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EMS Reverse Triage

Editor: J R. Walker, III Updated: 8/8/2023 1:15:27 AM


Healthcare systems are supply constrained systems with unpredictable and fluctuating levels of demand. When the level of demand outpaces the available supply of resources, the healthcare system must make decisions on how to allocate available resources. In extremes of demand, such as mass casualty incidents or natural disasters, the healthcare system may be impaired to the point of near non-operation due to overwhelming need. Hospitals are expected to be able to maintain functionality for up to 96 hours without external resources, but to remain functional in the face of extreme demand, hospital systems must increase available resources or find ways to redistribute resources in more efficient ways.[1] There is an increasing academic effort to develop ways to help hospitals and other healthcare systems deal with surging unanticipated demand. Inspired by a military tactic of treating the least injured soldiers first so that limited resources could then be focused on the more critically injured, reverse triage is a method that has been recommended in the literature as a way to combat situations of unusually high demand. Reverse triage is a way to refocus hospital resources on critically ill patients in the field or the emergency department by identifying and discharging admitted patients who have a relatively small risk of complication if discharged early, thus ensuring the best reduction in morbidity and mortality for the greatest number of patients while treating the largest number of patients in the shortest period of time.[1]

Issues of Concern

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Issues of Concern

In healthcare systems across the country, there are periods when demand for healthcare services spike to levels above the baseline level of demand. These “surge” periods of demand place stress on the healthcare system, especially those areas with already scant resources. Each system can handle surge demand to different degrees based on the availability of resources and ability to maximize their effectiveness. Surge capacity is the maximum amount of resources that can potentially be available during a given period.[2] Hospitals normally operate at a baseline capacity, but can rapidly increase this capacity by increasing the number of resources available or by changing management of available resources. Common ways hospitals currently increase capacity include calling in additional staff, opening “pop-up” inpatient units, and canceling elective surgeries or admissions. In times of extreme resource demand, as in mass casualty incidents or disasters, even these normal capacity enhancing techniques can quickly be overwhelmed. Most healthcare systems implement triage systems to detect which patients are the most critical and will potentially require the most resources. Reverse triage (in this situation) is a method to redistribute resources to those patients who need them most by identifying the least critical patients who require the least amount of resources.[1]

In periods of extreme surge, when demand outruns supply, the hospital must decide which patients should receive access to the finite supply of resources, such as ventilators or blood products. In most hospital systems, inpatient beds are one of the first resources to be consumed when demand increases.[2] Reverse triage helps to address this critical deficiency by opening inpatient beds to those who need them most. In recent pilot trials of reverse triage, investigators have suggested that 10% to 20% of total bed capacity can be made available within the first 2 to 6 hours, with the full effect of a reverse triage system occurring at 24 to 48 hours.[1]

A group of researchers at Johns Hopkins University and a panel of experts in the field of emergency medicine and disaster preparedness developed the reverse triage system to address the constraints of inpatient capacity during a disaster event.[3] For a reverse triage system to operate as designed, the panel laid out certain assumptions essential to a safe and effective system. These assumptions can be grouped into two general categories: patient-centered and system-based. Regarding the first, quality of patient care is paramount and must not be sacrificed for the sake of increased capacity. Patients deemed safe for discharge will only have basic care available in the community after dismissal.[3] Patients who have a very poor prognosis, critical care patients, and pediatric patients are considered separately from the general inpatient population.[4] In the second category, hospital systems will have a predetermined disaster plan in place which allows the hospital to remain open and functional. The system will begin to receive any necessary outside assistance within 48 to 72 hours.[3] In addition, to reverse triage, hospital systems should continue to improve capacity with other means.

With the previous assumptions in mind, the challenge of reverse triage is to determine which inpatients can be safely discharged. According to the expert panel, a patient is considered a candidate for early discharge if there is not a significant risk for a consequential medical event, including irreversible impairment, unexpected death, or a reduction in function within 72 hours of hospital discharge.[3] These events are only considered consequential if a critical intervention would be necessary to stabilize or improve the condition. Critical interventions exist on a spectrum of necessity and ability to address a consequential event, ranging from cardiopulmonary resuscitation (CPR) to basic assistance with activities of daily living.[3] Therefore, the more likely a patient is to need critical interventions, the less likely a patient should be chosen for early discharge by reverse triage.

When evaluating patients for the likelihood of consequential medical events, it is important to remember that even normally discharged patients carry some amount of risk for adverse events after they leave the hospital. One study has estimated that adverse events occur in up to 19% of routinely discharged patients and up to 12% of discharged patients have a preventable adverse event.[5] This baseline risk provides a starting point when evaluating inpatients for the likelihood of consequential medical events and determining individual patient risk when considered for early discharge by reverse triage.

In order to choose the most appropriate patients for early discharge, a standardized system of inpatient classification was developed to allow practitioners to risk stratify inpatients and determine the safest disposition. A 5-point system for inpatient risk stratification was developed, ranging from minimum risk (1) to very high risk (5), with maximum risk tolerance determined for each level. The first and lowest risk group is those patients who have less than 4% risk of consequential medical events, such as a patient with normal vital signs who could be transitioned to oral antibiotics for a simple infection or oral anticoagulants for an uncomplicated deep venous thrombosis.[3] The minimum risk grouping can be considered safe for immediate discharge. The second risk grouping is for those patients who have less than 12% risk of needing a critical intervention. This low-risk group may have an increased incidence of non-fatal medical events and would likely be best dispositioned to family care or very low acuity facilities. The third risk grouping, or moderate risk, is the first group in which discharge to home care is not advised, as this group can have up to 33% risk of consequential events. Patients in this class are appropriate for transfer to moderate-acuity or skilled-nursing facilities and could include patients who underwent recent major surgery and need intravenous pain medications and antibiotics. The fourth risk group, those at high risk, have up to 61% risk associated with their medical care. These patients are only suitable for transfer to other major acuity facilities and any delay in care will likely lead to loss of life or limb. For example, a patient who has a strangulated hernia who needs emergency surgery, a patient in active labor, or a patient with septic shock requiring intravenous vasopressors but not airway support. Finally, the level 5, or very high risk, group includes patients who are unable to be moved making them generally unstable for transport, have associated consequential medical events up to 92% of the time, and include most intensive care unit patients.[3]

Once inpatients are appropriately classified into risk categories, appropriate dispositions can be initiated. Although the goal is to create inpatient capacity, one potential limitation of the reverse triage system is that early discharged patients may return to the hospital due to a consequential medical event, worsening of the condition, or inappropriate discharge, and lead to a further surge in demand. This safety net of returning for additional evaluation and management is, however, necessary to prevent patients from having a bad outcome who have been processed under a reverse triage system. Patients should be informed to return for any worsening or failure to improve as expected. Patients that return to already strained healthcare systems pose additional challenges that must be addressed. For example, one study suggests that patients who return to the emergency department after hospital discharge require longer times in treatment and are twice as likely to be readmitted to the hospital.[6] Patients that return to the healthcare system after discharge have longer stays, higher charges, and, due to the higher likelihood of admission, create further demand for limited resources, thereby undermining the efficiency of the reverse triage system.[1]

Techniques to address surging healthcare demand are an ongoing area of research as hospital systems across the country are facing increased demand with a limited supply of resources. Although reverse triage has been proposed as a tool to combat a surge in a mass casualty or disaster event, several hospitals are evaluating the feasibility of using the reverse triage system to address more routine surge situations such as emergency department overcrowding.[2] This is an undesirable application of this tool, as it fails to address the underlying root cause of the problem, which is inpatient hospital bed availability. Reverse triage is meant to combat a singular overwhelming event that is unlikely to re-occur on a reasonable time line, so it is self-limiting by design. Although the reverse triage system could be applied in much the same way to daily boarding and poor hospital flow planning, the level of risk that is acceptable for a discharged patient will be much lower in the normal day to day operations of a hospital system when compared to extreme events.[2] As the tolerable level of risk decreases, the magnitude of the effect of reverse triage will also decrease. Each hospital must decide which level of risk is acceptable in each situation and determine whether the increase in capacity justifies the increased risk.

Clinical Significance

In the event of a disaster, mass casualty incident or epidemic, hospital systems face a significant demand for healthcare services that often outpaces the supply of resources available. Developing techniques to handle these periods of surge demand are critical for allowing healthcare systems to continue functioning in the face of supply constraints. Reverse triage is one tool that can be implemented to allow the judicious use of resources to provide the most beneficial care to the greatest number of patients. Discharging inpatients who can safely continue their medical care at an outside acute care facility or private residence opens hospital beds that can then be used for more critically ill patients. Despite the benefits of reverse triage in increasing hospital capacity, a standardized system should be used to determine which patients can be safely discharged to limit the morbidity and mortality associated with premature discharge. Hospital systems should evaluate the discharge criteria used in reverse triage at the individual system level as risk tolerance, capacity needs, and post-discharge resources vary from system to system to increase the effect of reverse triage while maintaining a high quality of care.



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Kelen GD, McCarthy ML. The science of surge. Academic emergency medicine : official journal of the Society for Academic Emergency Medicine. 2006 Nov:13(11):1089-94     [PubMed PMID: 17085736]


Kelen GD, Kraus CK, McCarthy ML, Bass E, Hsu EB, Li G, Scheulen JJ, Shahan JB, Brill JD, Green GB. Inpatient disposition classification for the creation of hospital surge capacity: a multiphase study. Lancet (London, England). 2006 Dec 2:368(9551):1984-90     [PubMed PMID: 17141705]


Kelen GD,McCarthy ML,Kraus CK,Ding R,Hsu EB,Li G,Shahan JB,Scheulen JJ,Green GB, Creation of surge capacity by early discharge of hospitalized patients at low risk for untoward events. Disaster medicine and public health preparedness. 2009 Jun     [PubMed PMID: 19349868]


Forster AJ, Murff HJ, Peterson JF, Gandhi TK, Bates DW. The incidence and severity of adverse events affecting patients after discharge from the hospital. Annals of internal medicine. 2003 Feb 4:138(3):161-7     [PubMed PMID: 12558354]


Baer RB, Pasternack JS, Zwemer FL Jr. Recently discharged inpatients as a source of emergency department overcrowding. Academic emergency medicine : official journal of the Society for Academic Emergency Medicine. 2001 Nov:8(11):1091-4     [PubMed PMID: 11691674]

Level 2 (mid-level) evidence