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Emergency Severity Index (ESI) Implementation Handbook, 2012 Edition

Chapter 2. Overview of the Emergency Severity Index

Chapter 2. Overview of the Emergency Severity Index

The Emergency Severity Index (ESI) is a simple to use, five-level triage algorithm that categorizes emergency department patients by evaluating both patient acuity and resource needs. Initially, the triage nurse assesses only the acuity level. If a patient does not meet high acuity level criteria (ESI level 1 or 2), the triage nurse then evaluates expected resource needs to help determine a triage level (ESI level 3, 4, or 5). The ESI is intended for use by nurses with triage experience or those who have attended a separate, comprehensive triage educational program.

Inclusion of resource needs in the triage rating is a unique feature of the ESI in comparison with other triage systems. Acuity is determined by the stability of vital functions and the potential threat to life, limb, or organ. The triage nurse estimates resource needs based on previous experience with patients presenting with similar injuries or complaints. Resource needs are defined as the number of resources a patient is expected to consume in order for a disposition decision (discharge, admission, or transfer) to be reached. Once oriented to the algorithm, the triage nurse will be able to rapidly and accurately triage patients into one of five explicitly defined and mutually exclusive levels.

This chapter presents a step-by-step description and overview of how to triage using the ESI algorithm. Subsequent chapters explain key concepts in more detail and provide numerous examples to clarify the finer points of ESI.

Algorithms are frequently used in emergency care. Most emergency clinicians are familiar with the algorithms used in courses such as Basic Life Support, Advanced Cardiac Life Support, and the Trauma Nursing Core Course. These courses present a step-by-step approach to clinical decision making that the clinician is able to internalize with practice. The ESI algorithm follows the same principles.

Each step of the algorithm guides the user toward the appropriate questions to ask or the type of information to gather. Based on the data or answers obtained, a decision is made and the user is directed to the next step and ultimately to the determination of a triage level.

A conceptual overview of the ESI algorithm is presented in Figure 2-1 to illustrate the major ESI decision points. The ESI algorithm itself is shown in Figure 2-1a. The algorithm uses four decision points (A, B, C, and D) to sort patients into one of the five triage levels. Triage with the ESI algorithm requires an experienced ED nurse, who starts at the top of the algorithm. With practice, the triage nurse will be able to rapidly move from one ESI decision point to the next.

The four decision points depicted in the ESI algorithm are critical to accurate and reliable application of ESI. The figure shows the four decision points reduced to four key questions:

  1. Does this patient require immediate life-saving intervention?
  2. Is this a patient who shouldn't wait?
  3. How many resources will this patient need?
  4. What are the patient's vital signs?

The answers to the questions guide the user to the correct triage level.

Decision Point A: Does the Patient Require Immediate Life-Saving Intervention?

Simply stated, at decision point A (Figure 2-2) the triage nurse asks, "Does this patient require immediate life saving intervention?" If the answer is "yes," the triage process is complete and the patient is automatically triaged as ESI level 1. A "no" answer moves the user to the next step in the algorithm, decision point B.

Figure 2-2. Decision Point A: Is the Patient Dying?

In this figure, a box labeled A 'requires immediate life-saving intervention' has two arrows leaving it. One is labeled 'no,' and the other is labeled 'yes' and points to the number 1 (for triage level 1).

The following questions are used to determine whether the patient requires an immediate lifesaving intervention:

  • Does this patient have a patent airway?
  • Is the patient breathing?
  • Does the patient have a pulse?
  • Is the nurse concerned about the pulse rate, rhythm, and quality?
  • Was this patient intubated pre-hospital because of concerns about the patient's ability to maintain a patent airway, spontaneously breathe, or maintain oxygen saturation?
  • Is the nurse concerned about this patient's ability to deliver adequate oxygen to the tissues?
  • Does the patient require an immediate medication, or other hemodynamic intervention such as volume replacement or blood?
  • Does the patient meet any of the following criteria: already intubated, apneic, pulseless, severe respiratory distress, SpO2 < 90 percent, acute mental status changes, or unresponsive?

Research has demonstrated that the triage nurse is able to accurately predict the need for immediate lifesaving interventions (Tanabe, et al., 2005). Table 2-1 lists interventions that are considered lifesaving and those that are not, for the purposes of ESI triage.

Interventions not considered lifesaving include some interventions that are diagnostic or therapeutic, but none that would save a life. Lifesaving interventions are aimed at securing an airway, maintaining breathing, supporting circulation or addressing a major change in level of consciousness (LOC).

The ESI level-1 patient always presents to the emergency department with an unstable condition. Because the patient could die without immediate care, a team response is initiated: the physician is at the bedside, and nursing is providing critical care. ESI level-1 patients are seen immediately because timeliness of interventions can affect morbidity and mortality.

Table 2-1. Immediate Life-saving Interventions

 Life-savingNot life-saving
  • BVM ventilation.
  • Intubation.
  • Surgical airway.
  • Emergent CPAP.
  • Emergent BiPAP.
Oxygen administration:
  • Nasal cannula.
  • Non-rebreather.
Electrical Therapy
  • Defibrillation.
  • Emergent cardioversion.
  • External pacing.
Cardiac Monitor
  • Chest needle decompression.
  • Pericardiocentesis.
  • Open thoracotomy.
  • Intraoseous access.
Diagnostic Tests:
  • ECG.
  • Labs.
  • Ultrasound.
  • FAST (Focused abdominal scan for trauma).
  • Significant IV fluid resuscitation.
  • Blood administration.
  • Control of major bleeding.
  • IV access.
  • Saline lock for medications.
  • Naloxone.
  • D50.
  • Dopamine.
  • Atropine.
  • Adenocard.
  • ASA.
  • IV nitroglycerin.
  • Antibiotics.
  • Heparin.
  • Pain medications.
  • Respiratory treatments with beta agonists.

Immediate physician involvement in the care of the patient is a key difference between ESI level-1 and ESI level-2 patients. Level-1 patients are critically ill and require immediate physician evaluation and interventions. When considering the need for immediate lifesaving interventions, the triage nurse carefully evaluates the patient's respiratory status and oxygen saturation (SpO2). A patient in severe respiratory distress or with an SpO2 <90 percent may still be breathing, but is in need of immediate intervention to maintain an airway and oxygenation status. This is the patient who will require the physician in the room ordering medications such as those used for rapid sequence intubation or preparing for other interventions for airway and breathing.

Each patient with chest pain must be evaluated within the context of the level-1 criteria to determine whether the patient requires an immediate life-saving intervention. Some patients presenting with chest pain are very stable. Although they may require a diagnostic electrocardiogram (ECG) within 10 minutes of arrival, these patients do not meet level-1 criteria. However, patients who are pale, diaphoretic, in acute respiratory distress or hemodynamically unstable do meet level-1 criteria and will require immediate life-saving interventions.

When determining whether the patient requires immediate life-saving intervention, the triage nurse must also assess the patient's level of responsiveness. The ESI algorithm uses the AVPU (alert, verbal, pain, unresponsive) scale (Table 2-2). The goal for this part of the algorithm is to identify the patient who has a recent and/or sudden change in level of conscience and requires immediate intervention. The triage nurse needs to identify patients who are non-verbal or require noxious stimuli to obtain a response. ESI uses the AVPU scale and patients that score a P (pain) or U (unresponsive) on the AVPU scale meet level-1 criteria. Unresponsiveness is assessed in the context of acute changes in neurological status, not for the patient who has known developmental delays, documented dementia, or aphasia. Any patient who is unresponsive, including the intoxicated patient who is unresponsive to painful stimuli, meets level-1 criteria and should receive immediate evaluation. An example of a recent mental status change that would require immediate intervention would be a patient with decreased mental status who is unable to maintain a patent airway or is in severe respiratory distress.

Table 2-2 Four Levels of the AVPU Scale

AVPU levelLevel of consciousness
AAlert. The patient is alert, awake and responds to voice. The patient is oriented to time, place and person. The triage nurse is able to obtain subjective information.
VVerbal. The patient responds to verbal stimuli by opening their eyes when someone speaks to them. The patient is not fully oriented to time, place, or person.
PPainful. The patient does not respond to voice, but does respond to a painful stimulus, such as a squeeze to the hand or sternal rub. A noxious stimulus is needed to elicit a response.
UUnresponsive. The patient is nonverbal and does not respond even when a painful stimulus is applied
Emergency Nurses Association, 2000

An ESI level-1 patient is not always brought to the emergency department by ambulance. The patient or his or her family member may not realize the severity of the illness and, instead of calling an ambulance, may drive the patient to the emergency department. The patient with a drug overdose or acute alcohol intoxication may be dropped at the front door. Infants and children, because they are "portable," may be brought to the ED by car and carried into the emergency department. The experienced triage nurse is able to instantly identify this critical patient. With a brief, "across-the-room" assessment, the triage nurse recognizes the patient that is in extremis. Once identified, this patient is taken immediately to the treatment area and resuscitation efforts are initiated.

Patients assessed as an ESI level 1 constitute approximately 1 percent to 3 percent of all ED patients (Eitel, et al., 2003; Wuerz, Milne, Eitel, Travers, & Gilboy, 2000; Wuerz, et al., 2001). Upon arrival, the patient's condition requires immediate life saving interventions from either the emergency physician and nurse or the trauma or code team. From ESI research we know that most ESI level-1 patients are admitted to intensive care units, while some die in the emergency department (Eitel, et al., 2003; Wuerz, 2001). A few ESI level-1 patients are discharged from the ED, if they have a reversible change in level of consciousness or vital functions such as with hypoglycemia, seizures, alcohol intoxication, or anaphylaxis.

Examples of ESI level 1:

  • Cardiac arrest.
  • Respiratory arrest.
  • Severe respiratory distress.
  • SpO2 <90.
  • Critically injured trauma patient who presents unresponsive.
  • Overdose with a respiratory rate of 6.
  • Severe respiratory distress with agonal or gasping-type respirations.
  • Severe bradycardia or tachycardia with signs of hypoperfusion.
  • Hypotension with signs of hypoperfusion.
  • Trauma patient who requires immediate crystalloid and colloid resuscitation.
  • Chest pain, pale, diaphoretic, blood pressure 70/palp.
  • Weak and dizzy, heart rate = 30.
  • Anaphylactic shock.
  • Baby that is flaccid.
  • Unresponsive patient with a strong odor of alcohol.
  • Hypoglycemia with a change in mental status.
  • Intubated head bleed with unequal pupils.
  • Child that fell out of a tree and is unresponsive to painful stimuli.

Decision Point B: Should the Patient Wait?

Once the triage nurse has determined that the patient does not meet the criteria for ESI level 1, the triage nurse moves to decision point B (Figure 2-3) At decision point B, the nurse needs to decide whether this patient is a patient that should not wait to be seen. If the patient should not wait, the patient is triaged as ESI level 2. If the patient can wait, then the user moves to the next step in the algorithm.

Figure 2-3. Decision Point B: Should the Patient Wait?

Figure 2-3. Decision Point B: Should the Patient Wait?

The box in this figure is labeled B. The first line is 'high risk situation?' with an 'or' underneath and underneath that, 'confused/lethargic/disoriented?' with an 'or' underneath and underneath that, 'severe pain/distress?' An arrow to the side is labeled 'Yes' and points to the number 2, for triage level 2.

Three broad questions are used to determine whether the patient meets level-2 criteria:

  1. Is this a high-risk situation?
  2. Is the patient confused, lethargic or disoriented?
  3. Is the patient in severe pain or distress?

The triage nurse obtains pertinent subjective and objective information to quickly answer these questions. A brief introduction to ESI level-2 criteria is presented here, while a more detailed explanation of which patients meet ESI level-2 criteria will be presented in Chapter 3.

Is This a High-Risk Situation?

Based on a brief patient interview, gross observations, and finally the "sixth sense" that comes from experience, the triage nurse identifies the patient who is high risk. Frequently the patient's age and past medical history influence the triage nurse's determination of risk.

A high-risk patient is one whose condition could easily deteriorate or who presents with symptoms suggestive of a condition requiring time-sensitive treatment. This is a patient who has a potential threat to life, limb or organ. A high-risk patient does not require a detailed physical assessment or even a full set of vital signs in most cases. The patient may describe a clinical portrait that the experienced triage nurse recognizes as a high-risk situation. An example is the patient who states, "I never get headaches and I lifted this heavy piece of furniture and now I have the worst headache of my life." The triage nurse would triage this patient as ESI level 2 because the symptoms suggest the possibility of a subarachnoid hemorrhage.

When the patient is an ESI level 2, the triage nurse has determined that it would be unsafe for the patient to remain in the waiting room for any length of time. While ESI does not suggest specific time intervals, ESI level-2 patients remain a high priority, and generally placement and treatment should be initiated rapidly. ESI level-2 patients are very ill and at high risk. The need for care is immediate and an appropriate bed needs to be found. Usually, rather than move to the next patient, the triage nurse determines that the charge nurse or staff in the patient care area should be immediately alerted that they have an ESI level 2. Unlike with level-1 patients, the emergency nurse can initiate care through protocols without a physician immediately at the bedside. The nurse recognizes that the patient needs interventions but is confident that the patient's clinical condition will not deteriorate. The nurse can initiate intravenous (IV) access, administer supplemental oxygen, obtain an ECG, and place the patient on a cardiac monitor, all before a physician is needed. Although the physician does not need to be present immediately, he or she should be notified that the patient is there and is an ESI 2.

Examples of high-risk situations:

  • Active chest pain, suspicious for acute coronary syndrome but does not require an immediate life-saving intervention, stable.
  • A needle stick in a health care worker.
  • Signs of a stroke, but does not meet level-1 criteria.
  • A rule-out ectopic pregnancy, hemodynamically stable.
  • A patient on chemotherapy and therefore immunocompromised, with a fever.
  • A suicidal or homicidal patient.

Chapter 3 contains additional information on highrisk situations.

Is the Patient Confused, Lethargic, or Disoriented?

This is the second question to be asked at decision point B. Again the concern is whether the patient is demonstrating an acute change in level of consciousness. Patients with a baseline mental status of confusion do not meet level-2 criteria.

Examples of patients who are confused, lethargic, or disoriented:

  • New onset of confusion in an elderly patient.
  • The 3-month-old whose mother reports the child is sleeping all the time.
  • The adolescent found confused and disoriented Each of these examples indicates that the brain may be either structurally or chemically compromised.

Is the Patient in Severe Pain or Distress?

The third question the triage nurse needs to answer at decision point B is whether this patient is currently in pain or distress. If the answer is "no," the triage nurse is able to move to the next step in the algorithm. If the answer is "yes," the triage nurse needs to assess the level of pain or distress. This is determined by clinical observation and/or a self-reported pain rating of 7 or higher on a scale of 0 to 10. When patients report pain ratings of 7/10 or greater, the triage nurse may triage the patient as ESI level 2, but is not required to assign a level-2 rating.

Pain is one of the most common reasons for an ED visit and clearly all patients reporting pain 7/10 or greater do not need to be assigned an ESI level-2 triage rating. A patient with a sprained ankle presents to the ED and rates their pain as 8/10.This patient's pain can be addressed with simple nursing interventions: wheelchair, elevation and application of ice. This patient is safe to wait and should not be assigned to ESI level 2 based on pain.

In some patients, pain can be assessed by clinical observation:

  • Distressed facial expression, grimacing, crying.
  • Diaphoresis.
  • Body posture.
  • Changes in vital signs - hypertension (HTN), tachycardia, and increased respiratory rate.

The triage nurse observes physical responses to acute pain that support the patient's rating. For example, the patient with abdominal pain who is diaphoretic, tachycardic, and has an elevated blood pressure or the patient with severe flank pain, vomiting, pale skin, and a history of renal colic are both good examples of patients that meet ESI level-2 criteria. The triage nurse should also consider the question, "Would I give my last open bed to this patient?" If the answer is yes, then the patient meets the criteria for ESI level 2.

Chapter 3 provides additional information on ESIlevel 2 and pain.

Severe distress can be physiological or psychological. Examples of distress include the sexual assault victim, the victim of domestic violence, the combative patient, or the bipolar patient who is currently manic.

ESI level-2 patients constitute approximately 20 percent to 30 percent of emergency department patients (Travers, et al., 2002; Wuerz, et al., 2001; Tanabe, Gimbel, et al., 2004). Once an ESI level-2 patient is identified, the triage nurse needs to ensure that the patient is cared for in a timely manner. Registration can be completed by a family member or at the bedside. ESI level-2 patients need vital signs and a comprehensive nursing assessment but not necessarily at triage. Placement in the treatment area is a priority and should not be delayed to finish obtaining vital signs or asking additional questions. ESI research has shown that 50 to 60 percent of ESI level-2 patients are admitted from the ED (Wuerz, et al., 2001).

Decision Point C: Resource Needs

If the answers to the questions at the first two decision points are "no," then the triage nurse moves to decision point C (Figure 2-4).

Figure 2-4. Resource Prediction

The box in this figure is labeled C 'How many different resources are needed?' Underneath are three choices: 'none,' 'one,' and 'many.'

The triage nurse should ask, "How many different resources do you think this patient is going to consume in order for the physician to reach a disposition decision?" The disposition decision could be to send the patient home, admit to the observation unit, admit to the hospital, or even transfer to another institution. This decision point again requires the triage nurse to draw from past experiences in caring for similar emergency department patients. ED nurses need to clearly understand that the estimate of resources has to do with standards of care and is independent of type of hospital (i.e., teaching or non-teaching) location of the hospital (urban or rural), or which provider is working that day. A patient presenting to any emergency department should consume the same general resources in one ED as in any other ED.

Considering the patient's brief subjective and objective assessment, past medical history, allergies, medications, age, and gender, how many different resources will be used in order for the physician to reach a disposition? In other words, what is typically done for the patient who presents to the emergency department with this common complaint? The triage nurse is asked to answer these questions based on his or her assessment of the patient and should not consider individual practice patterns, but rather the routine practice in the particular ED.

To identify resource needs, the triage nurse must be familiar with emergency department standards of care. The nurse must be knowledgeable about the concept of "prudent and customary." One easy way to think about this concept is to ask the question, "Given this patient's chief complaint or injury, which resources are the emergency physician likely to utilize?" Resources can be hospital services, tests, procedures, consults or interventions that are above and beyond the physician history and physical, or very simple emergency department interventions such as applying a bandage. Further explanations and examples are provided in Chapter 4.

A list of what is and is not considered a resource for purposes of ESI triage classification can be found in Table 2-3. ESI level-3 patients are predicted to require two or more resources; ESI level-4 patients are predicted to require one resource; and ESI level-5 patients are predicted to require no resources (Table2-4).

Table 2-3. ESI Resources

ResourcesNot resources
Labs (blood, urine)History & physical (including pelvic)
ECG, X-rays CT-MRI-ultrasound angiographyPoint-of-care testing
IV fluids (hydration)Saline or heplock
IV, IM or nebulized medicationsPO medications Tetanus immunization Prescription refills
Specialty consultationPhone call to PCP
Simple procedure = 1 (lac repair, Foley cath)

Complex procedure = 2 (conscious sedation)

Simple wound care (dressings, recheck)

Crutches, splints, slings

Research has shown that ESI level-3 patients make up 30 percent to 40 percent of patients seen in the emergency department (Eitel et al., 2003; Wuerz et al., 2001). ESI level 3 patients present with a chief complaint that requires an in-depth evaluation. An example is patients with abdominal pain. They often require a more in-depth evaluation but are felt to be stable in the short term, and certainly may have a longer length of stay in the ED. ESI level 4 and ESI level 5 make up between 20 percent and 35 percent of ED volume, perhaps even more in a community with poor primary care access. Appropriately trained mid-level providers with the right skills mix could care for these patients in a fast-track or express care setting, recognizing that a high proportion of these patients have a traumarelated presenting complaint.

Decision Point D: The Patient's Vital Signs

Before assigning a patient to ESI level 3, the nurse needs to look at the patient's vital signs and decide whether they are outside the accepted parameters for age and are felt by the nurse to be meaningful. If the vital signs are outside accepted parameters, the triage nurse should consider upgrading the triage level to ESI level 2. However, it is the triage nurse's decision as to whether or not the patient should be upgraded to an ESI level 2 based on vital sign abnormalities. This is decision point D.

Table 2-4. Predicting Resources

ESI LevelPatient PresentationInterventionsResources
5Healthy 10-year-old child with poison ivyNeeds an exam and prescriptionNone
5Healthy 52-year-old male ran out of blood pressure medication yesterday; BP 150/92Needs an exam and prescriptionNone
4Healthy 19-year-old with sore throat and feverNeeds an exam, throat culture, prescriptionsLab (throat culture)*
4Healthy 29-year-old female with a urinary tract infection, denies vaginal dischargeNeeds an exam, urine, and urine culture, maybe urine hCG, and prescriptionsLab (urine, urine C&S, urine hCG)**
3A 22-year-old male with right lower quadrant abdominal pain since early this morning + nausea, no appetiteNeeds an exam, lab studies, IV fluid, abdominal CT, and perhaps surgical consult2 or more
3A 45-year-old obese female with left lower leg pain and swelling, started 2 days ago after driving in a car for 12 hoursNeeds exam, lab, lower extremity non-invasive vascular studies2 or more

*In some regions throat cultures are not routinely performed; instead, the patient is treated based on history and physical exam. If that is the case the patient would be an ESI level 5.

** All 3 tests count as one resource (Lab).

Vital sign parameters are outlined by age in Figure 2-5. The vital signs used are pulse, respiratory rate, and oxygen saturation and, for any child under age 3, body temperature. Using the vital sign criteria, the triage nurse can upgrade an adult patient who presents with a heart rate of 104, or this patient can remain ESI level 3. A 6-month-old baby with a cold and a respiratory rate of 48 could be triaged ESI level 2 or 3. Based on the patient's history and physical assessment, the nurse must ask if the vital signs are enough of a concern to say that the patient is high risk and cannot wait to be seen. Chapter 5 explains vital signs in detail and gives examples.

Figure 2-5. Danger Zone Vital Signs

Figure 2-5. Danger Zone Vital Signs

The box in this figure is labeled D and lists the danger zone vital Signs. An arrow pointing from the box and labeled 'No' goes to the number 3 (for triage level 3).

Temperature is only included with children under age 3. Significant fever may exclude young children from categories 4 and 5. This will help identify potentially bacteremic children and avoid sending them to a fast track setting or keeping them waiting a prolonged time. Pediatric fever guidelines are described in detail in Chapter 5.

Does Time to Treatment Influence ESI Triage Categories?

An estimate of how long the patient can wait to be seen by a physician is an important component of most triage systems. The Australasian and Canadian Triage Systems both require patients to be seen by a physician within a specific time period, based on their triage category. ESI does not mandate specific time standards in which patients must be evaluated by a physician. However, patients who meet criteria for ESI level 2 should be seen as soon as possible; it is up to the individual institution to determine specific policies for what constitutes "as soon as possible."

Frequently, there may be confusion between institutional policy and "flow or process of patient care" and ESI triage level. Examples of patient scenarios in which flow and triage category may seem to conflict are presented below.

Often trauma patients present to the triage nurse after sustaining a significant mechanism of injury, such as an unrestrained passenger in a high-speed motor vehicle crash. The patient may have left the crash scene in some way other than by ambulance and presents to triage with localized right upper quadrant pain with stable vital signs. This patient is physiologically stable, walked into the ED, and does not meet ESI level-1criteria. However, the patient is at high risk for a liver laceration and other significant trauma, so should be triaged as ESI level 2.

Frequently, EDs have trauma policies and trauma response level categorization that will require rapid initiation of care. Triage and trauma response level are both important and should be recorded as two different scores. While the triage nurse recognizes this is a physiologically stable trauma patient and correctly assigns ESI level 2, she should facilitate patient placement and trauma care as outlined by the trauma policy. The patient is probably stable for another 10 minutes and does not require immediate life-saving interventions. If the same patient presented with a blood pressure of 80 palpable, the patient would be triaged as ESI level 1 and require immediate hemodynamic, life-saving interventions.

Another example of policies that may affect triage level is triage of the patient with stable chest pain. If the patient is physiologically stable but experiencing chest pain, that is potentially an acute coronary syndrome. The patient meets ESI level-2 criteria. He or she does not require immediate life-saving interventions but is a high-risk patient. Care is timesensitive; an ECG should be performed within 10 minutes of patient arrival. Often, EDs will have a policy related to rapid initiation of an ECG. While care of these patients should be rapidly initiated, the ECG is not a life-saving intervention, it is a diagnostic procedure. If the triage nurse were to triage all chest pain patients as ESI level 1, it would be difficult to prioritize the care for true ESI level-1 patients who require immediate life-saving interventions. But the patient with chest pain who presents to triage diaphoretic, with a blood pressure of 80 palpable would meet ESI level-1 criteria.

The third example of time-sensitive care is a patient who presents with signs of an acute stroke. For example, the patient who reports left arm weakness meets the criteria for ESI level 2, and the stroke team needs to be activated immediately. Time to computed tomography (CT) completion is a quality measure that must be met. But the patient with signs of stroke that is unable to maintain an airway meets ESI level-1 criteria. The stroke team would also be activated.

Finally, a somewhat different scenario is an elderly patient who fell, may have a fractured hip, arrives by private car with family, and is in pain. The patient does not really meet ESI level-2 criteria but is very uncomfortable. The triage nurse would categorize the patient as ESI level 3 and probably place the patient in an available bed before other ESI level-3 patients. Ambulance patients may also present with a similar scenario. Arriving by ambulance is not a criterion to assign a patient ESI level 1 or 2. The ESI criteria should always be used to determine triage level without regard to method of arrival.

In general, care of ESI level-2 patients should be rapidly facilitated and the role of the charge nurse or flow manager is to know where these patients can be placed in the treatment area on arrival. All level-2 patients are still potentially very ill and require rapid initiation of care and evaluation. The triage nurse has determined that it is unsafe for these patients to wait. Patients currently may be stable, but may have a condition that can easily deteriorate; initiation of diagnostic treatment may be time sensitive (stable chest pain requires an ECG within 10 minutes of arrival); or the patient may have a potential major life or organ threat. ESI level-2 patients are still considered to be very high risk.

In the current atmosphere of ED crowding, it is not uncommon for the triage nurse to be in a situation of triaging many ESI level-2 patients with no open ED rooms in which to place the patients. In these situations, the triage nurse may be tempted to "under-triage." This can lead to serious, negative patient outcomes and an underrepresentation of the ED's overall case mix. When faced with multiple ESI level-2 patients simultaneously, the triage nurse must evaluate each patient according to the ESI algorithm. Then, the nurse can "triage" all level-2 patients to determine which patient(s) are at highest risk for deterioration, in order to facilitate patient placement based on this evaluation. For example, the patient with chest pain would be brought in before the patient with a kidney stone.


In summary, the ESI is a five-level triage system that is simple to use and divides patients by acuity and resource needs. The ESI triage algorithm is based on four key decision points. The experienced ED RN will be able to rapidly and accurately triage patients using this system.

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.

Emergency Nurses Association (2007). TraumaNnursing Core Course (Provider Manual), 6th ed. Des Plaines, IL: Emergency Nurses Association.

Tanabe P, Gimbel R, Yarnold PR, Kyriacou DN, Adams J (2004). Reliability and validity of scores on the Emergency Severity Index version 3. Acad Emerg Med 11:59-65.

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, Travers D, Gilboy N, Rosenau A, Sierzega G, Rupp V, et al (2005). Refining Emergency Severity Index triage criteria, ESI v4. Acad Emerg Med 12(6):497-501.

Travers D, Waller AE, Bowling JM, Flowers D, Tintinalli J (2002). Five-level triage system more effective than three-level in tertiary emergency department. JEN 28(5):395-400.

Wuerz R (2001). Emergency severity index triage category is associated with six-month survival. ESI triage study group. Acad Emerg Med 8(1):61-64.

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.

Wuerz R, Travers D, Gilboy N, Eitel DR, Rosenau A, Yazhari R (2001). Implementation and refinement of the emergency severity index. Acad Emerg Med 8(2):170-176.

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Current as of November 2011
Internet Citation: Emergency Severity Index (ESI) Implementation Handbook, 2012 Edition: Chapter 2. Overview of the Emergency Severity Index. November 2011. Agency for Healthcare Research and Quality, Rockville, MD.