Center Articles and Publications

Augmentation of Hospital Critical Care Capacity after Bioterrorist Attacks or Epidemics: Recommendations of the Working Group on Emergency Mass Critical Care

Lewis Rubinson, Jennifer B. Nuzzo, Daniel S. Talmor, Tara O’Toole, Bradley R. Kramer, Thomas V. Inglesby for the Working Group on Emergency Mass Critical Care

Critical Care Medicine. 2005;33(10):2393-2403. Copyright © 2005 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins. DOI: 10.1097/01.CCM.0000173411.06574.D5

Abstract: The Working Group on Emergency Mass Critical Care was convened by the Center for Biosecurity of the  University of Pittsburgh Medical Center and the Society of Critical Care Medicine to provide recommendations to hospital and clinical leaders regarding the delivery of critical care services in the wake of a bioterrorist attack resulting in hundreds or thousands of critically ill patients. In these conditions, traditional hospital and clinical care standards in general, and critical care standards in particular, likely could no longer be  maintained, and clinical guidelines for U.S. hospitals facing these situations have not been developed. The Working Group offers recommendations for this situation.

Sections:
- Working Group Methods
- Working Group Planning Assumptions
- Working Group on Emergency Mass Critical Care: Planning assumptions and recommendations 
  (Table 1)
- Critical Care Manifestations of Category A Bioterrorist Pathogens and Toxins (Table 2)
- Working Group Recommendations
- Working group estimations of appropriate staffing ratios for routine intensive care unit (ICU) 
  conditions vs. emergency mass critical care conditions (Table 3)
- Example of medication classes necessary in emergency mass critical care conditions (Table 4)
- Necessary Future Steps
- References

The Working Group on Emergency Mass Critical Care was convened by the Center for Biosecurity of the University of Pittsburgh Medical Center and the Society of Critical Care Medicine to provide recommendations to hospital and clinical leaders regarding the delivery of critical care services in the wake of a bioterrorist attack resulting in hundreds or thousands of critically ill patients. In these conditions, traditional hospital and clinical care standards in general, and critical care standards in particular, likely could no longer be maintained, and clinical guidelines for U.S. hospitals facing these situations have not been developed. The Working Group offers recommendations for this situation.

Although the primary objective of these recommendations is to provide guidance for hospitals to deliver mass critical care after a bioattack, such guidance would be of clear value in preparing for large-scale epidemics such as pandemic influenza and SARS outbreaks of a greater magnitude than those seen in 2002–2003. The Working Group believes that an individual hospital that bases its planning efforts and emergency response actions on these recommendations might double, triple, or perhaps even further augment its overall critical care capacity. If all hospitals in a given city or region were prepared to take such actions in a crisis, a city or region might be able to substantially increase the number of critically ill patients who could be provided potentially life-saving medical care.

The Working Group believes that hospitals’ responses to bioterrorism or largescale epidemics should be coordinated regionally in whatever ways now practically feasible. Such coordination would allow efficient sharing of healtcare professionals, hospital beds, equipment, medicines, and other resources. However, the Working Group also recognizes that formal or informal regional coordination of hospital response efforts during outbreaks is not yet sufficiently advanced for meaningful functionality in the short term for many, if not most, cities or regions. The complexities of multiple-institutional planning, differing priorities, varying materials and human resources, and competition between hospitals are some of the barriers that now impede such regional coordination. So, although regional hospital coordination should be the goal for responding to mass casualty bioterror attacks, for the present, many hospitals will need to do what they can as individual or small groups of organizations to ensure their ability to deliver medical care in a crisis. These Working Group recommendations are intended to provide some guidance to hospitals for such efforts. These recommendations propose which critical care interventions should be given highest priority in these conditions, how patient triage decisions should be considered, how to make the best possible use of highly skilled medical staff, how to make the best use of a hospital’s physical assets to deliver critical care, which infection control procedures should be given top priority, and what medical equipment and classes of medications should be held in reserve in advance of such crises.

Working Group Methods

The Working Group on Emergency Mass Critical Care consists of 33 experts from fields including bioethics, biosecurity, critical care, disaster preparedness, government response, hospital administration, hospital engineering, and infection control. Staff of the Center for Biosecurity of the University of Pittsburgh Medical Center selected members of the Working Group on the basis of their expertise and experience.

The first author (LR) conducted a literature search of MEDLINE databases from January 1966 to June 2004 using the search terms bioterrorism, disaster medicine, disaster critical care, mass casualty, mass casualty critical care, and patient triage. Additional publications and information sources were identified by reviewing bibliographies and federal government bioterrorism planning documents, by participating in governmental and hospital working groups regarding hospital preparedness, and through discussions with a wide range of experts on mass casualty medical care. The initial draft of the Working Group’s recommendations was the result of the synthesis of information obtained in the evidencegathering process. The Working Group was convened at the Center for Biosecurity of UPMC in Baltimore, MD, on June 29, 2004, to review the first draft. Revisions were made in accord with oral and written comments from the Working Group. This second draft was sent to Working Group members electronically with requests for comment. The additional comments were incorporated into a third and final draft. All Working Group members supported the final recommendations.

Working Group Planning Assumptions

Current Critical Care Medical Response Capacity for Bioterrorism
The Working Group agreed on the following planning assumptions on which the recommendations of this group would be based (see Table 1 for summary).

Planning assumption: Future bioterrorist attacks may be covert and could result in hundreds, thousands, or more critically ill victims.

It is not possible to estimate the probability, size, distribution, location, or pathogen of a potential bioattack. An adversary would have the choice of time, method, and location of future attacks, and intelligence agencies may not be able to provide warning. Therefore, it is necessary that hospitals should presume they will have no advance warning of the timing, location, and character of a bioweapons attack. Although some attack scenarios may result in few victims, other attack scenarios could lead to hundreds, thousands, or more critically ill victims.^1,2 It is therefore necessary for hospitals to prepare to cope with hundreds or thousands of critically ill patients in a given city in the event of future bioterrorist attacks.

Planning assumption: Critical care will play a key role in decreasing morbidity and mortality after a bioterrorist attack.

If people are deliberately exposed to one of the many pathogens or toxins that could be used as biological weapons (such as those on the Category A list),³ critical medical illness is a likely consequence. Although modern hospital experience in treating the specific diseases caused by bioweapons agents is limited, clinical conditions associated with these illnesses—such as sepsis, acute respiratory distress syndrome, and other causes of respiratory failure—are commonly treated in intensive care units (ICUs)^4–6 (Table 2 provides examples illustrative of the clinical conditions that could follow bioterrorist attacks). Once patients develop these common lifethreatening clinical conditions, treatments that are specifically for the precipitant of critical illness (such as antibiotics for pneumonia) are beneficial (if they exist) but are generally not sufficient for survival.^7,8 “Supportive” critical care interventions, including treatments that support failing organ systems (e.g., mechanical ventilation, hemodynamic support, renal replacement therapy), are often essential for the survival of critically ill patients. When patients are offered disease- specific treatments and supportive critical care under normal ICU conditions, nearly three fourths of patients with severe sepsis⁵ and at least half of patients with septic shock or acute respiratory distress syndrome survive.^9–14 Whether outcomes would be similar for victims of bioterrorist attacks who develop these conditions is uncertain, but the Working Group believes a reasonable planning assumption is that supportive critical care will play an essential role in decreasing morbidity and mortality rates after a bioterrorist attack.

Planning assumption: Mass critical care cannot be provided without substantial planning and new approaches to providing critical care.

In the United States, most acute care hospitals (75%) have an ICU, with approximately 87,400 ICU beds distributed among 4,150 hospitals.¹⁵ Vacant ICU beds are in short supply.^15–17 Hospitals have existing mechanisms to compensate for small surges in the number of critically ill patients. When ICU beds are not immediately available, critically ill patients are boarded in emergency departments, other types of ICUs (e.g., medical patients can be boarded in surgical ICUs), and postanesthesia care units.^18,19 In such situations, patients already in the ICU but deemed unlikely to benefit from continued ICU care can be transferred to non-critical care hospital floors.^20,21 These initial, routine processes would (and already do) allow hospitals to offer critical care to a modest, additional number of patients if necessary. If additional capacity were needed, elective surgeries could be cancelled and hospital discharges could be expedited to make additional space for patients being transferred out of ICUs. Staff could be recalled to the hospital, vacations cancelled, and shifts extended.²² The Working Group judges that these early-stage critical care augmentation strategies might allow hospitals to expand their ICU capacity by 20–50%, while still offering usual (or near usual) standards of critical care medicine. Such activities, however, will not be sufficient to respond to crises during which the number of critically ill patients is >100–500% beyond a hospital’s or an entire metropolitan area’s normal ICU capacity.

Planning assumption: A hospital would have limited ability to divert or transfer patients to other hospitals in the aftermath of a bioterrorist attack.

Given that people infected by biological weapons may not show symptoms for days or weeks after exposure, they are likely to seek care at a number of different hospitals in a city or region. After a large bioterrorist attack, a number of hospitals in a local area may face simultaneous surges in critically ill patients. This would be different from the expected aftermath of conventional disasters or rapidly acting chemical exposures, where most victims are likely to be concentrated at the hospital nearest the event.^23–26 If a bioterrorist attack led to victims presenting for treatment at multiple hospitals, it might not be possible to redistribute victims to other local hospitals.

Transfer of patients to more distant areas, including to hospitals enrolled in the National Disaster Medical System, also may be difficult. Hospitals at a distance may hesitate to accept patients in transfer until they are more certain that their own local catchment area will not have its own mass casualties to care for. Even if distant hospitals are willing to make ICU beds available, the logistics of transferring large numbers of critically ill patients around the country would be formidable. There are no extant, tested mechanisms for transfers of critically ill civilians on this scale.²⁷ If the biological agent were contagious, transfer of patients would likely be further complicated by both logistic difficulties (e.g., fear of contamination of aircraft or flight crews) and concerns about minimizing the spread of the contagion.²⁸ Therefore, at present, hospitals should not assume that transferring patients to other local or distant hospitals will allow them to cope with increased numbers of critically ill patients during a biological attack.

Planning assumption: Currently deployable medical teams of the federal government would have a limited role in increasing a hospital’s immediate ability to provide critical care to large numbers of victims of a bioterrorist attack.

In the aftermath of a large bioterrorist attack, states might formally request federal assistance. Therefore, hospitals should know the point of contact in the state government for emergency assistance. According to the National Response Plan, the Department of Health and Human Services is the lead agency for federal aspects of the medical response for civilian disasters and is directed to work in collaboration with a number of additional federal agencies.²⁹ The combined efforts of these agencies can achieve a number of medical functions, but there is no specific federal team or response system ready to provide critical care to large numbers of civilian victims of a terrorist attack in the first 24–48 hrs after recognition of such an event. Disaster Medical Assistance Teams were developed to provide federal medical assistance to local communities during a conventional disaster, and they have successfully responded by providing trauma support in a number of events.³⁰ National Medical Response Teams are similar to Disaster Medical Assistance Teams, although they have additional training and equipment for responses to chemical, nuclear, and biological agent releases. In addition, 3,900 commissioned officers of the U.S. Public Health Service are rostered with the Office of Force Readiness and Deployment to provide assistance in a disaster situation. But Disaster Medical Assistance Teams, National Medical Response Teams, and the U.S. Public Health Service Corps were not designed to increase inpatient critical care capacity, and they do not have enough specialized medical staff or equipment to substantially increase a hospital’s ability to provide mass critical care, especially if multiple hospitals are simultaneously in crisis. The current utility of the newly initiated program establishing Federal Medical Contigency Stations for augmenting critical care capacity remains uncertain. A number of critical care-related professional societies maintain lists of potential volunteers who may be called on by the federal government, but it is unclear how many volunteers would help,^31,32 how fast they would arrive, what resources they would be provided, and how they would be successfully integrated into a hospital’s critical care efforts.

The U.S. Air Force has a program called the Expeditionary Medical Support System. These deployable medical treatment facilities have the ability to provide critical care, although their current ability to treat large numbers of contagious patients is limited. It is uncertain how quickly and how much additional, immediate critical care capacity the Expeditionary Medical Support System program could provide to the civilian health care system after a bioterrorist attack or how quickly it could be deployed. The U.S. Army Medical Command has an emergency management program through which it can deploy teams or resources under the National Response Plan to provide short-duration medical augmentation to civil authorities (Medical Command Regulation 525-4, United States Army Medical Command, U.S. Army December 11, 2000). Resources that may be available include medical personnel (i.e., Special Medical Augmentation Response Teams) and mobile support hospitals (U.S. Army Office of the Surgeon General, April 2004). However, competing priorities related to national defense and logistic issues, such as transportation and space requirements, could limit the availability of these resources.²⁷

Therefore, a Working Group planning assumption is that the currently deployable medical teams of the federal government would have a limited role in immediately increasing a hospital’s immediate ability to provide critical care to large numbers of victims of a bioterrorist attack.

Planning assumption: Hospitals may need to depend on nonfederal sources or reserves of medications and equipment necessary to provide critical care for at least the first 48 hrs following discovery of a bioterrorist attack.

Department of Health and Human Services reports that it can deliver “12-hr push packages” from the Strategic National Stockpile (SNS) containing vital medical equipment and medicines to state health authorities within 12 hrs of notification of release authority.^33,34 The push packages could arrive in affected cities or regions faster if they had been prepositioned for a high-risk event (e.g., national security special events). The SNS contains some of the equipment necessary to care for contagious critically ill patients (e.g., N95 respirators for airborne precautions can be provided, but fluid-impervious gowns for droplet/contact precautions cannot) and some of the medical equipment necessary to temporarily augment critical care capacity (e.g., ventilators, ventilator circuits, sedation, intravenous fluids, and vasopressors). Once the SNS Program delivers its materials to states, the states are responsible for distributing the materials. If many hospitals within a state have concurrent needs in a crisis, states will need a mechanism for prioritizing the needs of different hospitals. If multiple states have concurrent stockpile needs, Department of Health and Human Services and Centers for Disease Control and Prevention would determine distribution priorities for the SNS Program. In the event of large attacks, portions of the SNS might be held in reserve to prepare for a subsequent attack. As a result of these unknowns, the Working Group is concerned that distribution issues at the local level could potentially limit the immediate usefulness of the SNS, especially in conditions of many simultaneous competing demands for resources. The Working Group also recognizes that the SNS has a component called Vendor Managed Inventory that includes large quantities of pharmaceuticals that would arrive in 24–36 hrs. The SNS can facilitate the acquisition of drugs not on the SNS formulary. Given the above, the Working Group assumes that for the present, a prudent planning assumption for hospitals is that they will need to depend largely on nonfederal sources or reserves of medications and equipment necessary to provide critical care for at least the first 48 hrs following discovery of a sizeable bioterrorist attack. The 48-hr recommendation is based on the best professional judgment of the Working Group members and is consistent with other expert-derived disaster planning recommendations.³⁵

Working Group Recommendations

Providing Critical Care for Many Victims: Modifying Usual Standards of Care
The Working Group recommends that hospitals develop a set of emergency mass critical care practices that could be implemented in the event critical care capacity of that hospital is exceeded. Hospitals should articulate in advance of such a crisis the critical care interventions that will be given the highest priority. The premise of such emergency mass critical care practices is that more lives could be saved if a circumscribed set of key critical care interventions were offered to a larger number of patients rather than if maximal critical care interventions with all their incumbent human and material resource requirements (i.e., usual U.S. standards of critical care) could only be provided only to a small number.

Hospitals should develop criteria to trigger a shift to emergency mass critical care practices. Since there would be substantial ethical, political, legal, regulatory, and logistic ramifications with adjusting standards of critical care delivery, state and possibly federal government participation would be necessary in developing these criteria. Legislative action might need to be taken in advance of such a crisis to allow hospital and health care workers to make this shift without fear of legal liability.

Hospitals in such a crisis would need to have the agility and autonomy to make a shift to emergency critical care practices on an institutional level, but it would be far more effective, clear, and fair if all hospitals in a city or region affected by such a crisis made the switch to emergency critical care practices at the same time. Criteria for declaring a critical care crisis as well as the nature of the changes in care standards ideally would be publicly discussed and transparent to hospital staff and the community before implementation during an event.³⁶

Decisions Regarding Which Critical Care Interventions Should Be Provided
Usual ICU Operations. Critically ill patients are typically treated with a number of critical care interventions. Some of these interventions have demonstrated efficacy and effectiveness, others are believed to be effective but cannot be tested for ethical reasons, still others might be helpful but remain untested, and some are probably harmful although still used in some ICUs. Many of these interventions are expensive, and a number require extensive staff resources. Despite the uncertainties of some interventions’ benefits and the tremendous expenditures of human and/or material resources, usual ICU practice standards in the United States dictate that interventions that might be useful are initiated and maintained as long as the patient or his or her surrogate decision maker wishes to continue aggressive treatment and the treating clinicians believe that such interventions might be beneficial.³⁷ As a patient becomes increasingly ill, additional resources and interventions are brought to bear, as long as these interventions are considered to offer some potential benefit to the patient. With the exception of a few very expensive or complex interventions, such individual patent care interventions are typically made with little if any consideration of the impact on the institution’s ability to provide adequate care to other ICU patients.

Emergency Mass Critical Care: Essential Elements of Critical Care. In the event that emergency mass critical care becomes necessary, shortages of specialized staff, medical equipment, and supplies could limit the number of patients who can receive the appropriate supportive critical care interventions. To increase the chance of survival for the largest number of patients during these situations, hospitals should identify essential critical care interventions and plan and prepare to maintain these essential interventions during an event. To ensure the availability of essential critical care interventions, the Working Group recommends that hospitals give priority to interventions that fulfill the following criteria: a) interventions that have been shown or are deemed by critical care experts’ best professional judgment to improve survival, and without which death is likely; b) interventions that do not require extraordinarily expensive equipment; and c) interventions that can be implemented without consuming extensive staff or hospital resources. Based on these criteria, the Working Group recommends that, at a minimum, hospitals plan to be able to deliver the following during emergency mass critical care: basic modes of mechanical ventilation, hemodynamic support, antibiotic or other disease-specific countermeasure therapy, and a small set of prophylactic interventions that are recognized to reduce the serious adverse consequences of critical illness.

Failure to provide positive pressure ventilation to critically ill patients with severe hypoxemic respiratory failure (e.g., patients with inhalational anthrax), acute respiratory distress syndrome (e.g., patients with pneumonic plague), or neuromuscular ventilatory failure (e.g., victims of botulinum toxin poisoning) will almost certainly result in death. The Working Group believes that provision of a basic mode of mechanical ventilation (e.g., assist-controlled or pressurecontrolled ventilation) for large numbers of patients should be a priority in these conditions. Mechanical ventilators in this setting need not be state of the art but should be rapidly available and portable, should provide adequate gas exchange for a range of clinical conditions that warrant mechanical ventilation, should be safe for patients (disconnect alarm capabilities), should be safe for staff (reduce staff time in patients’ rooms if disease is contagious),³⁸ and should allow for efficient use of staff. A number of ventilators on the market fulfill these criteria and cost far less than current state-of-the-art, top-of-the-line hospital ventilators.

Most hospitals have few if any “extra” ventilators available, and they have insufficient quantities of anesthesia machines to match the numbers of anticipated critically ill patients. Vendor stockpiles of ventilators in any given region are limited and are unlikely to meet local demand for many additional mechanical ventilators. The SNS currently includes thousands of portable ventilators (Puritan Bennett LP10 and Impact Eagle 754) that can be deployed. The length of time before ventilators from the SNS could be delivered to hospitals in a crisis would depend partly on the numbers of hospitals needing assistance and their geographical distribution (S. Bice, personal communication, August 19, 2004).

In the event insufficient mechanical ventilators are available to treat all patients who need ventilatory support, manual ventilation together with endotracheal tubes could be used. Studies have not demonstrated significant differences in blood gas analyses in patients ventilated manually (with volume-limiting devices) vs. those ventilated by portable ventilators during short-term transport,^39–41 and manual ventilation equipment is much cheaper than adequate mechanical ventilators. Manual ventilation may thus be a reasonable temporizing intervention, but it would require someone to be continuously manually ventilating each patient. The people who are manually ventilating patients would be at high risk for secondary transmission if the disease were contagious.³⁸ In addition, provider fatigue in extreme conditions could result in hypoventilation of the patient.

Some Working Group members advocate local, regional, or state stockpiling of limited-function mechanical ventilators. Although a few large hospitals may be able to purchase a reserve cache of these ventilators, almost no hospital can afford to purchase sufficient quantities to double or triple their usual ICU capacity. Large city, regional, or state stockpiles would help defray the cost of ventilators to a number of hospitals but would be beneficial only if state or local distribution guidelines were preestablished. Such state guidelines are currently being developed for distribution of the SNS equipment and could reduce the time required for the SNS ventilators to be sought by hospitals. The advantage of nonfederal stockpiles is that they would make additional mechanical ventilation equipment available quickly, and delivery would not be delayed as it might be if the SNS equipment was being distributed to a number of states concurrently. Working Group members who advocate nonfederal stockpiles suggest that ventilators that provide only basic modes of ventilation and are equipped for remote alarm monitoring would be sufficient (new or retired ventilators). The Working Group members all agreed that full-feature mechanical ventilators are prohibitively expensive for stockpiling at any level (federal, state, or regional).

According to national practice guidelines for septic shock, the initial priority of therapy is “to maintain a reasonable mean arterial pressure to keep the patient alive.”⁴² Intravenous fluids are recommended as initial therapy as soon as severe sepsis or septic shock is recognized.⁴³ If fluid administration fails to restore adequate blood pressure or endorgan perfusion, vasopressor therapy is then recommended.⁴² In the event of a need for emergency mass critical care, the Working Group recommends that hospitals should plan to be able to administer intravenous fluid resuscitation and vasopressor therapy to large numbers of hemodynamically unstable victims and should stockpile sufficient equipment to do this without relying on external sources for at least the first 48 hrs of the hospital medical response. Intensive monitoring of hemodynamic resuscitation end points (e.g., continuous mixed venous saturation, intra-arterial pressure, central venous pressure) is likely to be impractical during emergency mass critical care, and clinicians are likely to have to rely on simple surrogates of adequate tissue perfusion, such as systemic mean arterial pressure, neurologic function, and urine output. Decisions regarding route of administration (e.g., central venous catheter vs. peripheral venous catheter) will depend on available staff and resources.

The two major causes of death and significant morbidity in ICUs are progression of the underlying diseases that led to ICU admission and adverse consequences of critical illness and ICU care (e.g., pulmonary embolism and ventilator-associated pneumonia). In routine ICU practice, a number of critical care interventions are employed to reduce the incidence of adverse consequences. The Working Group recommends that hospitals plan to provide, during emergency mass critical care, at least two widely accepted prophylactic interventions that are used everyday in critical care: maintaining the head of a mechanically ventilated patient’s bed at 45° to prevent ventilator-associated pneumonia and thromboembolism prophylaxis.⁴⁴ A minority of Working Group members also recommend a third intervention: gastrointestinal hemorrhage prophylaxis.

Decisions Regarding Who Receives Critical Care Services
Usual ICU Operations. Critical care triage is commonly employed during everyday ICU operations;⁴⁵ both the Society of Critical Care Medicine and the American Thoracic Society have published consensus statements to guide this process.^20,21 Normally, patients who are judged to meet a subjective threshold of “likely to benefit” from critical care are admitted to and remain in ICUs on a first-come, first-served basis.²¹ Since ICU bed capacity is limited and ICU care is costly (constituting 0.6% of the U.S. gross domestic product),¹⁵ everyday triage efforts focus on avoiding unnecessary ICU admissions and transferring ICU patients to lower levels of care when they no longer require critical care services. However, these usual critical care triage processes are not intended to prioritize or arbitrate ICU admission decisions for a group of patients who all clearly will require critical care interventions, as would be the case of large bioterror attacks or in the midst of a serious epidemic.^{20, 21}

Triage in Emergency Mass Critical Care. The Working Group recommends that in the aftermath of bioterrorist attacks, if there are limited hospital resources and many critically ill patients in need, triage decisions regarding the provision of critical care should be guided by the principle of seeking to help the greatest number of people survive the crisis. This would include patients already receiving ICU care who are not casualties of an attack. Even after a hospital has shifted to delivering only essential elements of critical care to its critically ill patients, it may become the case that there may be insufficient resources to treat all seriously ill patients. The Working Group believes that the most ethical way to help the greatest number of critically ill people survive in such dire conditions is to give such interventions first to the people deemed most likely to survive. Patients should be categorized according to likelihood of survival with emergency mass critical care. Depending on how overwhelmed the hospital is, triage decision makers using these principles could be forced to withhold essential elements of critical care from the patients categorized as most likely to die. Alternatively, triage decision makers might choose to give all patients a trial of essential elements of critical care and to withdraw critical care from those who do not clinically improve after a set period of time. It is likely that most hospitals would be forced to use a combination of withholding and withdrawing of critical care in these grim conditions.

The Working Group recommends that such triage protocols be developed before such a crisis (and modified as necessary during the event). Such protocols would need to be applied in a fair and transparent process for all patients. Adequate palliative care would need to be provided for patients for whom emergency mass critical care services are withheld or withdrawn.

Triage algorithms have been designed and validated for mass casualty traumatic injuries⁴⁶ but are not designed or intended to help categorize the likelihood of survival of critically ill medical patients. Since experience in treating most diseases caused by potential bioweapons agents is limited, there are insufficient data to establish evidence-based triage protocols for these diseases. There are a number of existing severity of illness scoring systems that have been used to categorize patients by predicted hospital survival.^47,48 An ideal triage system is based on data collected at hospital admission, requires little or no laboratory testing, and has been proven to predict hospital survival for medical critically ill patients; however, such a scoring system does not currently exist. Unlike trauma, which has well-defined vital sign and clinical predictors of immediate need for intervention and likelihood of immediate survival, there are few such predictors for medical critical illness short of impending cardiac arrest. Scoring systems that have been previously validated for ICU patients are generally not used for critical care triage during usual hospital operations because their precision at prospectively predicting the futility of medical care is limited. Such scoring systems generally require data up to 24 hrs after ICU admission to be most accurate, and they require many laboratory values that may not be immediately available during such an event. They may, however, be sufficiently accurate and precise to categorize survival likelihood within broad categories (e.g., 0–33%, 34–67%, and 68–100% likelihood of survival). Therefore, in some specific emergency conditions, scoring systems might prove useful in helping with triage decisions. In the event of such a crisis, however, if new early predictors of survival are discovered, triage decisions should reflect that new knowledge. In light of these considerations, a minority of Working Group members recommend consideration of these scoring systems in trying to make judgments about triage.

Since accurate assessments of likelihood of survival are crucial in the face of overwhelming numbers of critically ill patients, ideally senior intensivists and critical care nurses would be designated to make decisions regarding when to initiate or withhold critical care services. For example, the most experienced surgeon at an Israeli hospital is responsible for triage decisions after mass casualty trauma. However, in all likelihood, critical care personnel will be in short supply in these events and will not be able to make all critical care triage decisions. In that event, physicians and nurses not trained in critical care would need to make such decisions based on the best available information (e.g., hypoxemia despite ventilation, hypotension despite initial resuscitation).

Hospitals should attempt to establish procedures for making these types of triage decisions in advance of a crisis. Ideally, such protocols should be developed on a regional basis, with input from a number of stakeholders including hospital officials, critical care experts, community members, emergency management officials, public health officials, and ethicists. Draft proposals should be well publicized to community members and revised based on the public’s recommendations and concerns. Hospitals in the region should ensure that the intent, mechanics, and ethical considerations of the proposed triage process are understood by hospital staff and the community.

Who Should Provide Critical Care
Usual ICU Operations. The complexity of caring for critically ill patients typically requires collaboration among a multidisciplinary team of pharmacists, respiratory therapists, nurses, and medical staff.¹⁷ Critical care specialists within each of these disciplines have specific professional experience, skills, and training.

The way an ICU is staffed has been shown to have a significant impact on patient outcomes. When critical care nurses are assigned more than two patients, the risk of adverse events significantly increases.^49–52 A recent metaanalysis suggested that critically ill patients have better outcomes if they receive care from intensivists compared with physicians who are not specialists in critical care.⁵³ Pharmacists’ participation on daily rounds in a medical ICU has been shown to reduce adverse drug events by 66%,⁵⁴ and pharmacists are increasingly relied on for expert advice regarding pharmaceutical interventions in ICUs.⁵⁵ Respiratory therapists provide for the maintenance and operation of airway and ventilation equipment and delivery of respiratory treatments, and their participation in critical care has been shown to improve clinical outcomes.⁵⁶ Unfortunately, even for usual ICU operations, many of these critical care specialists are in short supply.^{57, 58}

For this article, the term intensivist is meant by the Working Group to refer to a clinician who can competently manage all of the American College of Critical Care Medicine competencies¹⁷ (including advanced airway management and capability to independently manage hemodynamically unstable or mechanically ventilated patients) and does not require critical care fellowship training or board certification.

Staffing for Emergency Mass Critical Care. In the event of a need for emergency mass critical care, there will be a sharp increase in need for intensivists, nurses, pharmacists, and respiratory therapists. Currently many hospitals have plans to cancel staff vacations and modify clinical schedules during a disaster. To encourage staff to remain at and return to work for emergencies, some hospitals have made provisions to care for staff members’ families and pets. In addition, hospitals could reassign medically trained personnel who have nonclinical responsibilities to clinical work. If additional staff are needed, emergency credentialing mechanisms for medically trained volunteers and memoranda of understanding among facilities that share clinical staff also could increase numbers. In some parts of the country, local and state agencies as well as medical professional societies are assembling volunteer registries that include retired medical personnel for deployment during a disaster. Such changes would certainly provide more clinical staff to respond to the crisis, but it is unclear whether these measures would provide much increase in the number of clinical staff with adequate critical care training and skills. During a contagious disease outbreak, it is possible that many of those health care workers who might have provided assistance would not volunteer for fear of becoming infected themselves or of endangering their family members.³¹

In the event that emergency mass critical care needs in a hospital cannot be met by intensivists and critical care nurses, the Working Group recommends modifying usual ICU staffing to incorporate nonintensivist clinicians and noncritical care nurses, using a two-tiered staffing model. In this staffing modification, termed here two-tiered staffing, nonintensivist clinicians would be responsible for general medical management of critically ill patients. Intensivists would be responsible for managing acute emergencies (e.g., airway management, hypoxemia) and ventilator parameters (in collaboration with respiratory therapists) and for providing critical care guidance to the larger group of nonintensivists. Since there are no universal standards for clinician, pharmacist, and respiratory therapist staffing in normal ICU operations, the Working Group developed estimates of numbers of staff required to provide standard critical care for every 12 ICU patients cared for during a 24-hr period.⁵⁹ Using these estimates of standard ICU staffing as a baseline, the Working Group made recommendations regarding how to modify critical care staffing in the event of a crisis (Table 3).

Using these principles, the Working Group recommends that in emergency mass critical care settings when there are inadequate numbers of intensivists, hospitals should plan for nonintensivists to manage approximately six critically ill patients and to have intensivists coordinate the efforts of up to four nonintensivists.

The Working Group recognizes that large bioattacks could result in such a high number of critically ill patients that patient-provider ratios would need to be further increased.

Hospitals should develop preprinted clinician order forms for such crises to reduce medical errors and improve standardization of medical care. These order forms should reflect the protocols for general delivery of emergency mass critical care (e.g., thromboembolic prophylaxis, maintaining elevation of the head of the bed for mechanically ventilated patients); additional order sets specific to treating the disease can be developed during the crisis.

In the setting of emergency mass critical care, if a hospital has insufficient numbers of critical care nurses to appropriately manage patients, the Working Group recommends that non-critical care nurses be assigned primary responsibility for patient assessment, nursing care documentation, administration of medications, and bedside care (e.g., head of bed at 45°, moving patient to prevent pressure ulcers) and that critical care nurses advise non-critical care nurses on critical care issues such as vasopressor and sedation administration. If possible, a noncritical care nurse should be assigned to no more than two critically ill patients, and up to three non-critical care nurses may work in collaboration with one critical care nurse.

Since many nonintensivists and noncritical care nurses may not be familiar with drugs usually prescribed for critically ill patients, pharmacist participation in patient care would be highly beneficial in these emergency conditions. The Working Group believes that two-tiered staffing of pharmacists (using those who work in general hospital and outpatient pharmacies) and of respiratory therapists (using therapists who work in pulmonary function labs and other non-ICU locations) might also be possible and useful depending on a specific hospital’s staff composition.

The Working Group recognizes that a full range of hospital personnel are crucial for hospital functioning during a crisis (e.g., environmental services, facilities management, food service, and security), but staffing recommendations for these critical operations are beyond the scope of this article.

The Working Group recommends that bioterrorism training for nonintensivists, non-critical care nurses, non-critical care pharmacists, and non-ICU-based respiratory therapists should include basic principles of critical care management. One example of such training is the Society of Critical Care Medicine’s Hospital Mass Casualty Disaster Management course. This is a two-day course intended to prepare noncritical care healthcare professionals to manage critically ill patients collaboratively during mass casualty events.

The Working Group members believe that hospitals must place a top priority on the safety of a hospital’s health care workers. The Working Group members who were directly involved with the SARS response in Canada stressed that hospitals must protect health care workers and their families’ physical, mental, and financial well-being. If the disease were contagious and personal protective equipment (PPE) for health care workers were required, shift length (which some would want to lengthen due to staffing shortages) would probably need to be shortened because of the additional emotional and physical burdens of patient care. In the aftermath of a bioterrorist attack, hospital leaders would need to communicate frequently with health care workers about their concerns. If health care workers or their families perceive a lack of commitment to their well-being by the hospital, the institution might soon lose the support of its staff.

   
Infection Control for Emergency Mass Critical Care
Patients who are critically ill with a contagious disease pose special risks to health care workers because additional staff contact is required to manage critical illness and the frequent need for invasive interventions may increase the risk of secondary transmission. The 2003 SARS outbreak in Toronto demonstrated that in hospital areas where critical care was provided, there was a high risk for secondary transmission of contagious diseases to health care workers and other patients.^38,60–62 Nosocomial transmission in ICUs during the SARS outbreak in Toronto lead to the closing of 73 ICU beds—38% of the city’s tertiary hospital ICU beds and 33% of community hospital ICU beds.⁶¹ Failure to control secondary transmission may be the most important threat to a hospital’s ability to continue to provide medical care.

The implementation of and strict adherence to infection control practices have successfully curtailed nosocomial transmission during a number of outbreaks, including SARS. However, there is concern that diseases that can spread through airborne droplet nuclei (e.g., smallpox, influenza, and the agents of viral hemorrhagic fevers)^63,64 will require more serious environmental controls than hospitals have planned for and on a scale far greater than what is now possible in most facilities. The number of airborne infection isolation (AII) rooms (i.e., negative pressure with respect to the hospital corridor, undergo >6 air changes per hour, and have air exhausted directly to the outside or recirculated through high-efficiency particulate air filtration)⁶⁵ is limited in most hospitals, and hospitals cannot afford to build permanent reserve AII capacity to be used only in the event of contagious disease emergencies. As demonstrated during the SARS outbreak, however, available engineering mechanisms could be used to rapidly convert hospital rooms to negative pressure once a contagious disease epidemic demanded it.^66–68 Such practices will be more successfully instituted if engineering staff have considered logistics required for the conversions before the event. The Working Group recommends that hospitals develop preevent plans to augment usual or modified AII capacity for critically ill victims of a bioattack with a contagious pathogen.

Environmental controls are important aspects of infection control, but health care workers’ adherence to personal protective equipment (PPE) protocols is likely to be the most important determinant of control of contagion within hospitals. Even in AII rooms, health care workers can get ill from contagious patients if they do not use their PPE properly. Most of the contagious bioweapon agents are readily transmitted through contact and droplet transmission (including smallpox and viral hemorrhagic fevers) where barrier protection for health care workers is essential. Health care workers caring for patients with these or other contagious diseases with high morbidity or mortality rates must be familiar with the proper use of PPE (including how to remove without self-contaminating).^64,69–71 Although fluid-impervious gowns, respiratory protection, gloves, and face shields are used routinely in hospitals for everyday operations, the quantity of PPE that would be necessary for respiratory (airborne or droplet) and contact (especially with fomite transmission) precautions in the event of mass critical care delivery in a contagious disease epidemic would be far in excess of routine.⁷² For example, during the SARS outbreak in 2003, Sunnybrook Hospital in Ontario consumed 18,000 N95 masks per day.⁷³ Shortages of PPE may harm staff, and hospitals could cease to function during an outbreak without adequate supplies of PPE. A gross approximation of PPE quantities that might be needed in this event has been published recently.⁷²

The Working Group recommends that hospitals stockpile enough PPE to care for mass casualties of a bioterrorist attack for up to 48 hrs. All hospital clinical staff should receive training on principles of health care delivery using PPE; such training would improve normal clinical practice and emergency clinical practice for these conditions. The Society for Healthcare Epidemiology of America offers many courses on infection control.

Where Emergency Mass Critical Care Should Be Located
The Working Group recommends that, when traditional critical care capacity is full, additional critically ill patients receive care in non-ICU hospital rooms that are concentrated on specific hospital wards or unit. In the event that all ICU beds and other critical care bed options (postanesthesia care unit, emergency department, etc.) are full, areas of the hospital not usually used to deliver critical care would need to be used to provide care for the additional critically ill patients. In this setting, areas of the hospital that already contain medical equipment similar to ICUs (e.g., endoscopy and surgical suites) would be good locations to provide critical care, but in most hospitals these areas would add only a small number of critical care beds and would require cessation of the services usually provided in these areas. Concentrating critically ill patients in specific locations on specific hospital floors would help optimize implementation of the necessary infection control processes (e.g., development of additional AII or, at a minimum, negative pressure capabilities, control of who enters and leaves areas with contagious patients) and allow for efficient interaction between intensivists and nonintensivists involved in critical care delivery.⁷⁴ Ideally, advanced care hospital floors (such as step-down units and those with telemetry capabilities) should be prioritized for emergency mass critical care, since these hospital floors have many design features and patient monitoring capabilities similar to ICUs. If needed, general hospital rooms also could be used to provide emergency mass critical care.

To double or triple the ICU capacity of a hospital, approximately 20% of total hospital rooms would need to be used for provision of emergency mass critical care (ICU beds are usually <15% of total hospital beds).¹⁵ This number of hospital beds has been made rapidly available for victims of past disasters.²² If patients with traditional inpatient needs exceed available hospital beds, some emergency planners have advocated caring for patients in alternative care facilities outside of hospitals.²² Such facilities might be configured to safely provide non-critical medical care but would likely not be effective or safe facilities for providing critical care given the complexities, expertise, and specific material resources required (e.g., necessary medical gases).

The Working Group recommends that hospitals plan to be able to measure oxygen saturation, temperature, blood pressure, and urine output for the victims of bioattacks in emergency mass critical care conditions. This equipment is generally available in many parts of the hospital, and it would allow for monitoring of the most important physiologic variables in this setting. Patients on mechanical ventilators need frequent monitoring for changes in their respiratory status (e.g., need for airway suctioning, accidental disconnection from the ventilator, accidental self-extubation, barotrauma, patient-ventilator dysynchrony). Remote monitoring capabilities (e.g., ventilator alarms, oxygen saturation, and blood pressure) would be useful to maximize the efficiency of limited numbers of staff and to allow health care workers to minimize time in direct contact with highly contagious pathogens.³⁸

Learning During Emergency Mass Critical Care
In the aftermath of a bioterrorist attack, new information will have been learned about the course of illness, predictors of mortality and survival, and the efficacy and safety of new treatment strategies. Also, as evidenced by the 2001 inhalational anthrax cases and SARS, a number of unproven treatments that may have theoretical benefits are likely to be used. Rapid analyses of outcomes will help reinforce effective treatments and reduce harm for subsequent patients by limiting harmful or ineffective treatments. Currently, few hospitals have information technology and staff capabilities to collect and rapidly analyze patient data for near-real-time learning during an outbreak. The Working Group recommends that hospitals plan to use information technology tools to analyze clinical data of patients receiving care in this setting and to quickly share new observations with a broader clinical community.

Medications for Emergency Mass Critical Care
Clinical guidelines for medications that would be necessary in the aftermath of a bioterrorist attack have focused on disease-specific antimicrobial agents.⁷⁵ These interventions clearly may be beneficial for treating ill patients after a bioterrorism attack, but critically ill patients would require a wider range of medications (e.g., sedatives, vasopressors, etc.). Hospital pharmacies typically maintain varied reserves of drugs based on factors including frequency of use, cost, shelf life, and available storage space. Dozens of different drug classes and hundreds of individual drugs may be used in an ICU during usual operations, but only a small number of drugs would be critical in emergency conditions. The Working Group recommends that hospitals stockpile drugs that they deem necessary for the care of critically ill patients for up to 48 hrs into a crisis using selection criteria that include likelihood that the drug would be required for care of most patients, proven or generally accepted efficacy by most practitioners, cost, ease of administration, ability to rotate into the hospital’s formulary before expiration, and resources required for medication storage. An example of such a list is presented in Table 4. Hospitals might decide in advance that it is more cost-effective and logistically feasible to purchase such medications in cooperation with other hospitals.

IDSA, Infectious Diseases Society of America; ATS, American Thoracic Society; CAP, community-acquired pneumonia.

Necessary Future Steps

The Working Group recognizes that these recommendations are a beginning of what will necessarily be a long-term strategic effort to prepare hospitals and communities to provide critical care to victims of mass casualty terrorist attacks or large-scale disease epidemics. To implement these recommendations and to take additional steps will require the commitment of leaders and practitioners in hospitals as well as state and federal government. The Working Group believes there are particular areas of future endeavor related to mass casualty critical care that should receive special attention:

• Regional planning among hospitals and between hospitals and state agencies intended to share personnel, patient loads, medicines, and medical equipment
• Development of clear expectations regarding what the federal government can and cannot deliver to hospitals in such crises (and how quickly and in what quantity)
• Development of transparent criteria for allocating scarce medical resources in a community in crisis as a collaborative effort between government, hospital, community, and ethical leaders
• Information technology strategy for ensuring hospitals have information technology tools they need to manage and survive large-scale crises
• The legislative remedies necessary for hospitals, clinicians, and nurses to be able to operate under these unprecedented emergency conditions.

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