Does every patient who gets pre-hospital needle decompression need a chest tube?

The authors of a recent study tried to answer this question. The authors evaluated patients who got needle decompression in the field using prospective, observational methodology (though I wonder if truly prospective given the lack of data). Anyways, they noted that in their population very few patients (5/52 decompressions) escaped without requiring a follow-up chest tube. Only 1/15 penetrating trauma patients did not get a chest tube.  A few important questions remain including how many of the needle decompressions actually reached the pleural cavity or the technique used for decompression (appears later in Q&A that it was probably anterior axillary line). 

The authors conclude to have a low threshold for chest tube insertion based on CXR however, not shockingly a CT chest will provide more information. This study certainly doesn’t support withholding a chest drain if needle decompression is performed in the field. There was a nice suggesting by another surgeon who commented they leave all the needles in place during CT scan to see if it actually reached the pleural cavity. For the stable patient that doesn’t need immediate intervention, this is probably sound advice. Wait for the CT then make decision based on clinical and radiographic data.

There should probably be further study on this topic but for now, this is all we have! Here’s the abstract below.

Is routine tube thoracostomy necessary after prehospital needle decompression for tension pneumothorax? KM Dominguez et al. Am J Surg 2013; 205(3): 329-332 

BACKGROUND:

Thoracic needle decompression is lifesaving in tension pneumothorax. However, performance of subsequent tube thoracostomy is questioned. The needle may not enter the chest, or the diagnosis may be wrong. The aim of this study was to test the hypothesis that routine tubethoracostomy is not required.

METHODS:

A prospective 2-year study of patients aged ≥18 years with thoracic trauma was conducted at a level 1 trauma center.

RESULTS:

Forty-one patients with chest trauma, 12 penetrating and 29 blunt, had 47 needled hemithoraces for evaluation; 85% of hemithoraces required tube thoracostomy after needle decompression of the chest (34 of 41 patients [83%]).

CONCLUSIONS:

Patients undergoing needle decompression who do not require placement of thoracostomy for clinical indications may be assessed using chest radiography, but thoracic computed tomography is more accurate. Air or blood on chest radiography or computed tomography of the chest is an indication for tube thoracostomy.

Inattentional Blindness – does this apply to pre-hospital medicine?

A recent study (not sure if it’s been published yet but will be soon) studied the ability of radiologists to accurately identify abnormalities on a CT scan. We’re talking board-certified, full fledged radiologists! I can’t take credit for coming across this paper – check out @TechnicalSkillz, ED physician in Toronto who tweeted the link. He has a real interest in cognitive biases and medical decision making. Anyways…I digress.

gorilla CT scan

This image was presented to radiologists after they were told to look for abnormalities including lung nodules. Do you see the abnormality? Don’t worry…you don’t need to be an expert at reading CTs…it should be obvious!

24 radiologists examined this image and 20 were not able to identify the gorilla in the upper right corner! 20/24 didn’t see it! that’s unbelievable. They’re so focused on looking for other things that they glazed right over it. Using eye tracking technology, the reserachers were able to show that impressively 12 looked directly at the gorilla but still they didn’t see it!

This concept of inattentional blindness (or perceptual blindness) is

failure to notice an unexpected stimulus that is in one’s eyesight when other attention demanding tasks are being performed (Wikipedia)

I think this happens not infrequently in pre-hospital medicine and the emergency department. How many times does the patient turn out to have an entirely different presentation from what we hear over the radio call out or what’s written on the triage note. Right from the beginning we’re biased by the what we hear…it may be the local clinic calls with “a 73yr old with pneumonia”. Maybe there’s some shortness of breath to reaffirm this diagnosis but just as the radiologists were looking for nodules, we might be looking for pneumonia and miss the pneumothorax because we didn’t find out the patient fell earlier today. It could have been obvious if we just auscultated the lungs more closely but because we were thinking about crackles, we didn’t anticipate there would be absent breath sounds.

I think we’re especially vulnerable in the pre-hospital setting to inattentional blindness. We receive limited and often wrong information. Add that to time pressures to reduce scene times and it’s very easy to succumb to such cognitive biases.  We must implement cognitive checks to ensure that diagnoses are not missed. Standardized approaches to common presentations can help to ensure that critical diagnoses are considered regardless of the presentation. Efforts to ensure strong team communication will also enhance diagnostic abilities – maybe someone else on your team saw something you didn’t but failed to mention it.

Awareness of pitfalls around diagnostic errors must extend to pre-hospital clinicians. This will help us identify those gorillas! Check out some of the work by Pat Croskerry who’s a world leader in medical decision making, cognitive biases and diagnostic error (plus he’s Canadian, so he must be great!). Please note, the author of this post is Canadian which may be the reason for this conflict of interest!

 

Prehospital Ultrasound – a new tool for our HEMS community

Several months ago, our HEMS service introduced a portable ultrasound machine onto our helicopters and so far it has been a great success!  While this blog post won’t be presenting the data we’re collecting, our physicians have reported it to be extremely useful. Most often we use it in the evaluation of a trauma patient to perform an eFAST (extended focused assessment with sonography in trauma) that includes assessment for free fluid in the abdomen but also importantly, lung ultrasound for the diagnosis of pneumothorax. Recently, I was part of a mission to transport a patient who had suffered a fall and there was question of a pneumothorax as reported by the ambulance team on scene. We were quickly able to perform an ultrasound of the lungs which ruled out pneumothorax. This enabled our pilot to fly at normal altitude rather than having to fly lower. Furthermore, as a clinician, it helped with decision making during transport as the patient still required treatment in hospital for other injuries. Knowledge that a pneumothorax was virtually unlikely allowed me to focus on other treatment priorities.

Picture of a similar model portable ultrasound that is being used at ARHT by HEMS physicians

We’re using a similar model of portable ultrasound as pictured above at ARHT 

More recently, one of our physicians performed an ultrasound guided femoral nerve block to assist with pain management of a patient with a femur fracture. It worked brilliantly and the patient was transported with considerably less pain!

In the spirit of our new technology, I’ve reviewed what’s out there in the literature regarding prehospital ultrasound (and emphasis on HEMS). There’s very little but this is definitely a growing field!

A recent review of HEMS pre-hospital ultrasound feasibility was published with good results. They performed 144 pre-hospital scans. On average scans took less than 2 minutes with a symptom based approach to what region to scan. While there are some limitations in their methodology, they reported no false-positives compared with available clinical data which is important. In addition, overall sensitivity was 85% (though it should probably be reported for each indication). Nonetheless, this study adds support to the feasibility of prehospital HEMS ultrasound and documents what findings may be value in the field. In several cases, management was altered, for example when pneumothorax was diagnosed then chest drains were placed.

Another study just published, prospectively evaluated the utility of lung ultrasound in non-trauma patients with dyspnea in a pre-hospital setting. They used a focused approach (as pictured below) to specifically identify potential causes of dyspnea. In 68% of cases, physicians reported lung US as a useful tool.

Imaging sites for rapid assessment of lung using ultrasound in dyspneic patients in prehospital setting

Imaging sites for rapid assessment of lung using ultrasound in dyspneic patients in prehospital setting

They required physicians to complete the exam within 5 minutes as not to delay scene times. Pneumothorax was accurately ruled out in all cases, while a large pericardial effusion causing hemodynamic instability was properly diagnosed though it was only drained once in hospital. You might imagine however that if the patient deteriorated en route that emergent pericardiocentesis would probably be the next intervention so identification would be important.

Algorithm for evaluation of dyspneic patient in the prehospital setting with ultrasound

Algorithm for evaluation of dyspneic patient in the prehospital setting with ultrasound in conjunction with imaging sites of above picture. 

I’m not sure how to interpret their results when they reported that additional management approaches were taken in 25% of cases as a result of US. Primarily diuretics were administered after US given the diagnosis of pulmonary edema. In our setting, we don’t carry furosemide so this doesn’t directly apply though if perhaps properly delineating between pulmonary edema and COPD would be useful as nitroglycerin vs. nebulizers could be emphasized in subsequent therapy.

I believe that most of the benefit of prehospital ultrasound is in the injured patient however, as we see, there is growing evidence that it can be used similarly to how it’s used within the emergency department and ICU.

References

1.  Eur J Emerg Med. 2010 Oct;17(5):254-9. doi: 10.1097/MEJ.0b013e328336ae9e. Prehospital ultrasound in emergency medicine: incidence, feasibility, indications and diagnoses. Hoyer HX et al.

2. Eur J Emerg Med 2012 Jun;19(3):161-6. doi: 10.1097/MEJ.0b013e328349edcc. Prehospital chest emergency sonography trial in Germany: a prospective study. Neesse A et al.