Studies Examine Effects of Scene Times for STEMI Patients

Historical controls: A review of previous data that gives a baseline of information prior to new study interventions.

For this month’s cardiac-focused issue, two studies bring to light the ever-important issue of scene times. A 90-minute door-to-balloon time has become an industry standard for in-hospital care of ST-elevation myocardial infarction (STEMI) patients. But prehospital time isn’t often a reported factor in STEMI outcome research

10 Minutes for On-Scene STEMI care?
Haroon C, Ratner D, Pozo M, et al. Prehospital delay and its impact on time to treatment in ST-elevation myocardial infarction. Am J Emerg Med. 2011;29(4):396—400.

This study examines “total time” for STEMI patients, from symptom onset to balloon inflation in a cardiac catheterization lab. The setting of this small, 60-patient study is a single urban system in New Jersey in which average time intervals were the following: a response time of 10 minutes, on-scene time of 18 minutes, transport time of 11 minutes and door-to-balloon-time of 109 minutes. The group reviewed charts just for confirmed STEMIs that received percutaneous coronary interventions (PCIs).

The authors conclude that the biggest time interval in their EMS system is scene time, so they advocate for a reduction of on-scene time to achieve an ideal prehospital time of less than 30 minutes and ideal total time of less than 120 minutes.

Patients with total time greater than 120 minutes had significant complications and increased mortality rates. With scene times of 18 minutes, and more importantly a plus or minus margin of nine minutes recorded in this study, I’d recommend looking at reducing time intervals in these categories: response, scene and especially in-hospital time. So let’s all try to work a little faster.

As part of my continuous quest for awareness on the best ways to decrease EMS non-transports in high-risk patients, I found one statistic in this study astounding–a 20% self-transport rate. The authors don’t explain this statistic, which leaves me wondering: Did 20% of their STEMI patients actually adamantly refuse transport? Was EMS aware they were having a STEMI at the time the self-transport decision was made?

Consistent Scene Times
Werman H, Newland R, Cotton B, et al. Transmission of 12-lead electrocardiographic tracings by emergency medical technician-basics and emergency medical technician—intermediates: A feasibility study. Am J Emerg Med. 2011;29(4):437—440.

This second STEMI study is particularly interesting in comparison with the first one. The authors clearly demonstrate that EMTs in a rural Ohio EMS system can accurately obtain and transmit diagnostic quality 12-lead ECGs in 95.5% of cases. There’s no big news here because this has been demonstrated many times before. These authors’ reported scene times for these BLS crews remained constant at 19 minutes plus or minus 12—14 minutes during the study period (compared to historical controls).

I found it interesting that rural BLS crews in Ohio had similar scene times to ALS crews in the New Jersey study. If scene time is the major factor being considered, is it time for urban systems to add more–and cheaper to operate–BLS ambulances that can drop response times and transmit 12 leads?

I hope some budding EMS researchers will be concerned about this issue and direct their energy into productive prehospital research to prove that a paramedic patch–and more appropriately, a provider’s assessment and treatment skills–really do make a difference. It’s time we use science to make our points, not rhetoric.

Watch Box
Arendts G, Sim M, Johnston S, et al. ParaMED Home: A protocol for a randomized-controlled trial of paramedic assessment and referral to access medical care at home. BMC Emerg Med. 2011;11(1):7.

Stay tuned for results from an ongoing Australian project regarding non-transport of low-acuity 9-1-1 patients. This prospective, randomized and outcome-based study shows great promise. Paramedics with a small amount of extra training are selecting patients who can receive a home visit from a nurse practitioner instead of taking the trip to the emergency department.

Also, many great EMS-related abstracts appeared in the Society for Academic Emergency Medicine (SAEM) scientific assembly in June. Some noteworthy abstracts include a study on blow-by oxygen by EMS researcher and author Lawrence Brown.

Another study of interest is the predictive value of “EMS Provider Judgment” in recognizing the acuity of trauma patients. This study showed Denver and Seattle EMS crews have great instincts identifying high-risk trauma patients that standard triage criteria can miss.

This article originally appeared in August 2011 JEMS as “Time on Our Side? Decreased scene times and STEMI survival.”

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