Search Terms: Advanced life support, basic life support, emergency medical services (EMS), emergency medical vehicle collisions (EMVCs), outcome, patient transport, protocols, warning lights and siren (L&S), emergency transportation, Douglas Kupas, David Dula, Bruno Pino, 1994, Prehospital and Disaster Medicine, study, cause of liability, medical protocols, safety concerns, prehospital and disaster medicine, 1994, ambulance accidents, patient outcome, limit lights and siren transport, lights and siren, transport, emergency medical transport, outcome studies,

Prehospital and Disaster Medicine, October-December 1994, Vol. 9, No.4

Douglas F. Kupas, M.D., David J. Dula, M.D., FACEP, Bruno J. Pino

Patient Outcome Using Medical Protocol to Limit "Lights and Siren" Transport


Safety concerns have prompted an increasing interest in emergency medical vehicle collisions (EMVCs). A 48-month study of ambulance accidents in New York revealed 1,412 reportable accidents with six fatalities and 1,894 injuries (1). Clawson (2) estimates that up to 12,000 EMVCs annually in the United States and Canada are associated with the use of warning "lights and siren" (L&S). Additionally, when an EMVC occurs using L&S, it is more likely to yield injuries (3). Emergency medical vehicle collisions are the leading cause of liability actions to emergency medical services (EMS) systems and providers, and in some cases, EMVC claims are 23 times more common than are medical liability claims. (Personal communication, Steven A. Forry, EMS Specialist, Glatfelter Insurance Group, January 1994) Considering these risks, emergency vehicle drivers must have reasonable grounds for the use of L&S (4). Many authorities believe that less than 5% of all ambulance calls medically require L&S transport (5). Despite these reasons to avoid the routine use of warning L&S during patient transport, the practice remains common.

Analysis of a Pennsylvania EMS trip sheet data indicated that 58% of all emergency calls in 1991, culminated in emergency transport. The Pennsylvania EMS Act prohibits the use of L&S to transport patients without life-threatening problems; however, 16% of the patients transported emergently were listed as having minor severity and only 19% were believed to be life-threatening . (Personal communication, Office of K. Hum, Ph.D., Division of Emergency Medical Services, Pennsylvania Department of Health, January 1993).

In this study using a protocol to direct the use of warning L&S, the outcome of patients transported when ambulances were not using L&S is reported.


The study was done in cooperation with a county-wide, single-provider, private EMS system. This system uses 11 advanced life support (ALS) ambulances with crews comprised of one paramedic and one emergency medical technician (EMT) to service a call volume of 14,000 calls for a population of 90,000. The setting is a rural/suburban county in Pennsylvania. During the four-month study period, all EMS calls that originated as an emergency request for service and culminated in ground transport to an emergency department (ED), were included. A protocol , based on specific medical criteria, was developed, and this protocol was carried in each ambulance (Table 1). The protocol was implemented at the time of the study; however, it was based on the previously existing routine practice of providers within the system.

The patientās condition immediately before transport, after the usual basic life support (BLS) or ALS treatment on-scene, determined mode of transport. The protocol directed EMS providers to transport patients emergently (using L&S) if they met any of the criteria. Otherwise patients were transported in vehicles using headlights, but without L&S. Data sheets were completed by a member of the crew immediately following the conclusion of each trip.

The information recorded included the patient's condition during transport, mode of transport, type of symptom, reason for L&S transport if applicable, and destination. Patient condition , as evaluated by EMS providers, was reported as "improved," "unchanged/stable," "unchanged/unstable," "worsened," or "expired." If multiple patients were transported by the same ambulance, one data sheet was submitted for the most seriously ill patient, as determined by the EMS provider. Data sheets were collected by station managers and assessed for completeness. The authors reviewed trip sheets on every patient transported emergently or recorded as worsened, unstable/unchanged, or expired. Paramedics were interviewed when additional information was needed, and the directors of all receiving emergency departments (EDs) reviewed the hospital records of all patients who were transported without L&S, and had recorded worsening medical condition. Differences between groups were determined using Chi-square analysis with statistical significance set at 0.05. The project was approved by the Institutional Research Review Board, and the regional and local EMS directors.


A total of 1,625 patients were entered into the study. Using the protocol, only 130 patients (8%) were transported to the hospital using L&S. Most patients (92%) evaluated using the protocol, were transported nonemergently, without the use of L&S. Changes in the patient condition that occurred during transport, based on the evaluation by their EMS providers, are summarized in Table 2.

The symptoms elicited from those patients conveyed in a non-L&S mode as groups included: 1) chest pain or cardiac problems (14.2%); 2) shortness of breath or respiratory complaint (10.6%); 3) trauma (17.8%), abdominal pain or gastrointestinal complaint (6.9%); and 4) other (50.4%). In the non-L&S-transported group, 47% (697 of 1,495) of the patients had received at least one ALS intervention including pharmacologic therapy and /or an ALS procedure. A summary of the condition of all patients conveyed without L&S that were reported to have worsened en route to the hospital is provided in Table 3.

One patient with a pacemaker who was transported non-L&S, abruptly developed a tachycardia that initially was thought to be a "runaway pacemaker". Although a runaway pacemaker could not be treated definitively by the EMS personnel, the patient was hemodynamically stable on arrival in the ED, and the patient had no morbidity related to the event. Later the rhythm was determined to be a supraventicular tachycardia with a normally functioning pacemaker.

All other non-L&S-transported patients who were reported to have worsened during transport had changes that were treated adequately with BLS-or-ALS-level care. All patients who reportedly worsened and required ALS interventions had intravenous access established previously.

When comparing changes in patient conditions between the two modes, 24 of the 130 (18%) patients transported L&S worsened or expired during conveyance; whereas, only 13 of 1,495 (1%) of the nonemergently transported patients worsened en route to the hospital (p<0.001).

Of the patients transported with L&S, the following protocol criteria (Table 1) were used most commonly to justify L&S transport; vital signs (38%); respiratory (13%); cardiovascular (19%); and neurologic (20%).

The last medical criterion in the protocol allows for emergent transport of any patient the provider believes may worsen by a delay equivalent to the time that could be gained by L&S transport. This general criterion was used in 41 of 130 (32%) of the L&S transports. Nineteen of these were caused by trauma triage criteria for mechanism of injury. The remaining 23 (18%) were emergencies not covered by the other criteria. Four cases had systolic blood pressures <90mmHg or Glasgow Coma Scale scores of <13mmHg, that did not meet the vital sign criteria of the protocol. Other reasons for the use of L&S transport included chest pain with associated nonprotocol problems such as bradycardia, tachydysrhythmia, or severe pain (8), rapid transport ordered by physician (2), severe abdominal pain (2), prolonged hypothermia (1), suspected pacemaker malfunction (1), unstable angina insisting on transport to tertiary-care center 46 miles away (1), and congested traffic at a football game (1).

Receiving physician opinion was available immediately after the call in 982 cases; and when available, there were no cases of potential worsened outcome caused by non-L&S- transport. Physicians at the receiving facility reviewed every non-L&S case that was reported to have worsened en route, ant the physicians did not believe that any of these patients arrived in extremis.

The mean transport time was 18 minutes for all transports, and there were no EMVCs during the study period.


In this study, the application of this protocol resulted in transport without L&S for 92% of patients. Nearly one-half of these non-L&S patients transported received ALS interventions, and many had serious complaints such as chest pain, or shortness of breath. In patients whose condition reportedly worsened during transport, neither trip sheet information nor paramedic interviews revealed any morbidity related directly to the changes in patient's condition while en route to the hospital in the non-L&S group. In patients whose condition reportedly worsened during transport, physicians at the receiving hospital did not believe that any of these patients arrived in extremis or required any immediate emergency interventions.

There are several limitations to the interpretation of these results. The last medical criterion in the protocol allows for L&S transport of any patient the provider feels may worsen by delay equivalent to the anticipated time that could be gained by L&S transport. This basic idea is the foundation of the study, and this statement could stand as the sole criterion. Yet, the intention was to provide personnel with a protocol that would allow for maximal use of objective information. This general criterion was used to justify L&S transport in nearly one-third of the cases transported emergently. Mechanism of injury in trauma patients was the most common reason for using this criterion. Although assessing the mechanism of injury is important in triaging trauma patients to appropriate emergency facilities, it may not predict severe injury when the patient does not meet the vital signs or anatomic injury trauma triage criteria of the American College of Surgeons (6). Paramedic training emphasizes the importance of the mechanism of injury, and paramedics tended to use severe mechanisms as justification for L&S transport, even when the patient was considered stable.

Another study of limitation was the review of patients based on the EMS providers' subjective evaluation of patient condition during transport. Although they were asked to report any objective or subjective changes in the patient's condition, this study does not preclude possible discrepancies between the providerās opinion and the receiving physician's evaluation.

This EMS system uses ALS staffed and equipped units universally. Lesser levels of staffing may affect the provider's confidence in patient assessments and may limit their ability to treat problems that arise during transport.

As with all clinical protocols, it is important to validate these results in other EMS systems. This protocol was associated with non-L&S transport 92% of the patients in this study. The small number of patients transported with L&S may be reduced further by improving the subjective criteria in the protocol. An ideal clinical protocol is entirely objective, but it is difficult to include only objective criteria in a protocol that is applicable to every patient transported by an EMS system, while ensuring minimal adverse outcomes. The subjective portions of this protocol may be reduced as additional studies become available.

Emergency medical services systems function to provide out-of-hospital medical care, but the safety of the EMS crew and the general public is paramount to these operations. Before the development of modern EMS systems, out-of-hospital care was based on rapid transport to a hospital. This was accomplished by the almost universal use of L&S. As EMS matures, the ideas that are rooted in tradition have been challenged to prove their benefit relative to their associated risks. The use of L&S also must conform to this risk versus benefit scrutiny. Emergency medical vehicle collisions have an impact on EMS liability, public safety, public opinion, and patient care, and medical directors have taken and increased interest in the use of L&S as shown by a recently published position paper by the National Association of EMS Physicians (7).

Protocols provide guidance to EMS for making decisions regarding the use of L&S. Medical outcomes should guide the use of these devices; by adopting protocols for L&S use, medical directors have a standard by which to audit the appropriate use of L&S.


This medical protocol directing the use of warning L&S during patient transport results in infrequent L&S transport. In this study, no adverse outcomes were identified as related to non-L&S transports.


  1. Elling R: Dispelling myths on ambulance accidents. JEMS 1989; 14:60-64.
  2. Clawson JJ: Running "hot" and the case of Sharron Rose. JEMS 1991; 16:11-13.
  3. Auerbach PS, Morris JA, Phillips JB Jr., et al: An analysis of ambulance accidents in Tennessee. JAMA 1987; 258:1487-1490.
  4. George JE, Quattrone MS: Above all do no harm. Emerg. Med. Tech. Legal Bull. 1991; 15:4.
  5. Leonard WH: EMS system failure. The Gold Cross 1991; 11-13.
  6. Bickell WH, Sacra JC, Thompson CT: Prospective evaluation of field trauma triage. Ann Emerg Med 1993; 22:919. Abstract.


Table 1- Medical criteria for emergent lights and siren transport

  1. Vital signs (patients >8 years old)
    1. Systolic BP <90 mmHg with possibly related disease or trauma
    2. Respiratory rate >36/min with patient as relaxed as possible
    3. Respiratory rate <10/min
  1. Airway
    1. Inability to establish or maintain a patent airway
    2. Upper airway stridor
  1. Respiratory
    1. Severe respiratory distress unresponsive to BLS/ALS treatment

4. Cardiovascular

    1. Cardiac arrest
    2. Severe, uncontrolled hemorrhage of any cause
  1. Trauma
    1. Penetrating wound to head, chest, or abdomen except for obviously superficial wounds
    2. Two or more suspected proximal long-bone fractures
    3. Major amputation including two fingers, three toes, or above wrist or ankle
    4. Penetrating or blunt neck trauma except obviously mild or superficial injury
    5. Neurovascular compromise of an extremity
  1. Neurologic
    1. Glasgow Coma Scale score <13, only if acute change of any cause
    2. Seizure activity not controlled by BLS/ALS treatment
  1. Obstetric
    1. Intrapartum emergencies including, but not limited to, cord prolapse, premature labor, and arrested delivery
  1. Pediatric
    1. Upper airway stridor
    2. All patients <8 years of age individually based on the mechanism of injury, degree of distress, and the EMS personnelās experience with patients of this age; when in doubt, seek advice from medical command and/or transport emergently
  1. Other

a. Emergent transport should be used in any situation which the most highly trained EMS provider believes that the patient's condition could be worsened by delay equivalent to the time that could be gained by emergent transport. In all cases using this option, documentation of the reason for this on the trip must be recorded.

Table 2-Changes in patient condition during transport by ambulances (n-1,625)

L&S Non-L&S

n (%) n(%)

Expired 17 (13) 0 (0)

Worsened 7 (5) 13 (1)

Unchanged 84 (65) 1,324 (91)

Improved 22 (17) 124 (8)

Total 130 (8) 1,495 (92)


Table 3-Case summaries of patients whose conditions were reported to have worsened during transport (ED=Emergency department)

  1. 56 year-old coughed small amount of blood after choking episode.
  2. 63 year-old with seizure en route, adequately treated with diazepam.
  3. 47 year-old with overdose and episode of decreased level of consciousness en route.
  4. 82 year-old initially complained of nausea and vomited, became unresponsive as stroke progressed.
  5. 23 year-old with seizure en route, adequately treated with diazepam.
  6. 93 year-old initially complained of chest pain, developed paced, tachycardiac rhythm thought to be a runaway pacemaker rhythm.
  7. 35 year-old postictal, with increase in confusion.
  8. 70 year-old with chest pain, became hypotensive en route (systolic blood pressure = 80mmHg).
  9. 67 year-old became hypotensive after nitroglycerin, adequately treated with intravenous fluids.
  10. 18 month-old with minor head injury and decreasing responsiveness en route, alert on arrival at ED.
  11. 38 year-old fell from tree, episode of decrease in blood pressure.
  12. 88 year-old fell striking head, hypotensive episode en route.
  13. 42 year-old with anaphylaxis resulting from bee sting, improved with epinephrine then wheezing recurred en route.