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.

Have we been taught all wrong?…A new location of needle decompression?

Where do you insert the needle for pneumothorax decompression?

Easy!

Is it time to rethink 2nd intercostal space, mid clavicular line for site of needle decompression?

Is it time to rethink 2nd intercostal space, mid clavicular line for site of needle decompression?

“2nd intercostal space (ICS), mid-clavicular line (MCL)” – this has been drilled into all of us since we began training and caring for critically ill patients. Ever since we began as pre-hospital care providers or took our first  Advanced Trauma Life Support have we used the 2nd ICS, MCL and assumed it to be optimal.

Well recently some studies have started looking at whether we should consider an alternative location. There is some evidence to suggest that the traditional anterior approach may reduce kinking and in the combat environment, it might be preferred (Beckett A et al. J Trauma 2011). However, if it will never enter into the pleural space then kinking becomes irrelevant.  While the utility of needle decompression vs. simple finger thoracostomy followed by chest tube insertion can be debated, in the pre-hospital setting, needle decompression remains within the realm of paramedics and may at times be most practical. Also, unless you’re rapidly prepared to perform a chest tube with sterility in mind, needle decompression may be a better option. Thus, such studies remain important.

A recently published study (from the USC trauma surgeons in Los Angeles who seem to publish everything related to trauma) compared the 2nd ICS , MCL with the 5th intercostal space, anterior axillary line (AAL).

CT chest exams of 120 trauma patients were used in the study. Measurements were taken at both sites and compared. Interestingly, the authors stratified patients into 4 BMI categories then analyzed the data based on these groupings.

Results

  • Overall, the 5th ICS AAL was a superior site for needle decompression based on chest wall measurement
  • Chest wall thickness was thicker at the 2nd ICS MCL compared to the 5th ICS AAL (by 0.5cm)
  • As only 16% of patients had chest walls thicker than the standard 5cm needle commonly used. Compared to 42% probable failures if placed at the 2nd ICS MCL.
  • Based on BMI stratification, needle decompression at the 5th ICS AAL would be possible for all but the highest BMI while at the 2nd ICS MCL would likely fail except in the lowest group

Take home message – given this was not a clinical study (only based on CT scans) it’s not quite practice changing. We don’t know the potential risks of cardiac injury using the 5th ICS AAL or whether it can be feasibly performed without kinking. However, this technique could be considered if the 2nd ICS MCL fails, especially in high BMI patients and clearly any benefits outweigh the risks – for instance if the patient has already arrested.

STUDY ABSTRACT

Inaba K et al Radiologic evaluation of alternative sites for needle decompression of tension pneumothorax. Arch Surg 2012;147:813-8

OBJECTIVE: To compare the distance to be traversed during needle thoracostomy decompression performed at the second intercostal space (ICS) in the midclavicular line (MCL) with the fifth ICS in the anterior axillary line (AAL).

DESIGN: Patients were separated into body mass index (BMI) quartiles, with BMI calculated as weight in kilograms divided by height in meters squared. From each BMI quartile, 30 patients were randomly chosen for inclusion in the study on the basis of a priori power analysis (n = 120). Chest wall thickness on computed tomography at the second ICS in the MCL was compared with the fifth ICS in the AAL on both the right and left sides through all BMI quartiles.

SETTING: Level I trauma center.

PATIENTS: Injured patients aged 16 years or older evaluated from January 1, 2009, to January 1, 2010, undergoing computed tomography of the chest.

RESULTS: A total of 680 patients met the study inclusion criteria (81.5% were male and mean age was 41 years [range, 16-97 years]). Of the injuries sustained, 13.2% were penetrating, mean (SD) Injury Severity Score was 15.5 (10.3), and mean BMI was 27.9 (5.9) (range, 15.4-60.7). The mean difference in chest wall thickness between the second ICS at the MCL and the fifth ICS at the AAL was 12.9 mm (95% CI, 11.0-14.8; P < .001) on the right and 13.4 mm (95% CI, 11.4-15.3; P < .001) on the left. There was a stepwise increase in chest wall thickness across all BMI quartiles at each location of measurement. There was a significant difference in chest wall thickness between the second ICS at the MCL and the fifth ICS at the AAL in all quartiles on both the right and the left. The percentage of patients with chest wall thickness greater than the standard 5-cm decompression needle was 42.5% at the second ICS in the MCL and only 16.7% at the fifth ICS in the AAL.

CONCLUSIONS: In this computed tomography-based analysis of chest wall thickness, needle thoracostomy decompression would be expected to fail in 42.5% of cases at the second ICS in the MCL compared with 16.7% at the fifth ICS in the AAL. The chest wall thickness at the fifth ICS AAL was 1.3 cm thinner on average and may be a preferred location for needle thoracostomy decompression

The first ARHT case-based learning session!

This past week, we conducted the first ARHT case-based learning session for the duty crew!

While “case-based learning” may seem like a bunch of educational jargon…it can be rephrased to “sit around the table, discuss a previous job and consider the “what if” “.

I think at this point I was trying to convince people that I wasn't full of BS!

I think at this point I was trying to convince people that I wasn’t full of BS!

We assembled the team for the day which included the crewman, paramedic and doctor for a 45-50 minute session in the board room.  A huge thanks to Russell C, Leon, and Scott O. who all participated and they generated a great discussion about several aspects of this case. (next time we’ll be looking to get our pilot involved too!)

I had the opportunity to facilitate the session which was based on a relatively straight forward job that I had selected. The job involved a patient with a head injury and the focus was on the management of traumatic brain injury in the pre-hospital setting. But amazingly, the discussion covered tons of ground and we discussed all different aspects from before we leave the base, to the time we arrive at the hospital. Much of the discussion focused on CRM ideas which was very interesting.

Our team's paramedic and crewman in deep thought! We must have just been getting to the interesting part! At least the team isn't asleep!

Our team’s paramedic and crewman in deep thought! We must have just been getting to the interesting part! At least the team isn’t asleep…

Here’s a summary of our lively discussion!

Pre-job briefing: unless it was a water job (or extra equip is required) that this could/should be done en route
On scene time: Something we need to address as a team given some growing evidence that scene time doesn’t impact mortality in blunt trauma
Decision making for RSI: time to hospital played considerable role in whether to perform an RSI
Role assignment in RSI: crewman should probably be tasked with RSI checklist and scene management rather than involved in being hands-on during RSI. The doctor should hand the bougie & endotracheal tube to paramedic though  good discussion resulted about this and may be situation dependent
Team position in flight: discussion whether person who intubated should remain at head of bed (even if it was MD) during flight. Consensus that if patient is requiring infusions etc…then MD should be at the side, with paramedic at the head and crewman to his right.

We’ll be looking to roll out a few more sessions in the new year.

Some feedback from the session regarding logistics

  • Using previous jobs to generate discussion is good
  • Focus will be on picking jobs at random to improve learning but this will NOT be a means of quality assurance or control
  • Short sessions will be the goal: 20-30 minutes
  • Getting the whole team together is best, that includes the pilots!
  • All members felt this was a valuable exercise and would participate in future sessions

Again, thanks to the duty crew that day and Scott O for the pictures. See you all in the New Year.