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Wednesday, August 1, 2012

EMS EKGs Don't Increase Onscene, Transport Time

 Scene times & bumpersticker philosophy
To the guy who came up with the phrase "Golden Hour;" thanks for nuthin'.
"There is a golden hour between life and death. If you are critically injured you have less than 60 minutes to survive. You might not die right then; it may be three days or two weeks later -- but something has happened in your body that is irreparable."    Attributed to Dr. Adam Cowley  Reference
Catchy phrases always seem to win out over nuanced discussion, and we are left in the position of having to justify any increment in pre-hospital time intervals. Given the very real dangers of traveling lights & sirens, we instead should have to justify speeding, running red lights, and other ways of "expediting" transport.

"I wonder if it was worth it to encourage all that risky driving..." Not attributed to Dr. Adam Cowley
Nonetheless, there are medical situations where rapid transport is indicated, and most people agree that a STEMI is one of them. And although prehospital ECG acquisition has been shown improve various outcomes, some people may still harbor the concern that taking the time to do the ECG is delaying definitive treatment.

The study
With that in mind, a study of prehospital time intervals was recently published by the folks out in San Diego. The authors of Pre-Hospital Electrocardiography by Emergency Medical Personnel: Effects on Scene and Transport Times for Chest Pain and ST-Segment Elevation Myocardial Infarction Patients. studied scene time and transport time for patients with chest pain. They used a before & after design to look at the differences in times after EMS implemented prehospital ECG acquistion.

They found a statistically significant increase in scene time and transport time after they started doing ECGs. The increases in times, however, were trivial,  accounting for an additional 14 and 12 seconds, respectively. It just goes to show that, if you have over 20,000 subjects in a study, you are going to find statistical differences that just don't matter.

Interestingly, if they only looked at the subset of patients whose Marquette interpretation was *** ACUTE MI ***, they found that those same time intervals decreased, such that the total scene-to-hospital time was almost 3 minutes faster than in the pre-ECG days. So, it appears that, if anything, EMS care is speeding up the care of the specific patient population in question. In particular, the transport time was almost a minute faster, leading the authors to comment: 
"It is possible that once identified, obvious and suspected STEMI patients were treated with greater urgency resulting in expedited transport to the closest STEMI center."
A note of caution
 While the paramedics likely treated the identified STEMI patients with "greater urgency," as the authors suggest, I am paradoxically concerned about such a large drop in transport time. How was this achieved? The study wasn't designed to answer that question, but another recent study suggests it was unlikely to be because a bunch of new cath labs were built in the area.

Instead, I am concerned that the dramatic reading of *** ACUTE MI *** prompted the drivers of the ambulances to "expedite" transport by driving warp factor 10. The problem is that, when the view through the windshield looks like this:

Pictured: about to bounce too close to a supernova.
... the next view could be something like this:

Aaaannnd, supernova. *
Let's be careful out there. Just getting the ECG is probably saving lives - don't risk them during transport, "golden hour" or not.
*Reference. Note that picture this is used for illustration, but the EMS crew apparently was neither responding nor transporting, and a car ran into them.


5 comments:

  1. I think some of that time difference is attributable to provider behavior post-nasty 12-Lead. I know I personally go right to placing the patient on the stretcher and moving to the truck. Calling the receiving facility while my partner or the firefighters are buckling in the patient. No waiting to start a line and draw labs on scene, etc.

    Otherwise, if its not a concerning 12-Lead, we may sit in the house and gather more information and medications. If the patient has bad looking veins, we'll stay and play for a bit to get a line.

    Pulling our times, average for all Provider Impression = "Chest pain / discomfort" transports (01Aug2011-01Aug2012, n=147) is 38 minutes On Scene -> At Receiving (min=19,max=71).

    Average for all Destination Basis = "STEMI" or Hospital Notify = "STEMI" transports (same time, n=12) is 29 minutes On Scene -> At Receiving (min=19,max=56), 12 minutes Depart Scene -> At Receiving (min=10,max=15).

    Average for all Mode to Receiving = "Lights and Sirens" or "Upgraded" (same time, n=195) is 14 minutes Depart Scene -> At Receiving (min=4,max=29). Total mileage is usually 8-10 miles, utilizing a highway for half of it.

    At least in our service, some of it could be "excessive driving", but realistically it looks like most of our savings are on scene times.

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    1. Average for all transports (same time, n=1127), 36 minutes On Scene -> At Receiving (min=7,max=160), 17 minutes Depart Scene -> At Receiving (min=4,max=63).

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  2. If I understand your stats, your suspected STEMI patients have a transport time interval that is 2 minutes shorter than all other lights & siren transports, but the onscene interval is about 9 minutes shorter.

    Your experience is reflected in this study, since the STEMI patients had onscene times about 2 minutes shorter than the "historical" chest pain patients.

    However, they also had shorter transport times. Given that it's difficult to show that lights & siren mode significantly affects response/transport time, I figure they had be hauling arse to show that kind of drop in time.

    Anyway, I hope that my theorizing does not detract from the main point - "it delays transport" is not an acceptable reason to forgo a 12-lead!

    ReplyDelete
    Replies
    1. The 2 minutes may not have significance due to the small numbers, but on one point the data agrees: it does not delay transport!

      It seems odd that there would be a speed increase, as every L&S feels like "warp speed"! We're driving too fast in general, data or not. :-(

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  3. When we first started doing 12 Leads, a number of us, which included me, felt that there would be an inordinate increase in on scene times. While that might have been try at first, with time we got faster at placing the chest leads. Now, we don't even think about the increase in time, if there even is one. The benefits of an earlier 12 Lead far outweigh any time increase.

    ReplyDelete