While emergency departments are likely to encounter the first patients with pandemic influenza, many sick patients should be cared for by intensivists, so they are critical to guiding triage when demand exceeds capacity. Intensivists therefore should be part of strategic planning committees before, during, and after pandemics, to coordinate ICU response with hospital and regional efforts for triage, clinical care, and infection control.

During a large-scale pandemic, resources will become limited, even in developed nations. Multiple and context-appropriate strategies will be required to build a sustained surge capacity for mass critical care. While short-term capacity is crucial, long-term sustainability will be more important. The starting point for this in Canada is the Canadian Pandemic Influenza Plan [41]. In the USA, these include, among others, Pandemic Influenza: Preparedness, Response, and Recovery from the Department of Homeland Security [42], and the Pandemic Influenza Plan from the CDC and Department of Health and Human Services [43]. Clinicians must be adaptable when using pre-existing protocols, as they are often based on historical and non-generalizable illness syndromes and outcomes. Resource-limited countries will also need significant adaptation, likely with a greater focus on pre-hospital and transportation systems [44] (Fig. 2).

Fig. 2 a Stages of mass critical care, with various ICU response thresholds. As a pandemic progresses, resources become scarce and there is increasing strain placed on the health care system from more cases [24]. b A potential triage strategy for various patient groups as the capacity of the ICU is slowly overwhelmed to streamline admissions without the greatest opportunity for benefit from ICU level care. Transparency is paramount in this process Full size image

Treatment of severe influenza involves a combination of specific and supportive therapies. While there is limited evidence of the effectiveness of neuraminidase inhibitors in severe influenza, they are likely to be recommended for use in critically ill patients during the initial phases of pandemic influenza [41,42,43]. Pandemic influenza should also be treated according to the pathophysiological mechanism of injury. While influenza results mainly in upper and lower respiratory tract infection, secondary bacterial pneumonias, acute respiratory distress syndrome (ARDS), encephalitis, and myocarditis complicate severe illness. Many patients will require mechanical ventilation. If demand outstrips critical care capacity, a triage system will be needed in developed health systems; this already routinely occurs in resource-limited settings. Developing a pandemic-specific and responsive triage system has proven challenging even in highly resourced systems. Triage systems based upon the severity of illness scores, beyond which intensive care might be considered futile, are fraught with poor performance for individual patient decisions and were not developed involving the patients to whom the triage tool would be applied. For example, the 2009 pandemic affected young non-immune patients, many of whom had high illness severity scores; however, with intensive care, mortality was low in developed countries [45]. Modeling data suggests that to perform better than a first-come, first-served basis, the triage tool would have to have a 90% sensitivity and specificity [46]. The Ontario Health Plan for an Influenza Pandemic critical care triage protocol assembled a task force with public consultation to determine the best distribution of resources during a pandemic. Surprisingly, only “first-come, first-serve” and “random selection” principles were favored by the panel, based on a need to balance a utilitarian approach with equity considerations. They suggested that “these criteria serve as a defensible ‘fail safe’ mechanism for any triage protocol” [45] (Table 1).

Table 1 Outline of possible triage strategies during a pandemic or other emergency situation where resources are limited. Multiple task forces favor FCFS and traditional methods as the most ethical during a pandemic Full size table

Beyond mechanical ventilation, access to extracorporeal life support (e.g., ECMO) will be an even more limited, but perhaps life-saving, resource during a pandemic [47]. There may be barriers to patient transfer between institutions given infection control concerns, limiting access to treatment. Mobile units capable of setting up ECMO at peripheral sites before transfer may be preferable during a pandemic and was a successful approach used during the 2009 H1N1 pandemic [48]. While ECMO appears to be effective in the treatment of selected patients with severe ARDS [49,50,51], it relies on a smaller scale pandemic. In the event of a pandemic that overwhelmed the health care system, existing ECMO resources might be allocated using existing locally acceptable criteria, coupled with a first-come, first-served basis, understanding that in a sustained outbreak, time-limited trials of treatment represent one mechanism to effect triage.

During a severe pandemic, context-appropriate standards of care would be required if demand for resources substantially exceeds capacity. Such a crisis-based standard of care might be defined as a “substantial change in usual healthcare operations and the level of care it is possible to deliver, which is made necessary by a pervasive … or catastrophic disaster” [52]. The release of crisis standards of care would be made by the regional or national governments, through Ministries of Health or Public Health Agencies, but intensivists would reasonably be expected to be involved in this process of development. Such standards might consider (1) mechanical ventilation, (2) IV fluid resuscitation, (3) vasopressor administration, (4) sedation and analgesia, (5) antiviral treatment, and (6) therapeutics and interventions, such as renal replacement and nutrition for critically ill patients [29]. Thought should also be placed on dealing with special populations—such as children and pregnant women [30].

While providing high levels of critical care through a pandemic, we must maintain the safety and wellbeing of health care workers (HCWs). Beyond any professional obligation to HCW safety, there is also likely to be a public health benefit to this—when HCWs become sick, or fear becoming sick, they are less able to perform clinical duties. Lessons can be learned from experiences in Toronto and other major centers with SARS. Approximately 20% of cases globally were in HCWs [53]. Nosocomial amplification is a common aspect of many outbreaks. While influenza is regularly spread through contact and droplet transmission, certain procedures in hospitals—intubation, ventilation, and bronchoscopy—create potential airborne transmission. Infection control practices are essential to limiting the spread of pandemic influenza [54]. The loss of clinical personnel to illness resulted in the shutdown of most non-urgent healthcare for the entire city. Preventing this loss of capacity by protecting health care personnel is a critical element of an effective response.

Public health officials working with clinical experts must make rapid recommendations about appropriate personal protective equipment, and for novel threats, these recommendations must be updated as more information about the pandemic becomes available. Pre-pandemic simulations can play a vital role in preparing staff for these outbreaks—for infection prevention and control, for clinical care practices, and also to help staff prepare “emotionally” for stressful environments.

We can also design ICUs to limit the spread of infection. In Singapore, following SARS, the emergency room was redesigned so that febrile patients were allocated where air flow patterns did not carry to other areas of the department [55]. In Toronto after SARS, the intensive care unit at the main outbreak center was rebuilt with an entire pod of beds that could be converted into a negative pressure ward. These designs and many others will help manage the next outbreak and these factors should be considered when all new hospitals are being constructed. During a pandemic, visitors and non-essential personnel should likely be limited in hospital entry, while respecting the needs of patients and families to safely connect—either in person with appropriately supported PPE or using novel ward design and/or electronically augmented virtual connections.