The True Cost of Ambulance Diversion


Studies show that EMS delivers a significant percentage of patients who will go on to be admitted. Armed with these numbers, we must rethink diversion, considering its true cost to the hospital.


Studies show that EMS delivers a significant percentage of patients who will go on to be admitted. Armed with these numbers, we must rethink diversion, considering its true cost to the hospital.

Hard data can tell us some essential things about the emergency department story, from resource utilization to management trends. In 2012, the ED Benchmarking Alliance gathering data from more than 1,000 participating hospitals, and the results were illuminating to say the least. This month we examine the data that reveals a significant correlation between ambulance transports and ED visits that lead to hospital admission.

Specifically, the EDBA survey asked member EDs to report the percentage of patients that arrive by EMS, and those that arrive by EMS and are admitted from the ED to the hospital. For the year 2012, about 16% of patients seen in the ED arrive by EMS, and more than 40% of those EMS patients are admitted (Table 1). This percentage has been very consistent over the last nine years. But there is significant variation between the ED volume cohorts. EMS arrival rates are higher in those EDs with larger volumes, and by far highest in EDs serving adults, where about 23% of their patients arrive in an ambulance. Those EDs over 40K volume see about 19% of their patients arrive by EMS, and there are a number of those EDs with EMS arrivals over 30%. Ambulance arrival rates hover around 12% in smaller volume EDs, and about 8% in EDs that serve a primarily pediatric patient population.

The percentage of patients arriving in an ambulance predicts the percentage of ED admissions to the hospital, as illustrated in Table 1.


Column one and column three of this table demonstrate a high level of correlation.

Available data indicate that population utilization of ambulances is around 100 times per 1000 persons in a service area. Utilization of EMS in communities, and the characteristics of EMS patients, are not widely reported. There is a terribly inaccurate myth that EMS patients are persons just looking for a free ride to the clinic, or for a quicker pathway to an ED bed. The most common symptoms resulting in an EMS transport are the following:

  • Chest symptoms, and those relating to Acute Coronary Syndrome (ACS) presentations
  • Shortness of breath
  • Injury requiring packaging of some type
  • Altered level of consciousness
  • Abdominal discomfort

How much Should the Hospital Spend to Avoid EMS Diversion?
In America’s current health care market, hospitals survive on revenue from inpatient service, and patients admitted through the ED are major contributors to that revenue stream. EMS transports many of those more critical patients to the hospital, where emergency physicians then make critical patient decisions about admission, transfer or outpatient care.

The cost of diversion, therefore, is very significant. To calculate the cost, one might count the average number of EMS patients arriving during the busy hours of the day (not including the middle of the night, when diversion rarely is utilized). Assume that arrival rate is a modest two EMS patients per hour. Count the average revenue for ED services for those patients for the hospital. Many hospitals use a direct revenue per patient of $500. Calculate the average rate of admission for arriving EMS patients. In the EDBA survey, it is 40%. Calculate the average contribution to overhead for a patient that is admitted. Many financial officers report that an admitted patient contributes $6000 above the direct cost of service. If that is the case, every 10 patients diverted costs the hospital 4 admissions, or $24,000. Calculating an economic loss for 10 patients then equals: $500 times 6 patients ($3000) plus $24,000 for admissions, totaling $27,000, or $2700 per patient. So the cost of an hour of diversion for an ED that greets two EMS patients per diversion hour is $5400. This is direct revenue loss only, not the loss of the patient for future visits and admissions, and loss of relationship with EMS.

One could speculate that ED crowding and diversion are increasing the acuity of EMS patients. The diversion process causes some EMS providers to advise lower acuity patients to go to the ED by private vehicle, so they can select the hospital of their choice. The remaining EMS patients would be more likely to have high acuity needs, and require hospital admission. It is also notable that communities having extensive networks of urgent care centers have EMS patients that are more likely to be admitted.

Emergency Medical Services are a valued partner to hospitals and their emergency departments. EMS patients are much more likely to need higher levels of ED service, and to be admitted to the hospital. Diversion of EMS due to ED crowding, which often results from boarding of admitted patients in the ED, is costly to the hospital, and causes long term damage to the relationship of the hospital with EMS providers and the community.

Dr. Augustine is the vice president of the Emergency Department Benchmarking Alliance and is the Director of Clinical Operations for Emergency Medicine Physicians (EMP) in Canton, Ohio.

Burt CW, McCaig LF, Valverde RH. Analysis of ambulance transports and diversions among U.S. emergency departments. Ann Emerg Med 2006;47:317–26.


  1. Ambulances have been occassionally diverted since they were pulled by horses.After my successful experience with occassional overload and diversion from Maryland Shock Trauma, I brought it to the vast NYCEMS world in 1981 ….basically to be used(as at MIEMSS) only when critical emergency care would otherwise suffer. Remember there were lots of nearby EDs.

    It didnt take long to recognize that a lack of monitoring capability in the ED(not in ICUs) and lack of available speciality inpatient beds(mainly psych, peds, burns and OB)were logical reasons to divert(avoiding immediate ambulance transfers)

    The issues for hospital administrators focused pretty much on money(in large part the payment class of patients and the reimbursement for ED only care)and to a lesser degree the cost of expanding to run efficiently with peak ED volumes. Remember some private hospitals essentially did not have EDs!
    There is no doubt that “payment assessments” were encouraged by some private hospitals..sometimes at triage and often in the field.

    COBRA eventually drove out must of the excesses, so the question today is why hospitals still refuse to build, staff and respond to high volumes for predictable(but relatively common) peak loads.They do pretty well in isolated disaster situations.

    In my opinion the problem(in non teaching hospotals) is the availability /cost of dedicated emergency speciality staffing( surgeons, pyschiatrists, and others ). Dedicated places like MIEMSS can still ramp up without disrupting EVERTHING for the next several days, while smaller , geographically isolated hospitals(and the staff)are dysfunctional for at least 24 hours simply because there os not enough staff to
    quickly return to normal/scheduled activities.

  2. Marvin Prichard MD on

    This article presents a more or less complete financial analysis of ambulance diversion. If the hospital’s bottom line were the sole interest of Emergency Medicine, we would need look no further. However, the overcrowded ED which does not divert can be detrimental to patient safety and to EMS efficiency. More acute patients need to be transported to where they can best be treated in a timely manner.
    Any financial analysis needs to account for the legal consequences of bad outcome when the ED is truly unable to accept critical patients.There is also the issue of very ill indigents arriving by ambulance who generate no revenue and much expense when admitted.
    This article can certainly be of value in convincing hospital management to provide the resources we need to expedite flow and reduce overcrowding. All too often, however,
    it may be used to institute a blind “No diversions- No exceptions” policy which serves no one well.

  3. Steve Giordano on

    Dr. Augustine,
    I respectfully wish to add a few points that are harder to quantify. As a Chief Operating Officer I do understand the approach that the researchers took and the importance of these factors on our bottom line. However, as a clinician in an busy community ER, I think that several other factors must be considered. First, when an ER is on diversion, not all ambulance runs are diverted. In Los Angeles County, for example, all Basic Life Support runs are still taken to facilities regardless of diversion status. Many times the Fire Dept or ALS crew in the field will clear patients that are often ill and allow them to be transported BLS. Secondly, all patients deemed “too critical to bypass closest receiving hospital” are still transported to facilities on diversion. Thirdly, sick patients are still arriving as walk-ins. So one cannot simply use an hourly formula to determine the revenue lost based on all of these variables. Lastly, and maybe most importantly are the issues of provider and patient safety. When the decision is made to go on diversion it is because the department status is such that receiving other ill patients would jeopardize the safety of the existing patients and the providers’ ability to safely provide care to these patients. It is also difficult to quantify the impact on customer service to BLS patients on gurneys in the hallway that are consistently pushed aside for incoming ALS runs due to inability to close. Not to mention the effect this has on patients in the waiting room and their growing dissatisfaction with lengthy waits. This is a very complex issue. You mentioned relationships with the EMS community. They are also represented by the EMT’s that must hold the wall on the BLS crews that are holding “less-sick” patients. As I agree that there should be efforts made to mitigate closure and assure a speedy return to “open” status we should also consider the above points. Thank you

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