Yesterday, I wrote about the (unclear) benefits of helicopter EMS transports. Today, I’ll cover the risks. The number of medical helicopters in the US has grown dramatically since 2002.
As can be expected, the number of mishaps should go up as well.
Although it looks like the fatal and injury accidents peaked and then declined, it does not look as good when compared to the rest of the aviation industry. Consequently, being on a helicopter EMS (HEMS) crew has become one of the more dangerous professions.
And unfortunately, the numbers have not improved much during the past five years. So what to do? Make it a big PI project. Approach it systematically, analyze the issues, and create some guidelines and protocols for all to follow.
Tomorrow, I’ll review guidelines for HEMS released by the American College of Surgeons Committee on Trauma.
Reference: Medical helicopter accidents in the United States: a 10 year review. J Trauma 56:1325-1329, 2004.
I’m going to kick off 4 days of information on helicopter emergency medical services (HEMS).
The use of medical helicopters has grown at an astonishing rate in the 10+ years since Medicare got involved with payment for this service. All high level trauma centers have helicopter landing facilities, and many either own or are a part owner in at least one helicopter EMS service (HEMS).
Here’s a state by state breakdown of the number of medical helicopters:
It’s gotten to the point where the indication for summoning a HEMS service seems to be the presence of a patient to ride on it!
A lot of papers have been published in the past 20 years trying to justify the benefits of using these services. As is the usually case when a lot of papers are published on one subject, most of them are not very good. Many studies have been performed to try to justify their use, and most were not successful. The following items have been scrutinized:
Most of these papers found little, if any, benefit. The ones that did tended to be published by institutions that owned these services, raising the significant question of bias. The one thing that was always significantly different was the cost. HEMS costs at least 5-10 times more than ground EMS transport.
So the benefits are not very clear. What about the risks? I’ll talk about those in my next post.
A few months ago, I started to notice a new piece of information coming across on my trauma activation pages: point of care lactate level. I had heard nothing about this prior to these pages, and was curious to know whether this was a new policy/practice, or some study that was in progress. So, of course, I had to do a little bit of reading to find out what was up with that. I’ll share that with you today.
Serum lactate has been used since forever in the inpatient setting, especially in the ICU. It is used as a surrogate for tissue hypoxia and/or metabolic acidosis. A number of studies have found that hypoperfusion is frequently underappreciated, since we tend to use crude vital signs (BP and pulse) which may look normal in early hypovolemia. Serum lactate guided therapy has been shown to improve survival in some studies, and can indicate that resuscitation is proceeding appropriately. Patients who do not show early improvement in their lactate levels are more likely to be refractory to resuscitation, and have higher mortality.
So it would make sense that if prehospital trauma professionals could identify occult tissue hypoperfusion in the field, appropriate resuscitation could start earlier. And nowadays, one can find a point of care device to measure just about anything. Thus, the extra tidbit of information on my trauma pages.
But remember, just because something makes sense doesn’t mean that it actually works. Thus, a group at the University of Birmingham (in the UK) did a systematic review of the literature through 2015, looking specifically at lactate levels obtained in the prehospital setting.
Here are the factoids:
Of the 2,415 articles screened, only 7 were suitable for analysis
These studies were judged to be of “low” or “very low” quality
The methods by which the lactate level were obtained (venous vs capillary), timing, and documentation were highly variable
The authors concluded that there is not yet enough data to support point of care lactate in the field
Bottom line: Point of care lactate drawn in the field would seem to be a good idea. Unfortunately, there aren’t any studies yet that are good enough to make this a standard practice. As with any new technique, if there’s no data then you MUST participate in a well designed study so it can be shown, yea or nay, that the practice is a good one. So join up!
Reference: Prehospital point-of-care lactate following trauma: a systematic review. J Trauma 81(4):748-755, 2016.
This post was requested by one of my EMS colleagues who is the medical director of a rural EMS agency.
Maybe you watched the movie “Signs” by M. Night Shyamalan, starring Mel Gibson. Gibson is a preacher whose wife was killed in a tragic accident. She was running and was pinned against a tree by a pickup truck. She is so badly injured that only the pressure of the truck against her is keeping her alive (and together, apparently). Gibson gets to have a few final words before being extricated (and killed).
Could this really happen?Shouldn’t entrapped people be extricated immediately, or do our prehospital providers need to wait until more advanced medical care is present at the scene?
Here’s the movie clip, if you are interested:
Obviously, you will find NO research on anything like this. The real question is, should EMS first responders (if not medically equipped and able) completely extricate an entrapped patient before paramedics or other trauma professionals with advanced skills are present? In other words, can you die just from being unentangled from the wreckage, like Mel Gibson’s wife?
The answer is, possibly. But it might not be for the reasons you think. Remember, this is Hollywood.
There are two killers upon release from entrapment. First, the mechanism by which the patient is pinned may be holding pressure on things that are or want to bleed. These include the pelvic bones, injuries to the torso, groins, and proximal extremities, and possibly even intra-abdominal hemorrhage sources. I’m discounting the chest because if there is enough pressure to tamponade bleeding, it will probably critically impair hemodynamics and ventilation to the point of killing your patient prior to extrication anyway.
The second factor is a crush injury, with release of a bolus of acidic, potassium laden blood from the crushed extremity upon release. This is probably quite rare, since it takes a significant amount of time for the un- or under-perfused extremity to build up enough of these substances to pose a threat. If the patient has been entrapped for less than 30-60 minutes, there is probably little danger to releasing them.
Bottom line: It is probably best to wait for ALS providers to arrive so IVs can be established and post-extrication resuscitation can be planned. This includes having fluid and/or blood products available in case critical bleeding starts once the pressure has been released. And don’t worry about reperfusion injury unless your patient has been trapped for quite a while.
Unneeded use of helicopter emergency medical services (HEMS) air transport is a problem around the world. This scarce and valuable resource tends to be over-utilized, resulting in unnecessary costs to patients and the health care system in general. Unfortunately, good and objective criteria for HEMS transport have been hard to come by.
A group at the University of Pittsburgh published a study earlier this year, developing an objective scoring system based on a huge dataset from the National Trauma Databank. They used a portion of the data to develop a model, and the remainder to test it. They developed the AMPT, which identified patients that showed a survival benefit with helicopter transport:
For this AAST abstract, they sought to validate the scoring system using an entirely different database, the Pennsylvania Trauma Systems Foundation registry. They used 14 years of data, and reviewed nearly a quarter million records. Once again, the authors were looking at in-hospital survival.
Here are the factoids:
20% of patients were transported by air
But only 11% were predicted to benefit by using AMPT
For patients with an AMPT score < 2, transport by air did not increase survival
For patients who had an AMPT score >2 and were actually transported by air, survival was improved by 31% (!)
Bottom line: It looks like the AMPT score is a good predictor of improved survival for patients transported by air. But wait, it’s not that cut and dried. These statistics are based on populations; they cannot predict exactly which individual patient will benefit. What about those patients who actually died? Perhaps if they had gotten to the hospital a little faster, they would have done better? This is certainly a nice new tool to use in the decision-making process, but it can’t be the only one.
The air medical prehospital triage score: external validation supports ability to identify injured patients that would benefit from helicopter transport. AAST 2016, Paper #23.
Development and validation of the air medical prehospital triage score for helicopter transport of trauma patients. Ann Surg 264(2):378-385, 2016.
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