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First, do no harm

Despite extensive research finding lights and siren use makes little difference in patient outcomes, and in fact causes harm to patients, providers and the public, too many continue to respond hot


According to data published by the National Highway Traffic Safety Administration (NHTSA), there are an average of 29 fatal crashes involving an ambulance, resulting in an average of 33 fatalities annually.

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The Hippocratic Oath, often pledged by aspiring physicians, includes the Latin phrase “primum non nocere,” generally meaning first, do no harm. One translation of the Hippocratic Oath includes the following phrase:

“I will follow that system of regimen which, according to my ability and judgment, I consider for the benefit of my patients, and abstain from whatever is deleterious and mischievous.”

This should be the goal of EMS leaders for our patients and our providers.

Thanks to the growing body of EMS research, and the Prehospital Guidelines Consortium, medical directors are increasingly using evidence to guide clinical protocols to achieve the goal of primum non nocere. Through this process, EMS clinical leaders objectively evaluate studies to judge the efficacy of the protocols they implement for the EMS system(s) for which they provide clinical oversight.

What if the evidence of a current practice used by EMS providers has been extensively researched, and determined to be detrimental to patients? Would the EMS agency leaders and medical director eliminate the protocol? Consider notable clinical practices like MAST trousers and EGTAs. These procedures have been removed from virtually all EMS protocols. Why? Because they 1., lacked clinical evidence that they made a difference in patient outcomes, and 2., potentially caused harm.

There is a current practice in use by too many EMS agencies despite tomes of research noting the practice makes little to no difference in patient outcomes, and in fact, causes harm to patients, EMS providers, and even the public; hot (lights and siren) vehicle operation.

The 2020 EMS Trend Report, produced by EMS1 and Fitch & Associates, included a question on hot responses: “Do you respond to 911 calls using lights and sirens?”

Eighteen percent of respondents indicated that they respond to every 911 call hot. The highest prevalence was in fire agency respondents (25%) and the lowest was reported by private, for-profit organizations with only 13%.

On a positive note, 28% of private, for-profit agencies and 26% of public, third service agencies indicated in the survey that they rarely use lights and sirens and only respond hot to time-critical calls.


Graphic/The 2020 EMS Trend Report

The hazards of hot responses are irrefutable. In 2018, 168 people died in crashes involving emergency vehicles. The majority of these deaths were occupants of non-emergency vehicles (56%); deaths among pedestrians, emergency vehicle drivers, and emergency vehicle passengers each accounted for about 13% to 14% of the deaths.

According to data published by the National Highway Traffic Safety Administration (NHTSA), there are an average of 29 fatal crashes involving an ambulance, resulting in an average of 33 fatalities annually. Although one-fourth of the fatalities are people inside the ambulance at the time of the crash, the driver or passenger of another vehicle is the one who is killed.

The same data estimates that an average of 1,500 ambulance crashes per year result in injury, with 46% of injuries occurring among people inside the ambulance at the time of the collision. That means the majority (54%) of people injured in ambulance crashes are citizens not part of the response.

Primum non nocere!

Why do some agencies continue a practice that makes little to no difference in patient outcomes, but places patients, providers and the public at risk for injury or death? Let’s dispel some commonly held misbeliefs, using published study data.

Myth #1: Hot responses save time

Let’s have an uncomfortable conversation about response times. Numerous studies have been published that debunk the belief that response time has any impact on patient outcomes for the vast majority of EMS responses. Moreover, for the limited types of calls in which time may matter (e.g. cardiac arrest, severe airway compromise), response times only make a difference if they are under five minutes. Let’s face it, the only way to even hope to achieve an EMS response time of under five minutes would be to deploy first response resources strategically in the community, no more than a mile or two between them, with vehicles running and personnel in the front seats ready to shift from park to drive. Oh, and of course we’d need to have the same PSAP which answers the call dispatch the unit (no time sucking phone transfers to a secondary PSAP or dispatch center).

A review of seven studies that have been published about the actual time savings of hot responses found the average times savings between hot and cold (non-light and siren responses) was two minutes, 30 seconds. Perhaps not worth the risks of the hot response (more on that later). If we are not willing to make the necessary changes to ensure a response time under five minutes as described above, then why should we be willing to place our providers and the public at risk for a two and a half minute response time difference?

Primum non nocere!

Myth #2: The public expects us to respond hot

Who is responsible for creating that expectation? We are! (OK, maybe Hollywood too?). The same could be said for the response time issue. It is our responsibility to change these expectations using the evidence about hot responses and response times in general. A public perception survey seems to reveal that the public would prefer “quite confidence” than the “bravado” of a hot response. In 1988, E. Marie Wilson led a survey of the public regarding attitudes toward EMS in Connecticut. Telephone interviews were conducted with 604 individuals across Connecticut. The top two reasons interviewees gave for being uncomfortable calling EMS was the sirens/noise, and getting a lot of attention. Is our bravado (hot response) keeping people from calling 911?

Primum non nocere!

The path to a safer EMS response

Every EMS system generates data. Data yields evidence. At MedStar, the Office of the Medical Director, our field operations and 911 communications leadership analyze clinical and operations data to make evidence-based decisions regarding appropriate response modes. Medical Priority Dispatch System (MPDS) response determinants and clinical intervention data are periodically analyzed to revise response priorities based on which determinants have a high or low propensity for critical ALS interventions. Priority 1 and Priority 2 determinants receive a hot response, with Priority 3 determinants receiving a cold response (and generally no requirement for first responders). This is a bit of work, but it results in a logical, locally evidence-based approach to determining appropriate response mode that saves lives, and helps ensure the safety of our personnel, and the public.


Dr. Doug Kupas, noted EMS physician (and 2020 NAEMT/NREMT Rocco V. Morando award winner), led a NHTSA commissioned project on the issue of HOT responses. Dr. Kupas’ report contains a treasure trove of information and recommendations regarding red lights and siren operations in EMS.

The recommendations include:

  • EMS agencies establish a protocol to reduce lights and siren response as much as safely possible.
    • A recommended benchmark in response to 911 calls would be to reduce the use of lights and siren by 50% for all 911 calls.
  • EMS agencies should consider target lights and siren transport at a rate of less than 5%.
    • The small amount of time saved will most likely be of clinical value in a small percentage of medical conditions.
  • As part of the agency’s quality improvement/performance improvement activity, EMS agencies should regularly measure their percentage of lights and siren use during 911 scene response and patient transport.
    • Where appropriate, individual case reviews for compliance with policy/protocols and appropriate use of lights and siren should be performed as part of regular QI audits.
    • Consider lights and siren transport as a parameter for mandatory QI case review (similar to cricothyrotomy, chest needle decompression or endotracheal intubation).

This comprehensive report is a must read for EMS agencies and can be accessed here.

Hopefully, EMS clinical and operational leaders will begin using some of these studies to implement evidence-based protocols limiting the practice of Hot responses and transports to the absolute minimum. Doing so may help prevent injury and death to the EMS workforce, and make our communities safer.

Who knows, maybe the 2021 EMS1 Trend report will reveal that even fewer EMS agencies are responding to all calls hot? Hope springs eternal!

Primum non nocere

Additional resources on safe 911 response

Learn more about lights and siren hot response with these resources:

Matt Zavadsky, MS-HSA, EMT, is the chief transformation officer at MedStar Mobile Healthcare, the exclusive emergency and non-emergency Public Utility Model EMS system for Fort Worth and 14 other cities in North Texas that provides service to 436 square miles and more than 1 million residents and responds to over 170,000 calls a year with a fleet of 65 ambulances. MedStar is a high-performance, high-value Emergency Medical Services system, providing advanced clinical care with high economic efficiency.

MedStar is one of the most well-known EMS agencies in the county, and operates a high-performance system with no tax subsidy, and the recipient of the EMS World/NAEMT Paid EMS system of the Year, and the only agency to be named an EMS10 Innovator by JEMS Magazine.

He is also the co-author of the book “Mobile Integrated Healthcare – Approach to Implementation” published by Jones and Bartlett Publishing.

He has 42 years’ experience in EMS and holds a master’s degree in Health Service Administration with a Graduate Certificate in Health Care Data Management. Matt is a frequent speaker at national conferences and has done consulting in numerous EMS issues, specializing in high-performance EMS operations, finance, mobile integrated healthcare, public/media relations, public policy, transformative economic strategies, and EMS research.

Matt is also immediate past president of the National Association of EMTs, and chairs their EMS Economics Committee.