ESI Triage Levels 1–5: Criteria, Algorithm, Chart, Vital Signs, and Examples

ESI Triage Levels 1–5:

• What are ESI Triage Levels 1–5?
• Criteria
• Algorithm
• Chart
• Vital Signs
• Examples

What are ESI Triage Levels 1–5?

The Emergency Severity Index (ESI) is a five-level triage system used in emergency departments (EDs) to prioritize patients based on the urgency of their condition and the resources they will likely need. It is designed to quickly identify patients who require immediate life-saving intervention and to streamline patient flow through emergency services. The system is both acuity- and resource-based, helping healthcare providers balance clinical urgency with departmental efficiency.

The ESI triage scale ranges from Level 1 (most urgent) to Level 5 (least urgent). ESI levels are assigned after an initial assessment of the patient’s presentation, vital signs, and expected need for diagnostic or therapeutic interventions. This structured approach allows ED staff to ensure that critical patients are treated immediately while less severe cases are managed appropriately according to available resources.

Criteria

Each ESI level is defined by specific criteria that assess patient condition and resource needs:

• ESI Level 1: Immediate life-saving intervention required (e.g., cardiac arrest, severe respiratory distress, unresponsive).
• ESI Level 2: High-risk situation, severe pain/distress, or altered mental status — must be seen quickly but not immediately life-threatening.
• ESI Level 3: Stable patient but requires two or more resources (e.g., lab tests, imaging, IV fluids, or procedures).
• ESI Level 4: Stable and needs only one resource (e.g., wound care, simple X-ray).
• ESI Level 5: Stable and requires no resources beyond physical examination (e.g., medication refill, minor rash).

“Resources” in ESI refer to any diagnostic or treatment services beyond basic history-taking and examination, such as laboratory tests, imaging, procedures, or specialist consultation.

Algorithm

The ESI Algorithm is a stepwise flowchart used to determine triage levels systematically. The triage nurse first assesses whether the patient needs an immediate life-saving intervention — if yes, the patient is Level 1. If not, the next step evaluates whether the patient is in a high-risk situation or appears acutely ill — if yes, Level 2.

If neither applies, the triage process moves to estimating how many resources the patient will require. The nurse then considers vital signs to confirm if the patient’s condition warrants a higher priority. The algorithm helps standardize decisions across different clinicians and institutions, improving safety and efficiency. It is especially valuable in high-volume emergency departments where rapid, consistent triage decisions are crucial.

Chart

Below is a simplified ESI Level Chart summarizing patient categories, urgency, and resource use:

ESI Level	Urgency	Criteria	Examples
Level 1	Immediate	Requires life-saving intervention	Cardiac arrest, severe respiratory failure, major trauma with unresponsiveness
Level 2	Emergent	High-risk, confused, severe pain or distress	Chest pain, suicidal ideation, stroke symptoms, new confusion
Level 3	Urgent	Needs ≥2 resources, stable vitals	Abdominal pain with labs and imaging, dehydration needing IV fluids
Level 4	Less Urgent	Needs 1 resource	Minor fracture requiring X-ray, wound care
Level 5	Non-Urgent	No resources needed	Prescription refill, sore throat, simple rash

This table helps quickly classify patients at a glance, ensuring consistent triage across different healthcare providers and settings.

Vital Signs

Vital signs play a crucial role in determining whether a patient’s triage level should be upgraded. After assigning a preliminary level based on resources, the triage nurse checks vital parameters such as heart rate, respiratory rate, temperature, oxygen saturation, and blood pressure. If any vital sign is significantly abnormal — for example, tachycardia above 100–110 bpm or hypotension — the patient’s triage level may be adjusted upward.

The ESI guidelines recommend using age-adjusted vital sign thresholds to identify instability. For pediatric patients, the acceptable heart and respiratory rate ranges differ, and fever thresholds are considered separately. The inclusion of vital signs ensures that resource-based triage decisions do not overlook physiologic distress or evolving critical conditions.

Examples

Here are some clinical examples illustrating how ESI levels are assigned:

• ESI Level 1: A 58-year-old male in cardiac arrest, pulseless and apneic — requires CPR and defibrillation.
• ESI Level 2: A 45-year-old female with acute chest pain radiating to the left arm, diaphoretic — high-risk, must be seen immediately.
• ESI Level 3: A 22-year-old with abdominal pain requiring labs, IV fluids, and ultrasound — needs multiple resources, stable vitals.
• ESI Level 4: A 34-year-old with an ankle sprain needing only an X-ray — one resource required.
• ESI Level 5: A 29-year-old requesting a prescription refill for hypertension — no resources required.

These examples demonstrate how ESI triage levels help standardize patient prioritization in busy emergency departments. By integrating clinical judgment, resource assessment, and vital signs, the ESI model supports efficient, safe, and evidence-based emergency care.