The literature search, Internet searches and consultations with experts failed to identify any general triage protocols for critical care. Therefore, the working group embarked on developing a critical care triage protocol. Although triage protocols were identified for trauma17–20
and chemical, biological, radiation and nuclear events,16
these were not felt to be generalizable to the population or situations in critical care. However, certain features of these protocols (e.g., a colour-coded triage tool,21
inclusion criteria, exclusion criteria and minimum qualifications for survival16
) were deemed useful for a triage protocol for critical care. Illness severity scoring systems used to predict critical care outcomes were also assessed for potential inclusion in the protocol.22–27
The Sequential Organ Failure Assessment (SOFA) score was felt to be the most appropriate scoring system for use in a triage protocol given its basis on physiologic parameters, ease of calculation, requirement for simple laboratory tests and its validation for use in patients with a wide variety of conditions requiring critical care.22,28–31
(The scoring criteria for the SOFA score are provided in Appendix 1, available online at www.cmaj.ca/content/cgi/full/175/11/1377/DC1
.) The final protocol developed by the working group is presented in part in and in and .
Fig. 1: Prioritization tool used in triage protocol for the initial assessment of patients' needs for critical care during an influenza pandemic. See online Appendix 1 for the SOFA scoring criteria and online Appendix 2 for the complete prioritization (more ...)
The protocol is designed to provide guidance for making triage decisions during the initial days to weeks of an influenza pandemic if the critical care system is overwhelmed. The impetus for this triage protocol was the potential for the critical care system to be flooded by patients with influenza during a pandemic. However, it must be noted that the triage protocol would apply to all patients who are being considered for critical care, not just those with influenza, since all patients must share a single pool of resources.
The triage protocol has 4 main components: inclusion criteria, exclusion criteria, minimum qualifications for survival and a prioritization tool. The inclusion criteria () identify patients who may benefit from admission to critical care and primarily focus on respiratory failure, since the provision of ventilatory support is what fundamentally differentiates the ICU from other acute care areas (e.g., step-down units). It is anticipated that expanded care models will be developed as part of the surge capacity response and will permit hemodynamic support and other advanced care modalities to be provided in areas that have appropriate monitoring but do not typically provide this level of care. However, should hemodynamic support not be available elsewhere, it will qualify as an inclusion criterion for critical care admission.
The exclusion criteria () can be broken down into 3 categories: patients who have a poor prognosis despite care in an ICU, patients who require resources that simply cannot be provided during a pandemic and patients with advanced medical illnesses whose underlying illness has a poor prognosis with a high likelihood of death, even without their current concomitant critical illness. The first category reflects the “hard” boundaries that many intensivists recognize from their day-to-day care of patients,32–35
such as end-stage cancer, severe burns,36
unwitnessed or recurrent cardiac arrests39
and patients with a baseline SOFA score greater than 11, who have more than a 90% mortality.22,28
Advanced age clearly contributes to higher death rates in specific disease subsets of critically ill patients,40,41
but it may not be a strong predictor of critical care outcomes in general and therefore was not included in the original draft protocol. However, we received strong and consistent feedback from both expert and stakeholder consultations that an age criterion should be included. This remains one of the areas requiring further research and community input.
The second category of exclusion criteria includes patients who may
benefit from critical care but would require intense use of resources and prolonged care that cannot be justified during a pandemic, when the goal is to do the most for the most with the limited resources available. The third category of exclusion criteria includes patients who have high resource requirements and are likely to experience significant complications from influenza (e.g., patients with advanced cancer or immunosuppression). Others in this category are patients who have end-stage cardiac, hepatic or pulmonary failure. The cut-off marks selected here are adapted from the transplant literature42–45
and typically represent a baseline death rate higher than 50% within the next 1 to 2 years. Given that transplantation is unlikely during a pandemic, combined with the cumulative risk of death from their acute critical illness, these patients again fall into a category where considerable resources would have to be expended with a low probability of long-term survival. Many of the criteria in this third category require more detailed definitions in order to put it into practice. These were omitted for brevity but will be included in the training provided for triage officers.
The “minimum qualifications for survival” form the third component of the triage protocol. These qualifications represent a ceiling on the amount of resources that can be expended on any one person. This is a concept foreign to many medical systems in developed countries but one that has been used in war zones and refugee camps.16
The minimum qualifications for survival dictate reassessment at 48 and 120 hours, as well as an ongoing cut-off ceiling if a patient ever has a SOFA score of 11 or higher or any other exclusion criteria. The key component of the minimum qualifications for survival is the attempt to identify at an early stage patients who are not improving and who are likely to have a poor outcome. In day-to-day practice, it may take days or weeks of intensive care before this poor outcome occurs. During a pandemic, several other patients could have had their lives saved during this time.
The final component of the triage protocol is a tool for the prioritization of patients for admission to the ICU and access to ventilation (; see the complete prioritization tool in Appendix 2, available online at www.cmaj.ca/cgi/content/full/175/11/1377/DC1
). For ease of use, the familiar colour scheme (blue or black, red, yellow, green) commonly used in civilian and military disaster triage protocols was adopted. Patients in the blue (or black) category are those who fall into the expectant category and should not receive critical care. Depending on their condition and medical issues, patients may either continue to have curative medical care on a ward or palliative care. Patients in the red category have the highest priority for ICU admission and mechanical ventilation, if required. In selecting the patients for this category, the aim is to find those who are sick enough to require the resource and whose outcome will be poor if they do not receive it but are not so sick that they will not recover even if they do receive ICU care. Patients with single organ failure, particularly those with respiratory failure due to influenza who otherwise have a low SOFA score, are included in the red category assuming they have no exclusion criteria. These patients will derive the maximum benefit from ICU care and mechanical ventilation. The goal is to optimize the effectiveness of the triage protocol so that every patient who receives resources will survive. Although this is unlikely to be completely successful, it can be used as a target to guide modification of the triage protocol based on patient outcomes during a pandemic. Patients in the yellow category are those who, at baseline, are very sick and may or may not benefit from critical care. They should receive care if the resources are available but not at the expense of denying care to someone in the red category. At the reassessment points, patients who are improving are given high priority (red) for continued care, while those who are not showing signs of improvement are classified as yellow. Patients in the green category are those who should be considered for transfer out of the ICU because they are well enough to be cared for without mechanical ventilation or other ICU-specific interventions.