Emergency department (ED) overcrowding negatively impacts overall quality of care and limits emergency systems' capacity to effectively manage unanticipated surges in demand for medical care secondary to mass casualty incidents or pandemics (Bernstein et al, 2009; Agency for Healthcare Research and Quality, 2004). Given its pervasiveness across many emergency systems in the United States, ED overcrowding is now recognized as a key public health issue (Institute of Medicine, 2006).
Over the last two decades, as a result of increasing financial pressure, hospitals have decreased the total number of inpatient beds and eliminated spare capacity (DeLia and Wood, 2008). In addition, hospitals have increasingly focused on elective admissions with typically higher financial margins. These factors, combined with increasing demand for inpatient services, has led to higher hospital occupancy rates and less inpatient bed availability for admitted ED patients (Bazzoli et al, 2003; Schafermeyer and Asplin, 2003). This trend is expected to persist given the current economic climate and ongoing efforts to reduce costs by Medicare, Medicaid, and private payers.
Using the Input-Throughput-Output conceptual model of ED overcrowding, researchers have identified that poor outflow of admitted ED patients is the most frequent cause of ED overcrowding (Asplin et al, 2003; Moskop et al, 2009) These ‘boarding’ admitted ED patients (those awaiting an inpatient bed) remain in ED rooms thus reducing the ED's capacity to care for newly arriving patients. While poor outflow of admitted ED patients is the key contributor to overcrowding and can be addressed only via hospital-level interventions, EDs are attempting to mitigate the impact of overcrowding by implementing processes focused on input and throughput.
‘So, what happens when diversion is eliminated?’
Total ED visits over the past decade have significantly increased with greater than 25% of all acute care visits and nearly all of after-hours and weekend care occurring in EDs (Pitts et al, 2010). This trend is expected to continue well into the future (Tang et al, 2010). Given this expected growth in total ED visits and the Emergency Medical Treatment and Labor Act (EMTALA) requirement that a qualified medical professional evaluate all patients presenting to an ED, there are limited options available to control the inflow of patients to the emergency system.
One way to control some of the inflow of patients to the ED is through ambulance diversion. Many municipalities allow an ED to divert ambulance traffic to other hospitals when the ED becomes crowded. According to the 2003 Ambulatory Medical Care survey, more than 40% of EDs divert ambulances, or an estimated 500,000 total ambulances were diverted in that year (1 ambulance diverted per minute) (Burt et al, 2006). The underlying premise is that at high levels of overcrowding, quality and safety are compromised; thus, diverting ambulances to less crowded EDs results in better patient outcomes. While this premise seems valid, data are lacking to support the effectiveness of this intervention in reducing overcrowding or improving patient outcomes. In fact, some data exist to the contrary for patients with time sensitive conditions (Shen and Hsia, 2011). Given the limited impact of diversion on reducing overcrowding, and the potential negative impact on patient outcomes, many municipalities and EDs are considering the elimination of ambulance diversion.
So, what happens when diversion is eliminated? The Massachusetts Department of Public Health, with strong support from the Massachusetts chapter of the American College of Emergency Physicians, led the way with a statewide elimination of ambulance diversion in January 2009. While proponents of diversion were concerned about the impact of eliminating diversion on worsening ED overcrowding, studies post elimination of diversion have shown that there was no impact on overall ED volume (Friedman et al, 2011). In addition, those hospitals expecting an increase in ambulance traffic implemented interventions such as surge pods or physician-in-triage to handle this increase (SoRelle, 2009).
Given the limited value of diversion, we describe below the criteria that must be considered by municipalities and hospitals when contemplating elimination of diversion.
For ambulance diversion to be an effective strategy in an emergency system, three criteria must be met:
Ambulance traffic must be a key contributor to overall ED volume
Patients arrive at EDs either by ambulance or ‘walk-in’. Recent studies have demonstrated that less than 15% of ED patients arrive via ambulance (Niska et al, 2010). Municipalities or emergency departments considering eliminating diversion must consider their overall ambulance volume especially during the hours of peak ED overcrowding. The less ambulance transport an ED receives, especially during peak ED overcrowding hours, the less useful ambulance diversion is as a tool for controlling ED overcrowding.
In addition, hospitals must consider the rate of hospital admission of their patients arriving via ambulance. High rates of admission will impact available inpatient beds and secondarily ED overcrowding. For hospitals with lower admission rates of patients arriving by ambulance, eliminating diversion will have relatively less impact on boarding or exacerbating the overcrowding problem.
Spare capacity must exist within the regional emergency system to absorb the diverted traffic
The lack of spare capacity within a regional emergency system leads to a domino effect that is well described in the literature (Sun et al, 2006). When spare capacity does not exist, an ED diverting its ambulance traffic increases overcrowding at nearby EDs, who in turn need to ‘go on diversion’. As more EDs in the system are simultaneously on diversion, municipalities typically have to halt diversion at all EDs. The domino effect thus incentivizes EDs to go on diversion early to control their inflow in anticipation of the downstream effect for neighbouring EDs going on diversion. Prior to elimination of ambulance diversion in Boston, this domino effect was well described and was a key reason for the elimination of diversion (SoRelle, 2009). The domino effect is the main reason why there must be coordination to eliminate diversion at a system level as an individual ED unilaterally eliminating diversion may worsen that ED's overcrowding problem.
Quality of care, factoring ED overcrowding, transport times, and hospital capabilities, must be the same or better
In an emergency system where spare capacity exists and ambulance traffic contributes significantly to overall volume, the last criterion that must be addressed is the impact of ambulance diversion on patient outcomes.
In principle, ambulance diversion reroutes traffic to less crowded hospitals at the expense of increasing transport times and/or decreasing hospital capabilities. Judging the impact of these tradeoffs on quality of care is the hardest factor to measure when considering the impact of diversion.
Proponents of diversion highlight the impact of ED overcrowding on the outcomes of patients with critical conditions such as chest pain or other time sensitive complaints. This impact they argue, justifies diverting patients from crowded EDs to less crowded EDs. While this may be a legitimate reason, contradictory evidence exists on the impact of overcrowding on quality of care for patients with time-sensitive conditions (Shen and Hsia, 2011). In addition, while several studies describe the impact of overcrowding on delays in delivering treatments, very little evidence exists on the impact of overcrowding on outcomes, especially for discharged ED patients (Pines and McCarthy, 2011).
In a recent study of patients with Acute Myocardial Infarction (AMI), diversion was shown to lead to worse outcomes (Shen and Hsia, 2011; Begley et al, 2004). This is of increasing concern given recent studies that show no difference in the care of patients with similar time-sensitive conditions such as AMI and stroke, even when the ED is crowded. (Chatterjee et al, 2011; Harris et al, 2011) The majority of EDs have protocols in place to expedite the management of patients with these conditions and have the ability to create the needed capacity to care for these patients even in the midst of severe overcrowding. While the impact of diversion on outcomes may be related to the hospital characteristics of high-diversion hospitals rather than diversion itself, the utility of diversion is still limited and thus eliminating diversion will at worst have little impact on the quality of care for these patients with time sensitive high acuity complaints (Soremekun et al, 2011).
Ambulance diversion with healthcare and payment reforms
Diverting patients receiving complicated tertiary services from their primary hospitals is recognized as an inefficient use of resources and leaves many patients dissatisfied. As payment and healthcare reforms in the United States move towards bundled payments for episodes of care and accountable care organizations, delivering the right patient to the right place at the right time will become an increasingly important function of EMS systems. These payment reforms incentivize hospitals to take increased responsibility for the overall care of their patients. This requires increased access to emergency services and will further prevent hospitals from going on diversion. While the role pre-hospital transport will play with payment reforms has not been well elucidated, patient and hospitals will increasingly push for transporting the patient to the right hospital.
Conclusion
While further study is needed to increase our understanding of the impact of diversion on the quality of care provided, the lack of spare capacity in most regional emergency systems, the relatively small fraction of overall ED volume that arrives via ambulance, and payment reforms make ambulance diversion an ineffective and soon to be obsolete intervention.