Do we really need Lights and Sirens when transporting a patient?

For who has a multiyear experience in prehospital emergency medicine and deals everyday with emergency transportation of critical patients the sensation is that the use of emergency warning systems are, mostly of times, useless and doesn’t really have any impact on clinical outcomes. 

But beyond any subjective thought, do we have any evidence on that?

My analysis starts from this article published in 2018 on Annals of Emergency Medicine

by Brooke L. Watanabe, MD et al. and entitled  “Is Use of Warning Lights and Sirens Associated With Increased Risk of Ambulance Crashes? A Contemporary Analysis Using National EMS Information System (NEMSIS) Data”. The authors conclusion says that “Ambulance use of lights and sirens is associated with increased risk of ambulance crashes. The association is greatest during the transport phase. EMS providers should weigh these risks against any potential time savings associated with lights and sirens use.“

Curbside to Beside blog published an interesting post about this topic and resumed the data in this incredibly intuitive infographic

Data extrapolated from
Wantabe et al. (2018)

While ambulances crash rate when using L&S (light and sirens) in the response phase is slightly increased  (7.0 vs 5.4) in the transportation phase the amount of crashes associated with L&S use is significatively higher (17.1 vs 7.0). 

So L&S transportation increases the odd of crash (and this is intuitive) but, on the other side, is there any evidence that use of L&S increases response time and improve clinical outcome?

Fast is Time????

Fabrice Dami et al in an article entitled “Use of lights and siren: is there room for improvement?” found that the time saved with L&S transport was 1.75 min (105 s; P<0.001) in day time and 0.17 min (10.2 s; P=0.27) night-time.

So evidently fast is time, but is a gain of less than 2 min a clinical significative time?

Time is Life???

In 2010 in the article “Emergency Medical Services Intervals and Survival in Trauma:Assessment of the “Golden Hour” in a North AmericanProspective Cohort” concluded that “there was no association between EMS intervals and mortality among injured patients with physiologic abnormality in the field”.

Anderson et al in a 2014 article “Preventable deaths following emergency medical dispatch – an audit study” demonstrated how just 0,2% of the 94.488 “non L&S” dispatched emergencies died in the first 24 hours from the call.  Of those just 0.02% of total “non L&S” emergencies were considered “potentially preventable if the dispatcher had assessed the call as more urgent and this had led to an ambulance dispatch with a shorter response time and possible rendezvous with a physician-staffed mobile emergency care unit”

So mostly of the emergencies are not time sensitive and the clinical outcome does not differ if the transport time is shorter.

Take home messages for our system and for clinical practice

Maybe we need lights and sirens in response phase, cause slightly increase in accident risk corresponds to  some gain in arriving time on the scene.

Maybe we don’t need lights and sirens in transportation phase  cause a great increase in risk of crash do not correspond to a clinical sensitive time gain.

For sure when using L&S we need to be aware that the risk doesn’t worth the price, and even if we use L&S in the varies phases of emergencies pushing the threshold of                security too forward increases the risks and don’t improve clinical benefits for the transported patients.

Clinicians need to be more concerned about performing the right procedures to stabilise patients on pre-hospital phase more than hurrying  with unstable patients toward an unreal Eldorado and risking their own and patients lives.