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.

Paramedics in high-stress simulation: performance may be affected

In a recent study from Toronto, researchers studied paramedics in two similar scenarios. Both scenarios involved a 50 year old patient suffering from chest pain. The patient develops pulmonary edema, hypotension and an ECG reveals a STEMI. All study participants (paramedics) performed interventions based on their established local protocols.

In the “high stress” scenario, there was an actor playing the patient’s partner who was visibly distressed and challenging the paramedic’s actions. Also, all alarms were turned up to full volume and there was constant 2-way radio communication going on in the background. None of this occurred in the “low stress”  scenario.

Paramedics were assessed using a global rating scale, a checklist scale and their salivary cortisol levels were measured before and after each scenario (as a response to stress).

The authors noted that “When faced with clinically relevant stressors, paramedics demonstrated significant increases in subjective (anxiety) and physiological
(salivary cortisol) measures of stress. These stress responses were accompanied by impairments in some aspects of clinical performance and in the ability to accurately recall information from the case. Although the paramedics demonstrated no impairments in
their ability to complete each individual action required for the particular scenario, decreased scores on the global rating scale indicate that overall they did so more poorly, with less organization and poorer communication or interpersonal skills.” 

Overall, paramedics did feel more stressed in the “high stress” scenario – this was measured both by a survey and cortisol levels. And while they were able to complete all relevant tasks, their global performance assessment was reduced as was their ability to recall specific case details.

Fascinating study! We must recognize the high potential for error among clinicians when faced with stress.This data should guide us towards the increasing use of emergency checklists so that things are not forgotten in stressful environments,  Such findings will lead nicely into a new video by Scott Orman about the use of whiteboards in handovers and the potential for inaccurate data transmission (unless there’s protocols in place to document better!).

These authors also did a similar study with residents – with similar findings! We need to do better as clinicians & educators in recognizing stress as a huge factor leading to errors and implement interventions to manage these potential threats and errors.

Here’s the abstract

The impact of stress on paramedic performance during simulated critical events.Prehosp Disaster Med. 2012 Aug;27(4):369-74. Epub 2012 Jul 25. Leblanc VR, Regehr C, Tavares W, Scott AK, Macdonald R, King K.

Abstract

OBJECTIVES:

Substantial research demonstrates that the stressors accompanying the profession of paramedicine can lead to mental health concerns. In contrast, little is known about the effects of stress on paramedics’ ability to care for patients during stressful events. In this study, we examined paramedics’ acute stress responses and performance during simulated high-stress scenarios.

METHODS:

Twenty-two advanced care paramedics participated in simulated low-stress and high-stress clinical scenarios. The paramedics provided salivary cortisol samples and completed an anxiety questionnaire at baseline and following each scenario. Clinical performance was videotaped and scored on a checklist of specific actions and a global rating of performance. The paramedics also completed patient care documentation following each scenario.

RESULTS:

The paramedics demonstrated greater increases in anxiety (P < .05) and salivary cortisol levels (P < .05) in response to the high-stressscenario compared to the low-stress scenario. Global rating scores were significantly lower in the high-stress scenario than in the low-stress scenario (P < .05). Checklist scores were not significantly different between the two scenarios (P = .12). There were more errors of commission (reporting information not present in the scenario) in the patient care documentation following the high-stress scenario than following the low-stress scenario (P < .05). In contrast, there were no differences in omission errors (failing to recall information present in the scenario) between the two scenarios (P = .34).

CONCLUSION:

Clinical performance and documentation appear vulnerable to the impact of acute stress. This highlights the importance of developing systems and training interventions aimed at supporting and preparing emergency workers who face acute stressors as part of their every day work responsibilities.

Full text pdf is available here (secure area limited to ADHB staff only – ADHB has subscription access for staff to these journals through the Philson Library at the University of Auckland School Of Medicine)