Emergency Severity Index (ESI): A Triage Tool for Emergency Department
Chapter 4. ESI Levels 3-5 and Expected Resource Needs
Traditionally, comprehensive triage has been the dominant model for triage acuity assignment in U.S. emergency departments (Gilboy, 2010; Gilboy, Travers, & Wuerz, 1999). Triage acuity rating systems have been based solely on the acuity of the patient, determined through the nurse's assessment of vital signs, subjective and objective information, past medical history, allergies, and medications. Such systems require the nurse to assign an acuity level by making a judgment about how sick the patient is and how long the patient can wait to be seen by a provider.
The ESI triage system uses a novel approach that includes not only the nurse's judgments about who should be seen first, but also, for less acute patients (those at ESI levels 3 through 5), calling on the nurse to add predictions of the resources that are likely to be used to make a disposition for the patient.
This chapter includes background information on the inclusion of resource predictions in the ESI and a description of what constitutes a resource. Examples are given of patients rated ESI levels 3 to 5 and the resources that each patient is predicted to need.
Estimation of resource needs begins only after it has been determined that the patient does not meet ESI level 1 or 2 criteria. The nurse then predicts the number of resources a patient will need in order for a disposition to be reached. When Wuerz and Eitel created the ESI triage system, they included resource utilization to provide additional data and allow a more accurate triage decision. They believed that an experienced emergency department (ED) triage nurse would be able to predict the nature and number of tests, therapeutic interventions, and consultations that a patient would need during his/her ED stay. Studies of ESI implementation and validation have verified that triage nurses are able to predict ED patients' resource needs (Eitel, Travers, Rosenau, Gilboy, & Wuerz, 2003; Tanabe, Gimbel, Yarnold, & Adams, 2004). One study was conducted at seven EDs representing varied regions of the country, urban and rural areas, and academic and community hospitals. Nurses were able to predict how many ESI-defined resources the ED patients required 70 percent of the time. That is, experienced triage nurses can reasonably predict at triage how many resources patients will require to reach ED disposition; more importantly, they can discriminate at presentation low versus high resource intensity patients. This differentiation by resource requirements allows for much more effective streaming of patients at ED presentation into alternative operational pathways within the ED, that is, the parallel processing of patients. Research has also established that ESI triage levels correlate with important patient outcomes, including admission and mortality rates (Eitel et al., 2003).
Again, it is important to note that resource prediction is only used for less acute patients. At decision points A and B on the ESI algorithm (Figure 4-1), the nurse decides which patients meet criteria for ESI levels 1 and 2 based only on patient acuity. However, at decision point C, the nurse assigns ESI levels 3 to 5 by assessing both acuity and predicted resource needs. Thus, the triage nurse only considers resources when the answers to decision points A and B are "no."
To identify ED patients' resource needs, the triage nurse must have familiarity with general ED standards of care, and specifically with what constitutes prudent and customary emergency care. An easy way to think about this concept is to ask the question, "Given this patient's chief complaint, what resources are the emergency providers likely to utilize?" Another way to look at this is to consider, "What is it going to take for a disposition to be reached?" Disposition can be admission, discharge, or transfer.
The triage nurse uses information from the brief subjective and objective triage assessment—as well as past medical history, medications, age, and gender—to determine how many different resources will be needed for the ED provider to reach a disposition. For example, a healthy teenage patient with a simple leg laceration and no prior medical history would need only one resource: suturing. On the other hand, an older adult with multiple chronic medical problems and no history of dizziness who presents with a head laceration from a fall will clearly need multiple resources: suturing, blood/urine tests, ECG, head CT, or consultations with specialists. Accurate use of ESI triage is contingent on the nurse's ability to accurately predict resources and as such is best performed by an experienced emergency nurse.
Guidelines for the categorization of resources in the ESI triage system are shown in Table 4-1. ESI levels 3, 4, and 5 are differentiated by the nurse's determination of how many different resources are needed to make a patient disposition. On the basis of the triage nurse's predictions, patients who are expected to consume no resources are classified as ESI level 5, those who are likely to require one resource are ESI level 4, and those who are expected to need two or more resources are designated as ESI level 3. Patients who need two or more resources have been shown to have higher rates of hospital admission and mortality and longer lengths of stay in the ED (Eitel et al., 2003; Tanabe, Gimbel, Yarnold, Kyriacou, & Adams, 2004).
Table 4-1. Resources for the ESI Triage System
|Labs (blood, urine)
|History & physical (including pelvic)
|ECG, x-rays CT-MRI-ultrasound angiography
|IV fluids (hydration)
|Saline or heplock
|IV, IM or nebulized medications
|Phone call to PCP
|Simple procedure = 1 (lac repair, Foley cath)
|Simple wound care (dressings, recheck)
|Complex procedure = 2 (conscious sedation)
|Crutches, splints, slings
Though the list of resources in Table 4-1 is not exhaustive, it provides general guidance on the types of diagnostic tests, procedures, and therapeutic treatments that constitute a resource in the ESI system. Emergency nurses who use the ESI are cautioned not to become overly concerned about the definitions of individual resources. It is important to remember that ESI requires the triage nurse to merely estimate resources that the patient will need while in the ED. The most common resources are listed in Table 4-1; however a comprehensive list of every possible ED resource is neither practical nor necessary. In fact, all that is really necessary for accurate ESI rating is to predict whether the patient will need no resources, one resource, or two or more resources. Once a triage nurse has identified two probable resources, there is no need to continue to estimate resources. Counting beyond two resources is not necessary.
The essence of the ESI resource component is to separate more complex (resource-intensive) patients from those with simpler problems. The interventions considered as resources for the purposes of ESI triage are those that indicate a level of assessment or procedure beyond an exam or brief interventions by ED staff and/or involve personnel outside of the ED. Resources that require significant ED staff time (such as intravenous medication administration or chest tube insertion) and those that require staff or resources outside the ED (such as x-rays by the radiology staff or surgical consults) increase the patient's ED length of stay and indicate that the patient's complexity, and, therefore, triage level is higher.
There are some common questions about what is considered an ESI resource. One question often asked is about the number of blood or urine tests and x-rays that constitute a resource. In the ESI triage method, the triage nurse should count the number of different types of resources needed to determine the patient's disposition, not the number of individual tests:
- A complete blood count (CBC) and electrolyte panel comprise one resource (lab test).
- A CBC and chest x-ray are two resources (lab test, x-ray).
- A CBC and a urinalysis are both lab tests and together count as only one resource.
- A chest x-ray and kidneys, ureters, and bladder x-ray are one resource (x-ray).
- Cervical-spine films and a computerized tomography (CT) scan of the head are two resources (x-ray and CT scan).
It is important for emergency nurses to understand that not every intervention they perform can be counted as a resource. For example crutch walking education, application of a sling and swath, or application of a knee immobilizer all take time but do not count as a resource. If, for example a splint did count, patients with sprained ankles would be triaged as ESI level 3 (x-ray and splint application). While the application of a splint can certainly take time, it is important to remember the only purpose of resource prediction with ESI is to sort patients into distinct groups and help get the right patient to the right area of the ED. Another example is a patient with a laceration who may require suturing and a tetanus booster If a tetanus booster (IM medication) "counted," any patient with a laceration who needed suturing and a tetanus booster would meet ESI Level 3 criteria. In many EDs, ESI level-3 patients are not appropriate for a fast track or urgent care area. Remember, triage level is not a measure of total nursing workload intensity; it is a measure of presentational acuity.
Another common question about ESI resources relates to the fact that eye irrigation is also considered a resource. Patients with a chemical splash usually meet ESI level-2 criteria because of the high-risk nature of the splash, so eye irrigation is not a key factor in their ESI rating. However, if the eye problem was due to dust particles in the eye, the patient would not necessarily be high risk. In this type of patient, the eye irrigation would count as a resource and the patient would meet ESI level-4 criteria. The eye exam does not count as a resource because it is considered part of the physical exam.
Another frequent question posed by clinicians is related to the items listed as "not resources" in Table 4-1. The purpose of the list is to assist triage nurses with quick, accurate sorting of patients into five clinically distinct levels (Wuerz, Milne, Eitel, Travers & Gilboy, 2000). As such, items listed as not being resources include physical exams, point-of-care tests, and interventions that tend not to lead to increased length of stay in the ED or indicate a higher level of complexity. Since the standard of care is that all ED patients undergo a basic history and physical exam, an exam does not constitute a resource for ESI classification. For the female patient with abdominal pain, a pelvic exam would be part of the basic physical exam. A patient with an eye complaint would need a slit lamp exam as part of the basic physical exam. The strength of the ESI is its simplicity; the true goal of the resource determination is to differentiate the more complicated patients needing two or more resources (level 3 or above) from those with simpler problems who are likely to need fewer than two resources (level 4 or 5). Emergency nurses should not try to complicate ESI by concentrating overly on resource definitions. Usually, a patient requires either no resources, one resource, or two or more resources.
Though resource consumption may vary by site, provider, and even individual patient, triage nurses are urged to make the ESI resource prediction by thinking about the common approaches to the most common presenting problems. Ideally, a patient presenting to any emergency department should consume the same general resources. For example, a provider seeing a hemodynamically stable 82-year-old nursing home resident who has an in-dwelling urinary catheter and a chief complaint of fever and cough will most likely order blood and urine tests and a chest x-ray. The triage nurse can accurately predict that the patient needs two or more resources and therefore classify the patient as ESI level 3.
There may be minor variations in operations at different EDs, but this will rarely affect the triage rating. For example, some departments do pregnancy tests in the ED (point of care testing is not a resource by ESI) and others send them to the lab (a resource by ESI). However, patients rarely have the pregnancy test as their only resource, so most of those patients tend to have two or more resources in addition to the pregnancy test. One ED practice variation that may result in different ESI levels for different sites is the evaluation of patients with an isolated complaint of sore throat. At some hospitals it is common practice to obtain throat cultures (one resource, ESI level 4), while at others it is not (no resources, ESI level 5). Evidence-based practice guidelines are being used more and more to determine the need for x-rays or other interventions. One example is the use of the Ottawa Ankle Rules. These are validated rules used to determine the need for an x-ray of the ankle for patients that present with ankle injuries. Institutional adoption of these rules into practice varies. Institutions that use these rules at triage may obtain fewer x-rays when compared with institutions that do not routinely use these rules.
When counting resources the triage nurse should not consider which physician, nurse practitioner or physician's assistant is working. There are practice differences among providers but the triage nurse has to focus on what is prudent and customary.
Temperature is an important assessment parameter for determining the number of resources for very young children. This subject will be covered in Chapter 5.
From a clinical standpoint, ESI level 4 and 5 patients are stable and can wait several hours to be seen by a provider. However, from a customer service standpoint, these patients are perhaps better served in a fast-track or urgent care area. Mid-level practitioners with the appropriate skills mix and supervision could care for level-4 and level-5 patients. With ESI, level-5 patients can sometimes be "worked in" for a quick exam and disposition by the provider, even if the department is at capacity. Often triage policies clearly state ESI level-4 or -5 patients can be triaged to an urgent care or fast-track area.
In summary, the ESI provides an innovative approach to ED triage with the inclusion of predictions about the number of resources needed to make a patient disposition. Consideration of resources is included in the triage level assignment for ESI level-3, -4, and -5 patients, while ESI level-1 and 2 decisions are based only on patient acuity. Examples of ESI level-3, -4, and -5 patients are shown in Table 4-2. Practical experience has demonstrated that resource estimation is very beneficial in helping sort the large number of patients with non-acute presentations. Common questions about resources are addressed in the Chapter 4 Frequently Asked Questions section of Appendix A.
Note: Appendix A of this handbook includes frequently asked questions and post-test assessment questions for Chapters 2 through 8. These sections can be incorporated into a locally-developed ESI training course.
Eitel DR, Travers DA, Rosenau A, Gilboy N, Wuerz RC (2003). The emergency severity index version 2 is reliable and valid. Acad Emerg Med 10(10):1079-1080.
Gilboy N. (2010). Triage. In PK Howard and RA Steinmann (Eds) Sheehy's Emergency Nursing Principles and Practice (59-72). St. Louis: Mosby.
Gilboy N, Travers DA, Wuerz RC (1999). Re-evaluating triage in the new millennium: A comprehensive look at the need for standardization and quality. JEN 25(6):468-473.
Tanabe P, Gimbel R, Yarnold PR, Adams J (2004). The emergency severity index (v. 3) five level triage system scores predict ED resource consumption. JEN 30:22-29.
Tanabe P, Gimbel R, Yarnold PR, Kyriacou D, Adams J (2004). Reliability and validity of scores on the Emergency Severity Index Version 3. Acad Emerg Med 11:59-65.
Wuerz R, Milne LW, Eitel DR, Travers D, Gilboy N (2000). Reliability and validity of a new five-level triage instrument.Acad Emerg Med 7(3):236-242.
Page last reviewed October 2014