key: cord-0705155-ljx13yd6
authors: Adhikari, Neill KJ; Fowler, Robert A; Bhagwanjee, Satish; Rubenfeld, Gordon D
title: Critical care and the global burden of critical illness in adults
date: 2010-10-11
journal: Lancet
DOI: 10.1016/s0140-6736(10)60446-1
sha: db8ef4305cc9af4691ea97841ce28f5236b823e6
doc_id: 705155
cord_uid: ljx13yd6

Critical care has evolved from treatment of poliomyelitis victims with respiratory failure in an intensive care unit to treatment of severely ill patients irrespective of location or specific technology. Population-based studies in the developed world suggest that the burden of critical illness is higher than generally appreciated and will increase as the population ages. Critical care capacity has long been needed in the developing world, and efforts to improve the care of the critically ill in these settings are starting to occur. Expansion of critical care to handle the consequences of an ageing population, natural disasters, conflict, inadequate primary care, and higher-risk medical therapies will be challenged by high costs at a time of economic constraint. To meet this challenge, investigators in this discipline will need to measure the global burden of critical illness and available critical-care resources, and develop both preventive and therapeutic interventions that are generalisable across countries.

Critical care or intensive care medicine is often thought to have begun in 1953 when Danish patients with poliomyelitis received invasive mechanical ventilation, 1 although areas of some hospitals had been designated for patients recovering from anaesthesia or traumatic injuries a century earlier. 2 The high mortality associated with negative-pressure ventilation for the poliomyelitis epidemic in the 1950s prompted the development of hand-delivered positive-pressure ventilation via tracheostomy. These patients received care in a common location with intensifi ed nursing support and manual ventilation provided by students, and mortality declined. Intensive care units (ICUs) subsequently became a crucial component of hospital care.

Expansion of ICUs has followed advances in understanding the pathophysiology of dysfunctional organs (including lungs, heart, kidney, liver, and brain) and concomitant innovations in supportive technology. Examples of monitoring devices are central venous, pulmonary artery, and intracranial pressure catheters. Examples of organ support are mechanical ventilation for respiratory dysfunction; inotropes, vasopressors, intra-aortic balloon counterpulsation for cardiac dysfunction; dialysis for renal dysfunction; and hypothermia for brain protection after cardiac arrest. The effi cacy of some organ support technologies is generally accepted on physiological grounds. For example, we assume that patients with septic shock or acute respiratory failure who do not receive vasopressors or mechanical ventilation will die. However, the application of some technologies in specifi c clinical situations continues to be studied-for example, mechanical ventilation in acute lung injury 3 and pulmonary arterial catheterisation in critical illness. 4 Unlike other specialties of medicine defi ned by organ system, disease process, or procedure, critical care has always been challenged to establish its identity. 5 New defi nitions have tried to broaden the focus of critical care to include the patient's complexity of illness, severity of organ dysfunction, and risk of imminent death, irrespective of physical location. Although patients with critical illness in this broad sense might be found throughout hospitals, many receive care in an ICU. Patients in an ICU generally fall into three main categories: those with acute organ dysfunction (including those whose ultimate outcome is unclear and thus receive long-term intensive organ support), those who have undergone a major procedure and are monitored in the peri-intervention period to prevent and detect acute organ dysfunction, and those whose trial of intensive care has failed and are receiving end-of-life care. Intensive care is delivered by an interdisciplinary team that includes not only nurses and physicians, but also respiratory therapists, physical and occupational therapists, biotechnicians, pharmacists, nutritionists, social workers, and spiritual care providers. The daily practice of intensive care requires three related activities. First, clinicians have to simultaneously resuscitate, diagnose, and provide defi nitive care for acutely sick patients on a rapidly deteriorating but potentially reversible path towards organ dysfunction and death. Second, they have to prevent, recognise, and treat complications of treatments to support failing organs. Finally, clinicians' greatest challenge is to engage in decisions about the appropriate extent of life-supporting therapies for patients whose immediate death has been averted, but whose likelihood of returning to a meaningful survival is poor.

Intensive care medicine and nursing are young specialties, since ICUs were uncommon before the 1970s.

We searched for relevant studies published after 1999 in Medline using the MeSH terms "critical illness", "respiratory distress syndrome/adult", and "sepsis", limited to the subheading epidemiology and to adults. We supplemented the search with personal fi les.

Organisational details of ICUs continue to be debated. For example, some jurisdictions subdivide ICUs into those that provide full organ support, and intermediate units, which provide some support and monitoring to patients at risk of further deterioration. In another example, ICUs were initially separated into surgical units treating postoperative patients and medical units treating non-operative patients. Subsequently, specialty-specifi c units were developed for patients with traumatic injuries or burns, or who had undergone neurosurgery, cardiac surgery, or solid organ transplantation. Although specialty ICUs might improve outcomes by reduction of practice variability and use of specialist nursing skills, US observational data suggest that risk-adjusted mortality is similar for patients treated in general ICUs and specialty ICUs, but might be worse when patients are looked after in specialty ICUs with less experience in their illness. 6 Intensive care physician training has developed, with substantial general variation in the duration, content, assessment, and offi cial recognition of training. 7, 8 Although some regions are developing competency-based assessment models, the optimum model for training and assessment of intensivists is not clear. 9 From an academic perspective, the fi rst issue of the journal Critical Care Medicine was published in 1973 and Intensive Care Medicine in 1975; nowadays, many journals and yearly scientifi c meetings report and present advances in the care of critically ill patients.

A detailed picture of the global burden of various diseases, including cancer, cardiovascular disease, tuberculosis and HIV/AIDS, is available from web-based resources such as WHO's Global Health Observatory. However, no reliable international comparative epidemiological data of critical illness syndromes such as acute lung injury, sepsis, and multiple-organ dysfunction are available because of several fundamental challenges. First, critical illness syndromes cannot be diagnosed with one test, unlike HIV with serology or malaria with blood smears. Defi nitions for sepsis, 10 nosocomial infections, 11 and acute lung injury 12 are based on clinical, laboratory, radiological, and physiological criteria, derived by consensus panels, and under continual debate and revision. Independent of the defi nitions' validity is their absence of reliability, 13, 14 which makes comparative epidemiology challenging. Second, compared with chronic diseases like cancer, asthma, and tuberculosis, critical illness syndromes have a brief prodrome and high short-term mortality, which could be especially high in countries with few ICU resources. Such short time spans reduce the number of prevalent cases available for study at any given time, relative to chronic diseases. Third, critical illness is harder to study with existing administrative databases 15 than are trauma or cardiovascular disease because it is not defi ned by a procedure or accurately captured by hospital coding. Finally, the epidemiology of critical illness and ICU resources is dependent on the availability and intensity of other health services. Even mortality after critical illness is related to a complex interplay between a clinical decision to limit intensive care and the consequences of the disease. 16 Countries with the resources to provide organ transplantation, intensive chemotherapy for cancer, and surgery for cardiovascular disease in elderly patients with comorbid illness will have a higher burden of critical illness associated with these disorders and treatments than will those that do not have these resources. Although there is agreement that critical illness occurs outside the ICU, research on critical illness, particularly 25 and severe sepsis, 24 extrapolated to other regions based on population. These estimates are for illustration purposes only and assume that those other regions have similar intensive care capacity, underlying risk factors for the outcomes listed, and age-distributions and sex-distributions to North America. These numbers can best be interpreted as the burden of critical illness given capacity and population similar to North America. 19 and end-of-life care, 20 and have been used to generate illness severity scores. 21 These studies were done in ICUs by use of period prevalence data collection over short periods (snapshot data). Although the studies' results show process and outcome diff erences within and between countries, they do not provide accurate population-based incidence data, because there is no population denominator or complete case ascertainment within geographical regions. With a few exceptions, 22 these studies have not included data from the developing world. As a prototype critical illness syndrome, observational studies of sepsis show these epidemiological challenges. Incidence, prevalence, and prognosis are dependent on whether the study design considers measurement of population-based incidence, or incidence in those treated in ICUs. Other important sources of bias are the duration of follow-up for patients admitted (for one day vs the entire hospital stay), case defi nition, type of institution, study site (restricted to ICU or not), seasonal variability, and casemix. 23 Results from US-based population studies from administrative data suggest a population-based incidence of 300 cases per 100 000 person-years for severe sepsis 24 and 240 cases per 100 000 person-years for sepsis. 25 When the setting is the ICU, most results show treated incidence of about ten cases per 100 ICU admissions. 26 Others have reported a much higher incidence in settings with fewer ICU beds, 27 probably indicating admission of very sick patients or exclusion of low-risk patients for postoperative monitoring from the denominator. 17 Similarly, in population-based studies of acute lung injury, results show an incidence of 18, 28 34, 29 and 79 cases 30 per 100 000 person-years in Scandinavia, Australia, and USA, respectively, with an estimated 74 500 deaths every year in the USA. 30 This number exceeds the yearly number of deaths from breast cancer, HIV/AIDS, and asthma, 31 and shows the underappreciated burden of critical illness to population health, at least in developed nations.

Application of these data to the world's population provides very rough estimates of the global burden of critical illness syndromes (table 1) . Of note, these values might underestimate the burden in developing countries, where a higher proportion of deaths is caused by infection and injury. In addition, they assume that the age, sex, risk factor distributions, and critical care capacity are similar to those of the North American populations that generated the epidemiological data. Even in the developed world, epidemiological data for availability of ICU beds are sparse (table 2) .

These challenges imply that the global burden of critical illness might never be possible to defi ne. Even the less ambitious goal of defi ning the global capacity to deliver critical care is diffi cult, in view of the absence of uniform defi nitions for an ICU bed, as noted in a study in which the results showed a fi ve or more fold variation in ICU bed availability in eight developed countries. 34 Nevertheless, meeting this goal is necessary to allocate health-system resources, improve the quality of care for critically ill patients, and plan for unexpected surges, such as during a pandemic. Defi nition of the global burden of critical illness would also provide impetus for initiatives to improve the outcomes of acutely ill adults in low-resource settings, such as the WHO's integrated management of adolescent and adult acute illness 

ICU mortality in unselected patients in North America, Europe, Australia, and New Zealand, studied for development of scoring systems, is 8-18%, and serial assessments of similar scoring systems suggest that overall ICU mortality over time might be falling. 21, 46, 47 However, these summary measures incorporate the generally excellent outcomes of patients admitted for routine monitoring and conceal the high mortality of the most acutely ill patients. For example, mortality is 35-45% 48 in heterogeneous cohorts of patients with acute lung injury and 50-60% 49 in patients with septic shock, for whom temporal improvements in mortality are slight at best. 24, 27, 48, 49 By contrast, mortality after myocardial infarction with ST-elevation is about 7% in developed world hospitals 50 and continues to decline. 51 Investigations have broadened consideration of ICU outcomes from short-term mortality to long-term mortality, morbidity, and quality of life (panel). 52 ICU survivors have to face challenges related to physical morbidity (muscle loss and weakness, contractures, pain) 53 and non-physical morbidity (depression, anxiety, post-traumatic stress disorder, long-lasting delirium, and cognitive im pairment). 54 Despite this growing recognition, clinicians do not have measures to prevent post-ICU morbidity while patients remain critically ill. The results of one prominent randomised trial suggested that the combination of daily interruption of sedation and early exercise and mobilisation improved functional outcomes at hospital discharge. 55 Whether this treatment is generalisable and feasible, and whether the eff ect is mainly driven by early exercise or by reduced sedation and delirium, remain to be seen. Similarly, strategies implemented after ICU discharge to decrease delayed morbidity remain elusive, 56 as shown by a recent randomised trial that identifi ed no benefi t of a manualbased, self-directed physical rehabilitation programme, including nurse-led clinic follow-up and screening for psychological morbidity. 56

Several reasons explain why the improvement of survival of critically ill patients has been harder to achieve than for those with single homogeneous diagnoses such as myocardial infarction. First, clinicians might not recognise critical illness until organ dysfunction is already advanced. 57 Attempts to augment clinicians' judgment of the severity of illness in hospital patients has led to the development of early warning scores, but these do not have enough sensitivity, reliability, and validity. 58 Second, there are few eff ective specifi c treatments for heterogeneous critical illness syndromes. For example, in many statistically negative randomised trials of treatments for acute lung injury, only avoidance of injurious tidal volume ventilation reduces mortality. 3 Even when an eff ective treatment exists, universal implementation has been diffi cult to achieve, 59 indicating the challenges of translating complex care protocols delivered by interdisciplinary teams to the patient's bedside. 60 This theme persists in examples of other eff ective supportive treatments, such as early aggressive resuscitation 61 and early appropriate anti biotics 62 in severe sepsis, enteral nutrition, 63 and weaning from mechanical ventilation. 64 Third, patients with critical-illness syndromes have variable severity of illness, burden of comorbidities, and baseline risk of mortality, all of which are broader than the narrow subset enrolled in randomised trials. 65 The evidence base for critical care therapeutics, derived from few positive randomised trials, thus might not be generalisable to many patients cared for in ICUs. 66 What global trends will aff ect the burden of critical illness?

Several emerging trends almost guarantee that the demand for critical care services will increase while the ability to pay for them will decrease.

With respect to patient demographics, the frequency of diseases and comorbid disorders that cause critical illness increases with age. As the rest of medicine advances, care has intensifi ed for high-risk patients with many comorbidities (such as diabetes mellitus, chronic kidney disease, congestive heart failure, chronic obstructive pulmonary disease, and cancer), compromised immune systems, and extreme old age. As these treatment boundaries are pushed, complications can be expected to increase. On the assumption of no eff ective prevention strategies for acute lung injury, extrapolation of present US epidemiology predicts over 330 000 cases per year by 2030, a 50% increase over present numbers. 30 Parallel increases can be expected for sepsis 24 demand might be especially acute in the USA, in which use of ICU by hospital patients who die is very high (47% vs 10% in England), especially for elderly people. 69 The combination of an ageing population and fewer young wage earners in developed countries will create a demand for critical care that cannot be fulfi lled as it is presently delivered, even if shrinking economies recover. The inverted demographic pyramid in developed nations will be mirrored by a predominantly youthful population in many developing nations, with high fertility rates and restricted public health and critical care infrastructure. In addition to the medical implications of an ageing population, the geopolitical consequences are expected to be profound and might include civic unrest and shifts in power from traditional economies. 70 With these inevitable demographic changes it seems that the burden of untreated critical illness in the developing world will increase, with poor outcomes, unless the present minimum ICU capacity grows.

Demand for intensivists' services will not only be driven by demographics, but also by their expanding role in inpatient care. In the USA, the number of ICU beds in hospitals increased by 26% from 1985 to 2000, whereas other inpatient beds decreased by 31%, with care shifted to other settings, indicating prioritisation of intensive care services. 71 Some have advocated for an increased role for intensivists outside the ICU by directing rapidresponse teams consisting of physicians, nurses, and respiratory therapists, whose mandate is to assess acutely ill patients on general wards and prevent critical illness by early intervention. 72 Like many treatments for critical illness, rapid-response teams have substantial pathophysiological rationale and supporting observational data. Although present evidence from clinical trials supporting this strategy is mixed, some health authorities and quality agencies are recommending it. 73 Data from a study of the outcomes of mechanical ventilation suggested that mortality associated with this intervention was lower at higher volume centres, 74 raising the hypothesis that population outcomes might be improved by regionalisation of intensive-care services. However, these observational data do not prove that patients would benefi t from regionalisation, and important barriers to the transfer of critically ill patients from lowvolume to high-volume centres exist. 75 Regionalisation of critical care services, like region alisation of trauma services, will increase requirements for critical care services at high-volume centres. Most critical care services are organised with a trained intensivist managing the ICU, a model known as intensivist staffi ng, although this model is not universal. Most studies exploring the eff ects of this model come from the USA, the country with the most variation in intensive care delivery models. Data generally suggest that intensivists improve patient outcomes, 76 possibly because they have the training and time commitment to provide complete care to very sick patients and their families, or because they are able to manage the critical care team most eff ectively. But this hypothesis does not lend itself to randomised trials, and the evidence is not uniform. 77 Hospital physicians and surgeons, who are playing an increasing role in the management of patients in US acute-care hospitals, might share responsibility for critically ill patients in settings in which intensivist staffi ng is not possible.

The overall eff ect of these and other decisions about hospital organisation on the demand for critical care services is unclear. Most seem to increase demand on a specialty that might have insuffi cient numbers and trainees. [78] [79] [80] Potential solutions to this shortfall are increased development and dissemination of guidelines and protocols, training of non-physician clinicians to substitute for intensivists, and telemedicine to allow experienced physicians and nurses to expand the geographical scope of their care. 81 The training and telemedicine approaches would need additional human and technological resources, which might be feasible in middle-income or high-income settings, but would challenge the capacity of health systems in the developing world. The evidence that either approach is a safe and eff ective substitute for intensivist staffi ng is slight.

Natural and human-generated events such as disasters and wars generate acute and unpredictably large numbers of critically ill patients. Examples in the modern medical era have been rare; however, this situation could change if a pandemic of infl uenza or another virulent infection emerges to cause respiratory or other organ dysfunction. The 2003 outbreak of severe acute respiratory syndrome (SARS), mostly localised to east Asia 82 and Toronto, Canada, 83 highlighted challenges that would be amplifi ed by a much broader pandemic: high illness severity of aff ected patients, stretched critical care resources diverted from general medicine and high-risk elective surgery to look after SARS patients, transmission to health-care workers, and high workload for remaining clinical staff . 84 Data from the present pandemic of H1N1 infl uenza show that in certain geographical areas the virus causes serious illness and death in young, previously healthy people, with a high burden of mechanically ventilated patients and deaths. 85, 86 Continuing wars, acts of terrorism, the 2004 tsunami in Asia, and the 2010 Haitian earthquake remind us that both human-generated and natural disasters can quickly overwhelm local health-care infrastructure in both developed and developing countries, even with mild to moderate numbers of casualties. Only recently has disaster management, including advance planning for surge capacity, mobile critical care, triage and rationing, hospital resource management, and staffi ng, become an integrated part of critical care academic activity. 87 However, during times of war, we should remember that evidence from systematic household cluster sampling suggests that most excess deaths, and, by extension, most demands for intensive care, do not arise from violence but from medical disorders resulting from the breakdown of public health infrastructure (eg, cholera), or from the discontinuation of treatment of chronic diseases caused by interruption of pharmaceutical supplies. 88, 89 In developing countries, these realities are aggravated by the presence of endemic diseases, such as HIV and trauma, that represent a substantial burden to health-care systems.

In terms of economics, the present fi nancial crisis will probably harm health-care delivery in both developed and developing countries by decreasing government and donor expenditures, diverting household funds for health care to other essential expenditures, and increasing competition for government services as private insurance becomes less aff ordable. 90 Critically ill patients will not be spared since their care consumes between 0·5% and 1% of gross domestic product, at least in North America. 71, 91 As the gross world product falls, the proportion consumed by health care in developed countries, and critical care specifi cally, will rise greatly, unless the demand for these services falls or their delivery becomes cheaper. Health-care funders facing these facts might focus spending on primary and preventive care. The present global recession and heightened disparities are drawing attention to decades-old questions. How eff ective is critical care? How cost eff ective is critical care? How can we ration a service perceived to rescue lives at imminent risk of death? 92 Despite these realities, US clinicians perceive little or no resource restraints on their ability to deliver intensive care. 93 Data for structure, casemix, care processes, and outcomes of critical care in least developed countries (as by the UN defi nition based on low income, human resource weakness, and economic vulnerability) are restricted to descriptive studies suggesting few beds in intensive care, infrastructure, personnel, and equipment. Patients are thus admitted to ICUs with very high illness severity, and, not surprisingly, narrative reviews suggest that clinical outcomes are poor. 94 Maximising use of this scarce resource (table 2) implies attention to regionalisation and integration, based on prevailing local realities. 39 Some have argued that fi nancial inequities and cultural expectations make the notion of considering intensive care in developing countries misguided, and a universally applicable critical care ethic impossible. 95 Mitigating arguments emphasise philosophical principles of universal justice and harm to national economies 96 of untreated critical illness. Extrapolating from diseasespecifi c data from the WHO's Global Health Observatory, infection and perinatal complications are much more common causes of admission to an ICU in the developing world than complications of chronic cardiac, vascular, and pulmonary disease, which predominate in the developed world. Before, little attention was focused on translation of intensive care techniques to low-resource settings, but more workers have now argued that safe emergency medical care is a worthwhile component of public health; 97 others have published practical proposals to extend evidence-based sepsis care to low-resource settings. 98 Any improvements to the delivery of critical care will need adequate numbers of trained health-care workers, 99 feasible care guidelines and protocols that can be scaled across low-resource settings, and reversal of the so-called brain drain to developed world health-care systems. 100

The young specialty of intensive care has evolved from its origins in treatment of poliomyelitis victims with respiratory failure, to an interdisciplinary team that cares for patients in an ICU, and to a broader mandate to treat critically ill patients irrespective of geographical location or use of specifi c technology. Determination of the global burden of critical-illness syndromes poses epidemiological challenges to separate the care for critically ill patients from the available intensive-care resources to treat them. Results from population-based studies in the developed world suggest that the burden of critical-illness syndromes is higher than generally appreciated and will increase as the population ages. Although intensive care capacity is scarce in the developing world, eff orts to improve the care of the critically ill in these settings are emerging. Unlimited expansion of intensive care to meet the needs of an ageing population and handle the consequences of natural disasters, confl ict, inadequate primary care, and high-risk treatments for very sick patients, will be challenged by high costs at a time of economic constraint. To meet this challenge, the specialty of intensive care will need to measure better the global burden of critical illness and develop both preventive and therapeutic interventions for the sickest patient. These interventions will need to be scalable across health-care systems at all the world's latitudes.

NKJA and GDR drafted the manuscript. NKJA, RAF, SB, and GDR revised the manuscript for important intellectual content.

We declare that we have no confl icts of interest.

The anaesthetist's viewpoint on the treatment of respiratory complications in poliomyelitis during the epidemic in Copenhagen

Evolution of the intensive care unit as a clinical center and critical care medicine as a discipline

The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome

Pulmonary artery catheters for adult patients in intensive care

Critical care medicine-a new specialty?

Critical illness outcomes in specialty versus general intensive care units

An international survey of training in adult intensive care medicine

The CoBaTrICE Collaboration. The educational environment for training in intensive care medicine: structures, processes, outcomes and challenges in the European region

Development of core competencies for an international training programme in intensive care medicine

Defi nitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis

The international sepsis forum consensus conference on defi nitions of infection in the intensive care unit

Defi nitions, mechanisms, relevant outcomes, and clinical trial coordination

An early PEEP/F I O 2 trial identifi es diff erent degrees of lung injury in patients with acute respiratory distress syndrome

Interobserver variability in applying a radiographic defi nition for ARDS

Health services research in critical care using administrative data

Withdrawal of mechanical ventilation in anticipation of death in the intensive care unit

Sepsis in European intensive care units: results of the SOAP study

The prevalence of nosocomial infection in intensive care units in Europe. Results of the European Prevalence of Infection in Intensive Care (EPIC) Study. EPIC International Advisory Committee

Characteristics and outcomes in adult patients receiving mechanical ventilation: a 28-day international study

End-of-life practices in European intensive care units: the Ethicus Study

SAPS 3-From evaluation of the patient to evaluation of the intensive care unit. Part 1: Objectives, methods and cohort description

The International Nosocomial Infection Control Consortium (INICC): goals and objectives, description of surveillance methods, and operational activities

Epidemiology of severe sepsis around the world

Epidemiology of severe sepsis in the United States: analysis of incidence, outcome, and associated costs of care

The epidemiology of sepsis in the United States from 1979 through 2000

Severe sepsis epidemiology: sampling, selection, and society

secondary analysis of a high quality clinical database, the ICNARC Case Mix Programme Database

Incidence and mortality after acute respiratory failure and acute respiratory distress syndrome in Sweden, Denmark, and Iceland. The ARF Study Group

The Australian and New Zealand Intensive Care Society Clinical Trials Group. Incidence and mortality of acute lung injury and the acute respiratory distress syndrome in three Australian States

Incidence and outcomes of acute lung injury

Epidemiology of acute lung injury

The changing epidemiology of mechanical ventilation: a population-based study

Mechanical ventilation in Ontario, 1992-2000: incidence, survival, and hospital bed utilization of noncardiac surgery adult patients

Variation in critical care services across North America and Western Europe

ICUs worldwide: results of a nationwide survey of Colombian intensive care units

An evaluation of the intensive care unit resources and utilization in Trinidad

Intensive care units in Croatia: 2001 survey

Large regional diff erences in Swedish intensive care. A nation-wide inquiry shows that the lowest number of beds is in big cities

National audit of critical care resources in South Africa-unit and bed distribution

Anesthesia and its allied disciplines in the developing world: a nationwide survey of the Republic of Zambia

Intensive Care Resources & Activity: Australia and New Zealand

China Critical Care Clinical Trial Group (CCCCTG)

An audit of state sector intensive care services in Sri Lanka

A surgical safety checklist to reduce morbidity and mortality in a global population

An estimation of the global volume of surgery: a modelling strategy based on available data

A new risk prediction model for critical care: the Intensive Care National Audit & Research Centre (ICNARC) model

Mortality and length-of-stay outcomes

Has mortality from acute respiratory distress syndrome decreased over time?: a systematic review

Current epidemiology of septic shock: the CUB-Rea Network

Predictors of hospital mortality in the global registry of acute coronary events

National trends in rates of death and hospital admissions related to acute myocardial infarction, heart failure and stroke

Quality of life in adult survivors of critical illness: a systematic review of the literature

One-year outcomes in survivors of the acute respiratory distress syndrome

Psychiatric morbidity in survivors of the acute respiratory distress syndrome: a systematic review

Early physical and occupational therapy in mechanically ventilated, critically ill patients: a randomised controlled trial

The PRaCTICaL study of nurse led, intensive care follow-up programmes for improving long term outcomes from critical illness: a pragmatic randomised controlled trial

Suboptimal care of patients before admission to intensive care. Is caused by a failure to appreciate or apply the ABCs of life support

Systematic review and evaluation of physiological track and trigger warning systems for identifying at-risk patients on the ward

Impact of randomized trial results on acute lung injury ventilator therapy in teaching hospitals

Barriers to providing lung-protective ventilation to patients with acute lung injury

Early goal-directed therapy in the treatment of severe sepsis and septic shock

Duration of hypotension before initiation of eff ective antimicrobial therapy is the critical determinant of survival in human septic shock

Canadian clinical practice guidelines for nutrition support in mechanically ventilated

Eff ect on the duration of mechanical ventilation of identifying patients capable of breathing spontaneously

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Eligibility criteria in randomized clinical trials in the critical care literature

Use of intensive care at the end of life in the United States: an epidemiologic study

Projected incidence of mechanical ventilation in Ontario to 2026: preparing for the aging baby boomers

Use of intensive care services during terminal hospitalizations in England and the United States

The graying of the great powers: demography and geopolitics in the 21st century

Critical care medicine in the United States 1985-2000: an analysis of bed numbers, use, and costs

Rapid response systems: a systematic review

Institute for Healthcare Improvement

Hospital volume and the outcomes of mechanical ventilation

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Physician staffi ng patterns and clinical outcomes in critically ill patients: a systematic review

Association between critical care physician management and patient mortality in the intensive care unit

Caring for the critically ill patient. Current and projected workforce requirements for care of the critically ill and patients with pulmonary disease: can we meet the requirements of an aging population

Critical care nursing: workforce issues and potential solutions

National audit of critical care resources in South Africa-nursing profi le

Remote ICU care programs: current status

A cluster of cases of severe acute respiratory syndrome in Hong Kong

Identifi cation of severe acute respiratory syndrome in Canada

Critically ill patients with severe acute respiratory syndrome

Critically ill patients with 2009 infl uenza A(H1N1) in Mexico

Critical Care Services and 2009 H1N1 Infl uenza in Australia and New Zealand

Task Force for Mass Critical Care. Summary of suggestions from the Task Force for Mass Critical Care summit

Mortality after the 2003 invasion of Iraq: a cross-sectional cluster sample survey

Mortality in the Democratic Republic of Congo: a nationwide survey

The global fi nancial crisis: an acute threat to health

The critical care crisis in the United States: a report from the profession

Bentham in a box: technology assessment and health care allocation

Perceptions of cost constraints, resource limitations, and rationing in United States intensive care units: results of a national survey

A review and analysis of intensive care medicine in the least developed countries

Critical care: why there is no global bioethics

Eff ects of maternal mortality on gross domestic product (GDP) in the WHO African region

Emergency medical care in developing countries: is it worthwhile?

Strategies to reduce mortality from bacterial sepsis in adults in developing countries

Human resources and health outcomes: cross-country econometric study

The metrics of the physician brain drain

We thank Martin Dünser for providing additional data from his study. 40