Sharron Rose Frieburg was 18 years old when a Bloomington Fire Department ambulance ran a red light and struck the vehicle in which she was traveling. She sustained permanent injuries including cognitive impairment and hemiparesis and has persistent difficulty ambulating and speaking.¹ Bloomington, Illinois, paid out nearly $5 million to care for Sharon’s lifetime of medical needs. The ambulance was transporting a patient with an ankle injury to the hospital.

Potential Benefit Versus Risk

A medical therapy has associated risks and benefits and the likelihood of each should be weighed with every single administration. That evaluation starts in the field when your local EMS agency is responding to a scene. Just like any other medical management, ambulance lights and sirens (L&S) during response to the scene and transport to the hospital should be considered a medical therapy and prescribed for the patient population with a potential for benefit. Clearly, there are conditions that would benefit from L&S medical therapy in which the potential benefits outweigh the risk of harm. However, in order to improve EMS and public safety, as well as enhance the delivery of patient care, it is important to judiciously evaluate the risks and benefits of all aspects of prehospital care, including L&S. The current status quo that an EMS agency responds to the scene greater than 50 percent of its call volume with L&S or transports patients with L&S greater than 25 percent of the time should not be permitted any longer.

The clinical utility of L&S has been questioned since 1953, when studies revealed that 88 percent of patients arriving by ambulance did not require time sensitive medical management.² A 1994 study found that limiting L&S to 8 percent of transported patients did not increase the mortality rate. Furthermore, a 2014 study determined the number needed to treat with L&S to prevent one patient’s death is 5,000. With these findings, the safety, role, and proper utilization of L&S must be evaluated and reconsidered.²

The National Highway Traffic Safety Administration (NHTSA) estimates 4,500 ambulance crashes resulting in 33 deaths annually.³ About 25 percent of the fatalities are of the patients or EMS providers in the ambulance, with the remaining being pedestrian bystanders or other vehicle occupants. EMS providers die from transportation collisions at a greater rate (9.6 per 100,000) than police officers (6.1) or firefighters (5.7). Rear occupants are 2.7 times more likely to die in an ambulance crash, often due to lack of seatbelts. Research has shown that most of these collisions are attributed to human error and thus preventable.

Ambulances inherently raise the risk of collisions due to their increased mass requiring extra braking distance. Even when compared to vehicles of similar size, ambulance crashes occur more often at intersections, with 84 percent involving three or more people. Furthermore, the majority of EMS collisions occur when driving with L&S. A Denver study reported that L&S use accounted for 91 percent of all ambulance crashes.²

Obviously, the concern with unnecessary L&S use is the risk of injury to providers, patients, or pedestrians in a collision. However, there are other negative externalities as well. Studies suggest that L&S use increases patient stress and anxiety, which may result in increased catecholamine surge, heart rate, and blood pressure.^2,4 In urban regions, “alarm fatigue” is a concern when drivers don’t clear the way for ambulances because they are too frequently confronted with emergency vehicles driving with L&S. If the frequency of L&S use decreased, limited to cases with the potential for real benefit, perhaps alarm fatigue would diminish. Finally, there is the recognition that L&S travel is just not that effective.

The Effectiveness of Lights and Sirens

The major indication for L&S is a presumed significant decrease in response and transport time. However, multiple studies reveal minimal decrease in transit time with L&S use, with an average of 1.7 to 3.6 minutes saved.⁵ In Greenville, North Carolina, the average reduction with L&S was 43.5 seconds. In congested, urban regions, there is not a marked difference with L&S either. In one urban study, L&S use resulted in a three-minute reduction in Minneapolis. In Washington D.C., there were 3.6 and 3.0 minute faster mean response and transport times with L&S use, respectively. Studies also show that the majority of patients agreed with the practice of non-L&S transport once evaluated by EMS.²

For most conditions, EMS providers can provide timely care on-site or en route to diminish the importance of time saved by L&S transport, thus reducing the risk to providers, patients, and public. In greater than 90 percent of patients, there is no improved outcome from L&S use.² For some conditions, such as ST-elevation myocardial infarctions, trauma with life-threatening hemorrhage, obstetrical emergencies, or ischemic strokes, the use of L&S use may improve patient outcome by decreasing transit time. However accurate prehospital notifications to the receiving hospitals may be more beneficial than L&S as this should reduce in-hospital delays waiting for therapeutic interventions. In some cases, prehospital notification has shown an evidence-based improvement in patient outcome by mobilizing the necessary resources.^2,6

Additionally, the acoustic aspects of siren effectiveness have been studied in detail.² Source characteristics such as level, frequency, and directionality, and temporal propagation characteristics such as geometric spreading, atmospheric absorption, topography effects, and background noise are all important components. A 1978 study’s conclusion, reaffirmed in a 2012 study, found that siren warnings were only effective when vehicles were traveling in the same direction ahead of the emergency vehicle, when a vehicle was weaving through dense, stationary traffic, or to pedestrians.² It is clear that sirens may not be as effective as providers may assume and thus cannot be relied on to clear the way.

One retrospective study found that only 5 percent of patients benefit from the time saved by L&S.⁷ EMS medical directors should focus the training and preparation of EMS providers to provide appropriate medical interventions and to provide accurate and reliable prehospital notifications. Medical directors and operational supervisors for EMS agencies should conduct quality assurance initiatives to ensure a constant assessment of L&S utilization and its effects on patient outcomes.

Emergency Medical Dispatch Risk Stratification

Emergency medical dispatch (EMD) risk stratify 911 calls and initiate a non-L&S response based upon a structured call-taking process, a concept first pioneered by Dr. Jeff Clawson in 1982. In the same year that Salt Lake City instituted an EMD policy to risk stratify calls and identify time-dependent emergencies, they decreased the L&S response by 50 percent. The same year there was a 78 percent reduction in emergency vehicle collisions.^2,9

Variability of L&S Use Nationwide

The recognition of safety risks associated with L&S has initiated a change in EMS safety culture. Between 2010 and 2015, the rate of L&S use during patient transport decreased. However, the rate of L&S use when responding to the scene was constant. There is significant variability in the utilization of L&S throughout the country for both response and transport. For example, rural and urban areas are more likely to use L&S compared to suburban regions. Such variable utilization of L&S is likely influenced by EMS agency policies, municipal contracts, traditions within agencies, driver training, and medical oversight.²

It is unfortunately common for municipal contracts to require EMS response within eight minutes of dispatch with financial ramifications if the time requirement is not met. In 2015, the EMS agencies in Tulsa and Oklahoma City changed the response policy in order to reduce L&S use to 33 percent of its responses.² It shifted focus to patient outcomes and quality of care as more important metrics than response time. Importantly, after reduction in L&S rates, there was no associated increased morbidity or change in their cardiac arrest survival rate.² Additionally, Merlin and colleagues developed a simple medical protocol for L&S transport which reduced an urban EMS agency from 50 percent to 29 percent for patients transported by advanced life support providers.⁸

Each EMS agency should measure their percentage of L&S use of total 911 call volume and aim to reduce the percentage to the minimum effective rate. The goal for each EMS agency, after comparing national statistics and trends, should be less than 50 percent L&S use during response and less than 5 percent during transports.² Following these benchmarks would likely improve patient, provider, and public safety without increasing detrimental patient outcomes in most EMS agencies. Providing sound leadership, the ACEP EMS Committee has recommended that EMS medical directors should limit L&S use as much as possible. The role of L&S should be only to “request the right of way,” instead of continuous L&S use.

Opportunity for Improvement

Currently only 17 percent of EMS agencies use L&S for less than 50 percent of all calls; most EMS agencies use L&S for 80 percent of 911 calls.² Creating EMS and ambulance response guidelines for appropriate use of L&S, with a transport goal of less than 5 percent of 911 calls, should be a priority for EMS agencies and medical directors. L&S should only be utilized when the level of care needed is greater than what EMS providers can offer. As part of their quality improvement measures, EMS agencies should routinely monitor their percentage of L&S use and evaluate their protocols to try to minimize L&S use. Increased training on the hazards and standardized protocols regarding L&S use should be considered as mechanisms to improve EMS safety for providers, their patients, and the public.

References

1. Fraizer A. After the accident. J Emerg Dispatch. June 5, 2017. Available at https://iaedjournal.org/after-the-accident. Accessed March 19, 2018.
2. Kupas DF. Lights and siren use by emergency medical services (EMS): above all do no harm. S. Department of Transportation National Highway Traffic Safety Administration Office of Emergency Medical Services website. May 2017. Available at https://www.ems.gov/pdf/Lights_and_Sirens_Use_by_EMS_May_2017.pdf. Accessed March 19, 2018.
3. Smith N. A national perspective on ambulance crashes and safety. EMS World. 2015;44(9):91-94.
4. Witzel K. Effects of emergency ambulance transportation on heart rate, blood pressure, corticotrophin, and cortisol. Ann Emerg Med. 1999; 33(5):598-599.
5. Dami F, Pasquier M, Carron PN. Use of lights and siren: is there room for improvement? Eur J Emerg Med. 2014;21(1):52-56.
6. Patel MD, Rose KM, O’Brien EC, et al. Prehospital notification by emergency medical services reduces delays in stroke evaluation, findings from the North Carolina stroke care collaborative. Stroke. 2011;42(8):2263-2268.
7. O’Brien DJ, Price TG, Adams P. The effectiveness of lights and siren use during ambulance transport by paramedics. Prehosp Emerg Care. 1999;3(2):127-130.
8. Merlin MA, Baldino KT, Lehrfeld DP, et al. Use of a limited lights and siren protocol in the prehospital setting vs standard usage. Am J Emerg Med. 2012;30(4):519-525.
9. George JE, Quattrone MS. Above all—do no harm. Emerg Med Tech Legal Bull. 1991;15(4).

Dr. Bona is a second-year emergency medicine resident at Maimonides Medical Center.

Dr. Friedman is a board-certified EMS and emergency physician. He is the associate medical director of prehospital care at Maimonides Medical Center and the lead house physician at Yankee Stadium, Madison Square Garden, and the US Open. Dr. Friedman is the academic co-director of the Mass Gathering Medicine Summit. He serves as the medical director for numerous annual mass gatherings.