1. Introduction and Background

Canadian Emergency Department Triage and Acuity Scale Implementation Guidelines

• Operational objectives
• Fractile responses
• Time objectives
• Assigning the triage level
• Changing the triage level

What is Triage and why do we do it? What is a Triage and Acuity Scale? Is that something different? Triage in the simplest term is the sorting or prioritizing of items (clients, patients, tasks...). Some form of triaging has been in place, formally or informally since the first ED opened. In some instances Triage occurs at registration and in others specifically trained health care providers perform it after registration.

Efficient management of an ED requires a team of providers capable of correctly identifying patients’ needs, setting priorities and implementing appropriate treatment, investigation and disposition. As needs or expectations for rapid access to care change, EDs are frequently challenged to do more for the “system” than they have either been structurally designed for or have been staffed or equipped to accomplish.

The Canadian ED triage and acuity instrument attempts to more accurately define patients needs for timely care and to allow EDs to evaluate their acuity level, resource needs and performance against certain operating “objectives.” Three important concepts are included in the design of this scale: 1) Utility; 2) Relevance and 3) Validity.

The Canadian ED Triage and Acuity Scale is based on establishing a relationship between a group of sentinel events which are defined by the ICD9CM diagnosis at discharge from the ED (or from an inpatient data base) and the “usual” way patients with these conditions present. Each hospital could “build” their own unique usual presentations based on their own data. A community’s demographics, cultural differences, disease patterns or other available resources (walk in clinics, type of ambulance service...) will have a small influence on the usual presentation, but will have a larger effect on the proportion of patients in the different triage levels (case mix).

The mix of patients in each triage and acuity level will be the fingerprint of that ED and is expected to be nearly identical to other hospitals of similar size and designation. What may vary is the ability to achieve the time objectives as a result of available resources, efficiency of system design (computerization, bed numbers, room size, physical layout, and appropriate equipment) consistency of provider care (use of guidelines/protocols) or overcrowding (inability to transfer patients).

Operational objectives

The primary operational objective of the triage scale is related to the time to see a physician. This is because most decisions about investigation and initiation of treatment do not occur until the physician either sees the patient, or has the preliminary results necessary to recommend a course of action.

The time responses are ideals (objectives) not established care standards. These are based on a patient focus (what most of us would want for family members or ourselves) and the need for timely intervention to improve outcome (endotracheal intubation for respiratory failure, defibrillation for cardiac arrest, thrombolysis for AMI, bronchodilators for acute severe asthma).

Since it is access to appropriate care not simply physician assessment, the time from triage to see a physician is not a strict requirement and may change based on the introduction of delegated care plans or verbal review with physicians.

In recognition of wide variations in demand for care and that “ideals” cannot always be achieved without unlimited resources, each triage level is given a “fractile” response objective. This would mean that even though a Level II patient should be seen within 15 minutes it may only occur 95% of the time. While many Level II patients would be seen within 0–5 minutes occasionally it might be over 30 minutes and still be in compliance with the fractile response objective. There are many practical reasons for this: If more than one Level I patient arrived at the same time or 2 or more Level II patients arrived simultaneously. Although Level V patients have been given a time response objective of 2 hours, the fractile of 80% means that patients may wait over 6 hours on occasion.

Fractile responses

The fractile response is a way of describing how often a system operates within its stated objectives. A “fractile response” is the proportion of patient visits for a given triage level where the patients were seen within the CTAS time frame defined for that level. For example if 85% of Level III patients were seen by the physician within 30 minutes in the previous month, then the fractile response for that institution over that time period would be “85%.”

Fractile response does not deal with whether the absolute delay for an individual is reasonable or acceptable.

The fractile response data can be used in a number of ways. Frequent overuse of operating objectives implies a need for changes in the process of care, system design or sometimes reconsideration of the validity of the objective.

Time objectives

Before deciding on the validity of time objectives based on local experience it must be understood that important differences in patient outcome may only be detected in studies that evaluate the treatment advantage in very large samples. There is a need for more research on the effect time delays have on patient outcomes.

Assigning the triage level

While triage assignment is based on the “usual presentation” this is not totally dictated by the presenting complaint. The care provider’s experience/intuition (does the patient look sick?) and other information that helps to quantitate severity (vital signs, PEFR, O2 saturation, or symptoms: pain scales, associated symptoms) can also modify the triage decision. There are several diagnoses that appear in III–IV triage levels (head injury, asthma, respiratory symptoms, chest pain, and psychiatric disorders...). This is a reflection of the fact that the severity of symptoms (or presence of associated signs or symptoms such as visceral chest pain with typical associated symptoms) and risk (age, sex, past history, co-morbidity) change the probability of sentinel events and the need for rapid intervention. As care plans, guidelines and protocols are introduced the assignment of triage level is expected to become more objective and less open to debate.

Changing the triage level

To prevent unfair or unsafe “bumping” of patients with lower triage scores, it is reasonable to upgrade the triage level if the time response objective has not been met. For example, if a Level V patient has waited 2 hours that patient would then be advanced to Level IV. This is important because patient’s status can change while in the ED and the rules will not always accurately separate levels III, IV and V. Electronic tracking systems are especially suited to this type of operational change to the triage scale. For data reporting patient acuity can be determined using a combination of triage level, final diagnosis, information about procedures and length of stay (LOS).