystalloid. Turns out this was not exactly the best practice.

But things have changed. Some good research has shown us that a nice mix of blood component products is good and too much crystalloid is bad. But what exactly is the ideal mix of blood products? And what is everybody else doing? I’ll try to answer these questions in this series.

So first, what are all the other trauma centers doing? An interesting medley of anesthesia and pathology groups from the University of Chicago, a Dallas-based anesthesia group, and a blood center in my home base of St. Paul, conducted a survey of academic medical centers in 2016. They wanted to find out how many actually had a MTP and to scrutinize the details.

They constructed a SurveyMonkey survey and sent it to hospitals with accredited pathology residencies across the US. There were 32 questions in the survey, which asked for a lot of detail. As you can probably personally attest, the longer and more complicated the survey, the less likely you are to respond. That certainly happened here. Of 107 surveys sent out, it took a lot of nagging (initial email plus two nags) to get a total of 56 back.

Here are the factoids:

  • Most were larger hospitals, with 74% having 500 or more beds
  • All had massive transfusion protocols
  • Trauma center level: Level I (77%), Level II (4%), Level III (4%), Level IV (2%), no level (14%)
  • Nearly all (98%) used a fixed ratio MTP; very few used any lab-directed (e.g. TEG/ROTEM) resuscitation
  • Target RBC:plasma ratio: 1:1 (70%), 1.5:1 (9%), 2:1 (9%), other (9%)
  • Only 58% had the same RBC:plasma ratio in each MTP cooler
  • More than 86% had thawed plasma available (remember, these were generally large academic centers)
  • Half stored uncrossmatched type O PRBCs outside the blood bank, usually in the ED; only 1 stored thawed plasma in the ED
  • A total of 41% had more than one MTP (trauma, OB, GI, etc.)
  • 84% had some type of formal review process once the MTP was complete
  • About 68% had modified their MTP since the original implementation. Some increased or decreased ratios, expanded MTP to non-trauma services, decreased the number of units in each pack, changed to group A plasma from AB, or switched from ratio to TEG/ROTEM or back.

Bottom line: This is an intriguing snapshot of MTP practices around the country that is about four years old. Also remember, this is a somewhat skewed dataset. The survey was directed toward hospitals with academic pathology programs, not trauma centers. However, there is enough overlap that the results are probably generalizable. 

Most centers are (were) using MTP packs containing six units of PRBCs, and were attempting to achieve a fixed 1:1 ratio. Half of hospitals had the same number of units in each cooler, half varied them by cooler number. Nearly half had multiple flavors of MTP for different specialties. Very few used TEG/ROTEM during the initial phased of MTP. Most modified their MTP over time.

I’ve written quite a lot on most of these issues. See the links to my “MTP Week” series from earlier this year, below.

Tomorrow, I’ll review what we know and don’t know about the proper ratios to use in your MTP.

Reference: Massive Transfusion Protocols: A Survey of Academic
Medical Centers in the United States. Anesth & Analg 124(1):277-281, 2017.

MTP week series: