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Saturday, August 31, 2013

4 things to know before you needle the chest.

Looking for a tension pneumothorax (PTX), and especially deciding to perform a needle decompression, can trip up even the most smartest EMS provider. There's a balance between the need for aggressiveness, and the wisdom of careful monitoring.


Ok, that was too aggressive - dial it back next time.
A few recent cases brought into Bridgeport Hospital, as well as some recent research, help us refine the approach to evaluation and treatment. 4 fun facts about tension PTX!

1. It's rare!
While some authors have described a 6% rate of tension PTX in prehospital trauma patients, the rate is probably far lower in most U.S. EMS systems, with some estimating it happens in fewer than 0.3% of blunt trauma patients.

Another study, published in 2013, found that about 1% of the trauma patients coming into a Level 1 center had received a needle by EMS for a suspected PTX, and that most of them ended up getting a chest tube in the ED or OR. 

Problem is, they weren't able to tell if the patients had had a tension PTX when EMS needled them, or just a plain ol' pneumo. So, at worst, 1% of severe trauma patients have a tension PTX.

2. Paramedics have trouble identifying it.
That last study showed that  paramedics are pretty good at diagnosing a pneumothorax. How good are they at diagnosing the tension part?


A study done in Nashiville looked at 19 patients who got a needle decompression by EMS for suspected tension. About 1/4 of those patients were proven to have any sort PTX (tension or not), and only 2/14 of the living patients were considered to have had a tension PTX (based on finding an air leak after placing a chest tube).
So, only 14% of patients who got a needle actually had a tension PTX

3. Diminished lung sounds & crepitus ≠ tension
A patient can have complete collapse of a lung, and still not need a needle!

A few months ago one of the medics was concerned that they hadn't treated a trauma patient as aggressively as he should have. The patient had fallen a few days prior, and was complaing of shortness of breath. The medic noted bruising over the chest, paradoxical chest wall motion, and absent lung sounds. Nevertheless, the patient was breathing better on 2 lpm of oxygen, and the vitals were fine.

In the ED, the patient was promptly sent to the CT scan...
Pneumthorax, as well as subcutaneous air
... and got a chest tube right away! So the medic was concerned - should they have placed a needle in the field?

It doesn't sound like it. It's important to remember why a tension pneumo is bad. Progressive collapse of the lung leads to hypoxia, and the rise in intrapleural pressures compress the IVC, leading to hypotension. In other words, patients don't die from a pneumothorax - they die from hypoxia and shock. Rogue Medic wrote about this at some length, and you might enjoy his take on the subject.

So if subcutaneous emphysema and absent lung sounds don't require you to decompress, what signs should? A very thorough (and free!) review article from 2005 provided a list of the signs that trauma experts agree could warrant EMS attempting to decompress.

Just remember - hypoxia and hypotension!

Source
(Keep in mind that you should be suspecting tension pneumothorax - don't needle the patient with bradypnea, pinpoint pupils, and track marks just because she's hypoxic with a decrease LOC.)

It's only helped in one case report.

4. Your needle may be too short (or your patient too big...)
So, another medic brought in a trauma patient, thrown from a motorcycle, with pain over the left chest, and absent lung sounds as well. The medic had already needled the chest with the standard 14g IV catheter, but reported that lung sounds were still absent.

Sounded like a no-brainer to me; if the patient hadn't already needed a chest tube before, now they most likely did (since a needle decompression can also cause a pneumothorax). But when the patient was rolled into the trauma bay, we found no pneumo on chest x-ray, ultrasound, or even CT. Heck, looking at the CT, we realized there was no way the stubby 14 g ever made it near the lung!

This is a very common experience - unless you have a special long catheter, you may not be able to reach the pleural space, especially in the standard "midclavicular, 2nd intercostal space" that we've been taught. Why? Because we're all getting bigger, and the catheters are not!

A standard 14g iv catheter; 2" or 5 cm,

Seems big at first, but take a look at where we're trying to put this needle:

People can be thick, both in the 2nd ICS anteriorly (left),
as well as the 5th ICS laterally (right)
(Adapted from Schroeder et al)
That can be a lot of skin, fat and muscle to get through! A standard 5 cm catheter may reach the pleura in most Japanese patients, and some Turkish patients, but only in a minority of Americans.

One option is to place the needle at the 5th ICS, along the anterior axillary line, since there is generally less muscle and fat there than at the traditional 2nd ICS. One study, done in Los Angeles, found that a standard 5 cm (2 inch) needle placed at the 2nd ICS would be too short in 42% of patients, but only in 15% at the 5th ICS.

So, a lateral placement might help, but so might more needle. They make a longer 14 g iv catheter just for decompressing, extra long at 3.25 inches, or 8 cm. Of course, what's the downside of having an extra-long needle shoved into the left side of the chest?

"With a PTX, is the blood supposed to shoot out?"
The Bottom Line
A pneumothorax happens relatively often in severe trauma, but these do not require any specific prehospital treatment. A tension PTX, on the other hand, is rare, difficult to diagnose in the field, and there are some obstacles to treating it appropriately.

You're looking for a patient with not just absent lung sounds, but persistent hypoxia, and worsening hypotension. And when you place the catheter, you have to make sure it's actually reaching the pleura - but not too far in!



7 comments:

  1. Hi guys,

    What is your take on the last points of the 2005 article excerpt?

    "- bilateral finger thoracostamy
    - not needle thoracocentesis"

    ReplyDelete
    Replies
    1. This echoes the sentiments of a lot of the retrieval docs from UK/AU/NZ. "Cut to air."

      Delete
    2. I don't think many non-physician EMS systems are going to endorse fingers over needle for prehospital treatment. Such a rare event, and needles are likely somewhat safer in the hands of a (relative) novice.

      In the truly crashing trauma patient, I agree with a "finger-first" approach, but I'm not doing this at 100 kph on a bumpy road!

      Check out a great podcast on this topic over at EMCrit, and also read the comments.

      Delete
  2. Our local trauma docs actually did a study on this, looking at scans of patient's chest walls and measuring them. They basically advocated for a switch to 3.25" needles, which ended up being concurrent to our State's requirement for needle length.

    All in all the increased education on the topic seems to have decreased their usage, now that we've been made aware of their low likelihood of being useful.

    ReplyDelete
    Replies
    1. Agree. If the indications for empiric decompression attempts were clearer to medics (point #3 above), I think there would be a lot less excitement about "needling" the patient.

      Delete
  3. A very experienced trauma surgeon I knew told a class that using a 14 ga/2 inch needle was basically useless. He was incredibly pro EMS, but he wanted EMS to do things that actually worked. After that we got the 3.25 inch ones, but actual use was incredibly rare.

    I think I did three in 22 years as a paramedic, with no patient surviving.

    ReplyDelete
    Replies
    1. Agree - another case of where a therapy is either under- or over-treating in the vast majority of cases.

      The patients who are critical enough to justify using needle decompression are usually sick enough that you are going to go on and place chest tubes anyway, no matter what (if anything) comes out of the needle.

      The patients who don't look like they need immediate chest tubes probably don't need a needle immediately either.

      Delete