A 9-year, single-institution, retrospective review of death rate and prognostic factors in adult respiratory distress syndrome

Association between age and acute respiratory distress syndrome development and mortality following trauma

BACKGROUND

Improved understanding of the relationship between patient age and acute respiratory distress syndrome (ARDS) development and mortality following traumatic injury may help facilitate generation of new hypotheses about ARDS pathophysiology and the role of novel treatments to improve outcomes across the age spectrum.

METHODS

We conducted a retrospective cohort study of trauma patients included in the National Trauma Data Bank who were admitted to an intensive care unit from 2007 to 2016. We determined ARDS incidence and mortality across eight age groups for the entire 10-year study period and by year. We used generalized linear Poisson regression models adjusted for underlying mortality risk (injury mechanism, Injury Severity Score, admission Glasgow Coma Scale score, admission heart rate, and admission hypotension).

RESULTS

Acute respiratory distress syndrome occurred in 3.1% of 1,297,190 trauma encounters. Acute respiratory distress syndrome incidence was lowest among pediatric patients and highest among adults aged 35 to 64 years. Acute respiratory distress syndrome mortality was highest among patients 80 years or older (43.9%), followed by 65 to 79 years (30.6%) and 4 years or younger (25.3%). The relative risk of mortality associated with ARDS was highest among the pediatric age groups, with an adjusted relative risk (aRR) of 2.06 (95% confidence interval [CI], 1.72-2.70) among patients 4 years or younger compared with an aRR of 1.51 (95% CI, 1.42-1.62) for the entire cohort. Acute respiratory distress syndrome mortality increased over the 10-year study period (aRR, 1.03 per year; 95% CI, 1.02-1.05 per year), whereas all-cause mortality decreased (aRR, 0.98 per year; 95% CI, 0.98-0.99 per year).

CONCLUSIONS

While ARDS development following traumatic injury was most common in middle-aged adults, patients 4 years or younger and 65 years or older with ARDS experienced the highest burden of mortality. Children 4 years or younger were disproportionately affected by ARDS relative to their low underlying mortality following trauma that was not complicated by ARDS. Acute respiratory distress syndrome-associated mortality following trauma has worsened over the past decade, emphasizing the need for new prevention and treatment strategies.

LEVEL OF EVIDENCE

Prognostic/epidemiological study, level III.

Modelling Thirty-day Mortality in the Acute Respiratory Distress Syndrome (ARDS) in an Adult ICU

Variables predicting thirty-day outcome from Acute Respiratory Distress Syndrome (ARDS) were analysed using Cox regression structured for time-varying covariates. Over a three-year period, 1996–1998, consecutive patients with ARDS (bilateral chest X-ray opacities, PaO2/FiO2 ratio of <200 and an acute precipitating event) were identified using a prospective computerized data base in a university teaching hospital ICU.

The cohort, 106 mechanically ventilated patients, was of mean (SD) age 63.5 (15.5) years and 37% were female. Primary lung injury occurred in 45% and 24% were postoperative. ICU-admission day APACHE II score was 25 (8); ARDS onset time from ICU admission was 1 day (median: range 0-16) and 30 day mortality was 41% (95% CI: 33%-51%). At ARDS onset, PaO2/FiO2 ratio was 92 (31), 81% had four-quadrant chest X-ray opacification and lung injury score was 2.75 (0.45). Average mechanical ventilator tidal volume was 10.3 ml/ predicted kg weight. Cox model mortality predictors (hazard ratio, 95% CI) were: APACHE II score, 1.15 (1.09-1.21); ARDS lag time (days), 0.72 (0.58-0.89); direct versus indirect injury, 2.89 (1.45-5.76); PaO2/FiO2 ratio, 0.98 (0.97-0.99); operative versus non-operative category, 0.24 (0.09-0.63). Time-varying effects were evident for PaO2/FiO2 ratio, operative versus non-operative category and ventilator tidal volume assessed as a categorical predictor with a cut-point of 8 ml/kg predicted weight (mean tidal volumes, 7.1 (1.9) vs 10.7 (1.6) ml/kg predicted weight). Thirty-day survival was improved for patients ventilated with lower tidal volumes.

Survival predictors in ARDS were multifactorial and related to patient-injury-time interaction and level of mechanical ventilator tidal volume.

Epidemiological profile of acute respiratory distress syndrome patients: A tertiary care experience

Background:

Acute respiratory distress syndrome (ARDS) is seen in critically ill patients. Its etiological spectrum in India is expected to be different from that seen in western countries due to the high prevalence of tropical infections.

Aim:

To study the epidemiological profile of ARDS patients.

Setting:

A tertiary care hospital in Karnataka, India.

Materials and Methods:

Retrospective analysis of 150 out of the 169 ARDS patients diagnosed during 2010–2012. Data collected included the clinical features and severity scoring parameters.

Results:

The mean age of the study population was 42.92 ± 13.91 years. The causes of ARDS included pneumonia (n = 35, 23.3%), scrub typhus (n = 33, 22%), leptospirosis (n = 11, 7.3%), malaria (n = 6, 4%), influenza (H1N1) (n = 10, 6.7%), pulmonary tuberculosis (n = 2, 1.3%), dengue (n = 1, 0.7%), abdominal sepsis (n = 16, 10.7%), skin infection (n = 3, 2%), unknown cause of sepsis (n = 18, 12%), and nonseptic causes (n = 15, 10%). A total of 77 (51.3%) patients survived, 66 (44%) expired, and 7 (4.7%) were discharged against medical advice (AMA). Preexisting comorbidities (46) were present in 13 survivors, 19 nonsurvivors, and four discharged AMA. History of surgery prior to the onset of ARDS was present in one survivor, 13 nonsurvivors, and one discharge AMA. Mean Acute Physiology and Chronic Health Evaluation (APACHE) II, APACHE III, and Sequential Organ Failure Assessment scores in survivors were 9.06 ± 4.3, 49.22 ± 14, and 6.43 ± 2.5 and in nonsurvivors 21.11 ± 7, 86.45 ± 23.5, and 10.6 ± 10, respectively.

Conclusion:

The most common cause of ARDS in our study was pneumonia, but a large percentage of cases were due to the tropical infections. Preexisting comorbidity, surgery prior to the onset of ARDS, higher severity scores, and organ failure scores were more frequently observed among nonsurvivors than survivors.

Acute Respiratory Distress Syndrome: Mortality in a Single Center According to Different Definitions

BACKGROUND

Mortality in acute lung injury (ALI) remains high, with outcome data arising mostly from multicenter studies. We undertook this investigation to determine hospital mortality in patients with ALI in a single center.

METHODS

We studied patients admitted between 2005 and 2012 with ALI and acute respiratory distress syndrome (ARDS) according to the American European Consensus Conference (AECC) criteria and recorded clinical variables. Thereafter, patients were classified as subgroups according to the AECC and Berlin definition in order to compare the clinical characteristics and outcomes.

RESULTS

In the 93 patients comprising the study, hospital mortality was 38%. Mortality at 28 days was 36%. Multivariate analysis associated hospital mortality with age and Pao₂/Fio₂ on day 1 ( P < .001). Differences resulted between the subgroups of AECC (ALI vs ARDS) and Berlin (mild vs moderate vs severe ARDS) in the lung injury score, Pao₂/Fio₂, Pao₂/P_Ao₂, PaCo₂ on day 1, and hospital mortality.

CONCLUSION

The overall hospital mortality (38%) was similar to that of other studies and according to the presence of ARDS (Pao₂/Fio₂ ≤ 200), we found significant differences between ALI and ARDS (AECC) and between mild and moderate or severe ARDS (Berlin) in baseline respiratory variables and mortality.

Benchmarking outcomes in the critically injured burn patient

OBJECTIVE

To determine and compare outcomes with accepted benchmarks in burn care at 6 academic burn centers.

BACKGROUND

Since the 1960s, US morbidity and mortality rates have declined tremendously for burn patients, likely related to improvements in surgical and critical care treatment. We describe the baseline patient characteristics and well-defined outcomes for major burn injuries.

METHODS

We followed 300 adults and 241 children from 2003 to 2009 through hospitalization, using standard operating procedures developed at study onset. We created an extensive database on patient and injury characteristics, anatomic and physiological derangement, clinical treatment, and outcomes. These data were compared with existing benchmarks in burn care.

RESULTS

Study patients were critically injured, as demonstrated by mean % total body surface area (TBSA) (41.2 ± 18.3 for adults and 57.8 ± 18.2 for children) and presence of inhalation injury in 38% of the adults and 54.8% of the children. Mortality in adults was 14.1% for those younger than 55 years and 38.5% for those aged 55 years and older. Mortality in patients younger than 17 years was 7.9%. Overall, the multiple organ failure rate was 27%. When controlling for age and % TBSA, presence of inhalation injury continues to be significant.

CONCLUSIONS

This study provides the current benchmark for major burn patients. Mortality rates, notwithstanding significant % TBSA and presence of inhalation injury, have significantly declined compared with previous benchmarks. Modern day surgical and medically intensive management has markedly improved to the point where we can expect patients younger than 55 years with severe burn injuries and inhalation injury to survive these devastating conditions.

Ventilatory strategies in septic patients. Results from a nationwide observational trial

BACKGROUND

Mortality in intensive care unit (ICU) patients is affected by multiple variables. The possible impact of the mode of ventilation has not yet been clarified; therefore, a secondary analysis of the "epidemiology of sepsis in Germany" study was performed. The aims were (1) to describe the ventilation strategies currently applied in clinical practice, (2) to analyze the association of the different modes of ventilation with mortality and (3) to investigate whether the ratio between arterial partial pressure of oxygen and inspired fraction of oxygen (PF ratio) and/or other respiratory variables are associated with mortality in septic patients needing ventilatory support.

METHODS

A total of 454 ICUs in 310 randomly selected hospitals participated in this national prospective observational 1-day point prevalence of sepsis study including 415 patients with severe sepsis or septic shock according to the American College of Chest Physicians/Society of Critical Care Medicine criteria.

RESULTS

Of the 415 patients, 331 required ventilatory support. Pressure controlled ventilation (PCV) was the most frequently used ventilatory mode (70.6 %) followed by assisted ventilation (AV 21.7 %) and volume controlled ventilation (VCV 7.7 %). Hospital mortality did not differ significantly among patients ventilated with PCV (57 %), VCV (71 %) or AV (51 %, p=0.23). A PF ratio equal or less than 300 mmHg was found in 83.2 % of invasively ventilated patients (n=316). In AV patients there was a clear trend to a higher PF ratio (204±70 mmHg) than in controlled ventilated patients (PCV 179±74 mmHg, VCV 175±75 mmHg, p=0.0551). Multiple regression analysis identified the tidal volume to pressure ratio (tidal volume divided by peak inspiratory airway pressure, odds ratio OR=0.94, 95 % confidence interval 95% CI=0.89-0.99), acute renal failure (OR=2.15, 95% CI=1.01-4.55) and acute physiology and chronic health evaluation (APACHE) II score (OR=1.09, 95% CI=1.03-1.15) but not the PF ratio (univariate analysis OR=0.998, 95 % CI=0.995-1.001) as independent risk factors for in-hospital mortality.

CONCLUSIONS

This representative survey revealed that severe sepsis or septic shock was frequently associated with acute lung injury. Different ventilatory modes did not affect mortality. The tidal volume to inspiratory pressure ratio but not the PF ratio was independently associated with mortality.

Capillary leak syndrome in trauma: what is it and what are the consequences?

TICS is a complex disease that is clearly multifactorial in the traumatically injured patient (Fig. 2). Although systemic inflammation that occurs directly as a result of injury plays the most prominent role, the local tissue and organ injury effects of trauma not only cause local capillary leak and edema but also further amplify the SIRS response. High volume fluid administration and hypoproteinemic states further exacerbate the problem. All of this leads to organ dysfunction and failure, which is the third leading cause of death following injury. Strategies to treat TICS and attenuate its effects once it occurs by targeting inflammatory pathways have been wholly unsuccessful. The mainstay of therapy for TICS is prevention and minimization of its lethal effects. Newer resuscitation strategies such as hemostatic resuscitation and early goal-directed therapies are currently the best available strategies to combat TICS. Whether these result in better outcomes remains to be seen and the authors anxiously await the results of well-designed prospective trials.

A simple classification model for hospital mortality in patients with acute lung injury managed with lung protective ventilation

OBJECTIVE

Despite improvements in the care of critically ill patients, hospital mortality rate for acute lung injury remains high at approximately 40%. We developed a classification rule to stratify mechanically ventilated patients with acute lung injury according to hospital mortality and compared this rule with the Acute Physiology and Chronic Health Evaluation III prediction.

PATIENTS

We used data of 2,022 participants in Acute Respiratory Distress Syndrome Network trials to build a classification rule based on 54 variables collected before randomization.

DESIGN

We used a classification tree approach to stratify patients according to hospital mortality using a training subset of 1800 participants and estimated expected prediction errors using tenfold crossvalidation. We validated our classification tree using a subset of 222 participants not included in model building and calculated areas under the receiver operating characteristic curves.

MEASUREMENTS AND MAIN RESULTS

We identified combinations of age (>63 yrs), blood urea nitrogen (>15 mg/dL), shock, respiratory rate (>21 breaths/min), and minute ventilation (>13.9 L/min) as important predictors of hospital mortality at 90 days. The classification tree had a similar expected prediction error in the training set (28% vs. 26%; p = .18) and areas under the receiver operating characteristic curve in the validation set (0.71 vs. 0.73; p = .71) as did a model based on Acute Physiology and Chronic Health Evaluation III.

CONCLUSIONS

Our tree-based classification rule performed similarly to Acute Physiology and Chronic Health Evaluation III in stratifying patients according to hospital mortality, is simpler to use, contains risk factors that may be specific to acute lung injury, and identified minute ventilation as a potential novel predictor of death in patients with acute lung injury.

Epidemiology of ARDS and ALI

Acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) are distinctly modern clinical entities. Recent epidemiologic research has taken advantage of large cohorts in efforts to better describe these highly lethal syndromes with a focus on differentiation of clinically meaningful subtypes and early prediction in an effort to improve treatment and prevention. This article identifies the most significant studies and systematic reviews of recent years, defining the incidence, mortality, risk and prognostic factors, and etiologic classes of ARDS/ALI.

Outcome prediction in pneumonia induced ALI/ARDS by clinical features and peptide patterns of BALF determined by mass spectrometry

Background

Peptide patterns of bronchoalveolar lavage fluid (BALF) were assumed to reflect the complex pathology of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) better than clinical and inflammatory parameters and may be superior for outcome prediction.

Methodology/Principal Findings

A training group of patients suffering from ALI/ARDS was compiled from equal numbers of survivors and nonsurvivors. Clinical history, ventilation parameters, Murray's lung injury severity score (Murray's LISS) and interleukins in BALF were gathered. In addition, samples of bronchoalveolar lavage fluid were analyzed by means of hydrophobic chromatography and MALDI-ToF mass spectrometry (MALDI-ToF MS).

Receiver operating characteristic (ROC) analysis for each clinical and cytokine parameter revealed interleukin-6>interleukin-8>diabetes mellitus>Murray's LISS as the best outcome predictors. Outcome predicted on the basis of BALF levels of interleukin-6 resulted in 79.4% accuracy, 82.7% sensitivity and 76.1% specificity (area under the ROC curve, AUC, 0.853). Both clinical parameters and cytokines as well as peptide patterns determined by MALDI-ToF MS were analyzed by classification and regression tree (CART) analysis and support vector machine (SVM) algorithms. CART analysis including Murray's LISS, interleukin-6 and interleukin-8 in combination was correct in 78.0%. MALDI-ToF MS of BALF peptides did not reveal a single identifiable biomarker for ARDS. However, classification of patients was successfully achieved based on the entire peptide pattern analyzed using SVM. This method resulted in 90% accuracy, 93.3% sensitivity and 86.7% specificity following a 10-fold cross validation (AUC = 0.953). Subsequent validation of the optimized SVM algorithm with a test group of patients with unknown prognosis yielded 87.5% accuracy, 83.3% sensitivity and 90.0% specificity.

Conclusions/Significance

MALDI-ToF MS peptide patterns of BALF, evaluated by appropriate mathematical methods can be of value in predicting outcome in pneumonia induced ALI/ARDS.

Bone marrow derived mesenchymal stem cells inhibit inflammation and preserve vascular endothelial integrity in the lungs after hemorrhagic shock

Hemorrhagic shock (HS) and trauma is currently the leading cause of death in young adults worldwide. Morbidity and mortality after HS and trauma is often the result of multi-organ failure such as acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), conditions with few therapeutic options. Bone marrow derived mesenchymal stem cells (MSCs) are a multipotent stem cell population that has shown therapeutic promise in numerous pre-clinical and clinical models of disease. In this paper, in vitro studies with pulmonary endothelial cells (PECs) reveal that conditioned media (CM) from MSCs and MSC-PEC co-cultures inhibits PEC permeability by preserving adherens junctions (VE-cadherin and β-catenin). Leukocyte adhesion and adhesion molecule expression (VCAM-1 and ICAM-1) are inhibited in PECs treated with CM from MSC-PEC co-cultures. Further support for the modulatory effects of MSCs on pulmonary endothelial function and inflammation is demonstrated in our in vivo studies on HS in the rat. In a rat “fixed volume” model of mild HS, we show that MSCs administered IV potently inhibit systemic levels of inflammatory cytokines and chemokines in the serum of treated animals. In vivo MSCs also inhibit pulmonary endothelial permeability and lung edema with concurrent preservation of the vascular endothelial barrier proteins: VE-cadherin, Claudin-1, and Occludin-1. Leukocyte infiltrates (CD68 and MPO positive cells) are also decreased in lungs with MSC treatment. Taken together, these data suggest that MSCs, acting directly and through soluble factors, are potent stabilizers of the vascular endothelium and inflammation. These data are the first to demonstrate the therapeutic potential of MSCs in HS and have implications for the potential use of MSCs as a cellular therapy in HS-induced lung injury.

A prospective cohort study of ALI/ARDS in the Tohoku district of Japan (second report)

PURPOSE

We previously reported a study of systemic inflammatory response syndrome (SIRS) cases in the Tohoku district of Japan in which the patients showed a 30-day mortality from acute lung injury/acute respiratory distress syndrome (ALI/ARDS) of about 20%. Cases in which chest X-ray findings did not meet ALI/ARDS criteria were diagnosed as acute hypoxemic respiratory failure (AHRF), but about 50% of these patients progressed to ALI/ARDS. The objective of this study was to verify the findings obtained in the earlier study and to gain further insights into the pathognomonic symptoms of AHRF associated with SIRS.

METHODS

A prospective cohort study was performed in SIRS patients admitted to the intensive care unit (ICU) with PaO(2)/fractional inspired oxygen (FIO(2)) < or = 300 mmHg. Patients were assigned to ALI or ARDS groups based on symptoms at ICU entry. Cases in which chest X-ray showed no infiltration shadows in bilateral lung fields were classified as AHRF.

RESULTS

A total of 240 patients were enrolled in the study. The 30-day mortalities were 21.6% and 20.0% in the ALI and ARDS groups, respectively. Of the 88 AHRF patients, 49 progressed to ALI/ARDS, with progression occurring within 3 days after ICU entry in most cases; 39 patients recovered with no progression. Chest X-ray and computed tomography (CT) showed no findings indicating ALI/ARDS in 20 AHRF patients at ICU entry, but 7 of these patients progressed to ALI/ARDS.

CONCLUSION

The mortality rates of ALI and ARDS were 21.6% and 20.5%, respectively. More than half of the AHRF patients progressed to ALI or ARDS. Some AHRF patients had normal findings on chest CT, but subsequently showed a bilateral shadow on a chest X-ray. This indicates that mild pathologic lesions may not show imaging abnormalities.

Timing of acute respiratory distress syndrome onset is related to patient outcome

BACKGROUND/PURPOSE

Acute respiratory distress syndrome (ARDS) is a major cause of mortality and morbidity in adult intensive care units. The relationship between the timing of ARDS onset and outcome is not well known. The objective of this study was to investigate the outcome of patients with late-onset ARDS during hospitalization.

METHODS

We prospectively enrolled patients who were intubated and fulfilled ARDS criteria in medical and surgical intensive care units in a tertiary referral medical center from December 1, 2004 to May 31, 2006. Those who developed ARDS more than 48 hours after hospital admission were categorized as late-onset ARDS; otherwise, they were defined as early-onset ARDS. We assessed the risk factors for hospital mortality using multivariate analysis and 90-day survival using Kaplan-Meier analysis between early- and late-onset ARDS, and between direct and indirect ARDS.

RESULTS

A total of 172 patients were included in the study. Overall mortality rate was 70%. Late-onset ARDS [odds ratio (OR): 3.06; 95% confidence interval (CI): 1.41 to 6.63; p = 0.005] and initial shock (OR: 8.20; 95% CI: 3.39-19.79; p < 0.001) were the independent risk factors for hospital mortality. Patients with late-onset ARDS had higher hospital mortality rate (83% vs. 60%; p = 0.002), longer duration of mechanical ventilation (27.0 +/- 23.4 vs. 14.6 +/- 11.5 days; p < 0.001) and length of intensive care unit stay (25.5 +/- 20.6 vs. 15.6 +/- 13.6 days; p < 0.001) than patients with early-onset ARDS. The 90-day survival showed that both early-onset ARDS and direct ARDS were associated with better survival.

CONCLUSION

Patients with late-onset ARDS are associated with poor prognosis and should be managed as high-risk patients.

Late death after multiple severe trauma: when does it occur and what are the causes?

INTRODUCTION

The information about the long-term mortality and causes of death after multiple injuries is sparse. In general, most follow-up studies report on 1 year to 3 years maximum follow up. The current literature focuses on causes of death immediately after trauma or during the initial in-hospital stay. We report on long-term mortality and causes of death in patients with multiple injures up to 30 years after the initial injury.

METHODS AND MATERIAL

We analyzed the causes of death using patient files, inquiries of patients' relatives, and death certificates. Inclusion criteria are (1) polytrauma (PT) (Injury Severity Score > or = 16) between 1973 and 1990; (2) age 3 years to 60 years at injury; (3) admission to the hospital alive; and (4) death during the study period. Patients were separated into two groups: patients deceased during the initial hospital stay (in-hospital deaths, n = 408) and patients deceased after discharge (postdischarge deaths, n = 103). The survival of the PT victims was compared descriptively with age- and gender-matched data from the general population (GP).

RESULTS

Causes of death in in-hospital deaths are head injury (37%), adult respiratory distress syndrome (14%), sepsis (11%), hemorrhagic shock (10%), pneumonia (9%), multiple organ failure (9%), and others (10%). Causes of death after discharge included cardiovascular diseases (23%), second major trauma (19%), neurologic diseases (16%), suicide (10%), malignancies (6%), and others (26%). The analysis of survival showed a higher mortality for PT compared with the GP group during the first year after the event (p < 0.05). Between 2 years and 10 years after the event, the annual mortality of the PT-group approximates the GP group.

CONCLUSION

PT patients who die after discharge from the initial hospitalization show other causes of death than age-matched controls of the general population. Among these are second major trauma and suicide. Future studies should investigate whether certain social or psychologic factors might play a role.

30 years of polytrauma care: An analysis of the change in strategies and results of 4849 cases treated at a single institution

The quality and progress of treatment of 4849 multiple trauma patients treated at one institution was reviewed retrospectively. Three periods, 1975-1984 (decade I; n=1469) and 1985-1994 (decade II; n=1937) and 1995-2004 (decade III; n=1443) were compared. 65% of multiple trauma patients had cerebral injuries, 58% thoracic trauma and 81% extremity fractures (37% open injuries). Injury combinations decreased during all decades with head/extremity injuries being the most common combination. Throughout the three decades pre-hospital care became more aggressive with an increase of intravenous fluid resuscitation (I: 80%, II: 97%, III: 98%). Chest tube insertion decreased after an initial increase (I: 41%, II: 83%, III: 27%) as well as intubation (I: 82%, II: 94%, III: 59%). Rescue times were progressively shortened. For initial clinical diagnosis of massive abdominal haemorrhage ultrasound (I: 17%, II: 92%, III: 97%) replaced peritoneal lavage (I: 44%, II: 28%, III: 0%). CT-scans were used more frequently for the initial diagnosis of head injuries and other injuries to the trunk throughout the observation time. With regard to complications, acute renal failure decreased by half (I: 8.4%; II: 3.7%; III: 3.9%), ARDS initially decreased but increased again in the last decade (I: 18.1%, II: 13.4%, III: 15.3%), whereas the rate of multiple organ dysfunction syndrome (MODS) increased continuously (I: 14.2%, II: 18.9%, III: 19.8%) probably due to a decline of the mortality rate from 37% in the first to 22% in the second and 18% in the third decade and parallel increase of the time of death. These treatment results summarise the enormous clinical effort as well as medical progress in polytrauma management over the past 30 years. Further reduction of mortality is desirable, but probably only possible when immediate causal therapy of later posttraumatic organ failure can be established.

Predictors of hospital mortality in a population-based cohort of patients with acute lung injury

OBJECTIVE

Studies describing predictors of mortality in patients with acute lung injury were primarily derived from selected academic centers. We sought to determine the predictors of mortality in a population-based cohort of patients with acute lung injury and to characterize the performance of current severity of illness scores in this population.

DESIGN

Secondary analysis of a prospective, multicenter, population-based cohort.

SETTING

Twenty-one hospitals in Washington State.

PATIENTS

The cohort included 1,113 patients with acute lung injury identified during the year 1999-2000.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We evaluated physiology, comorbidities, risk factors for acute lung injury, and other variables for their association with death at hospital discharge. Bivariate predictors of death were entered into a multiple logistic regression model. We compared Acute Physiology and Chronic Health Evaluation (APACHE) II, APACHE III, and Simplified Acute Physiology Score II to the multivariable model using area under the receiver operating characteristic curve. The model was validated in an independent cohort of 886 patients with acute lung injury. Modified acute physiology score, age, comorbidities, arterial pH, minute ventilation, PaCO2, PaO2/FiO2 ratio, intensive care unit admission source, and intensive care unit days before onset of acute lung injury were independently predictive of in-hospital death (p < .05). The area under the receiver operating characteristic curve for the multivariable model was superior to that of APACHE III (.81 vs. .77, p < .001) but was no different after external validation (.71 vs. .70, p = .64).

CONCLUSIONS

The predictors of mortality in patients with acute lung injury are similar to those predictive of mortality in the general intensive care unit population, indicating disease heterogeneity within this cohort. Accordingly, APACHE III predicts mortality in acute lung injury as well as a model using variables selected specifically for patients with acute lung injury.

The analysis of risk factors of impacting mortality rate in severe multiple trauma patients with posttraumatic acute respiratory distress syndrome

OBJECTIVE

We hypothesize that not all of the traditional risk factors of impacting mortality rate in commonly traumatic populations with posttraumatic acute respiratory distress syndrome (ARDS) are independently associated with those patient populations identified with severe multiple trauma. Rather, we postulate that there may exist significantly different impacting degrees of specific risk factors in stratified patients (surviving beyond 24 and 96 hours)--more severe multiple trauma with higher injury score and long-term mechanical ventilation as well.

METHODS

This is a retrospective cohort study regarding trauma as a single cause for emergency intensive care unit admission. Twenty-two items of potential risk factors of impacting mortality rate were calculated by univariate and multivariate logistic analyses to find distinctive items in these severe multiple trauma patients.

RESULTS

The unadjusted odds ratio and 95% confidence intervals of mortality rate were found to be associated with 6 (out of 22) risk factors, namely, (1) Acute Physiology and Chronic Health Evaluation II score, (2) duration of trauma factor, (3) aspiration of gastric contents, (4) sepsis, (5) pulmonary contusion, and (6) duration of mechanical ventilation. Significant results also appeared in stratified patients.

CONCLUSIONS

Impact of pulmonary contusion and Acute Physiology and Chronic Health Evaluation II score contributing to prediction of mortality may exist in the early phase after trauma. Sepsis is still a vital risk factor referring to systemic inflammatory response syndrome, infection, secondary multiple organ dysfunction, etc. Discharging trauma factors as early as possible becomes the critical therapeutic measure. Aspiration of gastric contents in emergency intensive care unit admission could lead to incremental mortality rate due to aspiration pneumonia. Long-standing mechanical ventilation should be constrained because it is likely to cause severe refractory complications.

Mortality rates for patients with acute lung injury/ARDS have decreased over time

BACKGROUND

Over the last decade, several studies have suggested that survival rates for patients with acute lung injury (ALI) or ARDS may have improved. We performed a systematic analysis of the ALI/ARDS literature to document possible trends in mortality between 1994 and 2006.

METHODS

We used the Medline database to select studies with the key words "acute lung injury," "ARDS," "acute respiratory failure," and "mechanical ventilation." All studies that reported mortality rates for patients with ALI/ARDS defined according to the criteria of the American European Consensus Conference were selected. We excluded studies with < 30 patients and studies limited to specific subgroups of ARDS patients such as sepsis, trauma, burns, or transfusion-related ARDS.

RESULTS

Seventy-two studies were included in the analysis. There was a wide variation in mortality rates among the studies (15 to 72%). The overall pooled mortality rate for all studies was 43% (95% confidence interval, 40 to 46%). Metaregression analysis suggested a significant decrease in overall mortality rates of approximately 1.1%/yr over the period analyzed (1994 to 2006). The mortality reduction was also observed for hospital but not for ICU or 28-day mortality rates.

CONCLUSIONS

In this literature review, the data are consistent with a reduction in mortality rates in general populations of patients with ALI/ARDS over the last 10 years.

Leukoreduction is Associated with a Decreased Incidence of Late Onset Acute Respiratory Distress Syndrome after Injury

Transfusions are known to be associated with Acute Respiratory Distress Syndrome (ARDS). Transfusion of leukoreduced products may be associated with a decreased incidence of late posttraumatic ARDS (late ARDS). Data from ventilated and transfused trauma patients were analyzed. Key variables in the first 48 hours of admission were studied for their associations with late ARDS and examined for changes over the 6 year study period. Late ARDS developed in 244 of the 1488 patients studied (16.4%). The incidence in patients given nonleukoreduced (NLR) product was 30.4 per cent (75/247) versus 13.6 per cent (169/1241) for patients not exposed [2.77 (2.02–3.73), P < 0.001]. Exposure to NLR products (50.9% in 2000 vs 1.9% in 2005) and incidence of ARDS (26.3% in 2000 vs 6.3% in 2005) significantly decreased. Treatment variables independently associated with late ARDS were NLR product exposure, Total Parenteral Nutrition exposure, Peak Inspiratory Pressure ≥ 30 mm Hg, fluid balance ≥ 2 liters at 48 hours, and transfusion of ≥ 10 units of any product. NLR product exposure has an association with an increased incidence of late onset posttraumatic ARDS which is independent of large volume transfusions. Leukoreduction should be routinely included in an overall treatment strategy to furthermore mitigate this complication in critically ill trauma patients.

Modelling survival in acute severe illness: Cox versus accelerated failure time models

BACKGROUND

The Cox model has been the mainstay of survival analysis in the critically ill and time-dependent covariates have infrequently been incorporated into survival analysis.

OBJECTIVES

To model 28-day survival of patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), and compare the utility of Cox and accelerated failure time (AFT) models.

METHODS

Prospective cohort study of 168 adult patients enrolled at diagnosis of ALI in 21 adult ICUs in three Australian States with measurement of survival time, censored at 28 days. Model performance was assessed as goodness-of-fit [GOF, cross-products of quantiles of risk and time intervals (P > or = 0.1), Cox model] and explained variation ('R2', Cox and ATF).

RESULTS

Over a 2-month study period (October-November 1999), 168 patients with ALI were identified, with a mean (SD) age of 61.5 (18) years and 30% female. Peak mortality hazard occurred at days 7-8 after onset of ALI/ARDS. In the Cox model, increasing age and female gender, plus interaction, were associated with an increased mortality hazard. Time-varying effects were established for patient severity-of-illness score (decreasing hazard over time) and multiple-organ-dysfunction score (increasing hazard over time). The Cox model was well specified (GOF, P > 0.34) and R2 = 0.546, 95% CI: 0.390, 0.781. Both log-normal (R2 = 0.451, 95% CI: 0.321, 0.695) and log-logistic (R2 0.470, 95% CI: 0.346, 0.714) AFT models identified the same predictors as the Cox model, but did not demonstrate convincingly superior overall fit.

CONCLUSIONS

Time dependence of predictors of survival in ALI/ARDS exists and must be appropriately modelled. The Cox model with time-varying covariates remains a flexible model in survival analysis of patients with acute severe illness.

Prevention and treatment of post-traumatic acute respiratory distress syndrome

Post-Traumatic Acute Respiratory Distress Syndrome (ARDS) is a major cause of morbidity and mortality in the acutely injured patient. The American-European Consensus Conference Report established the most widely accepted definition of ARDS in 1994. In recent years it appears the incidence and impact of the disease are on the decline. This article reviews strategies to prevent and treat post-traumatic ARDS. Well-accepted, proven strategies include lung protective ventilation strategies, as well as conservative transfusion and crystalloid resuscitation policies and the adoption of leukoreduction techniques. Other modalities including hypertonic saline resuscitation, use of albumin and diuretics, positive end expiratory pressure, high-frequency ventilation, prone positioning, recruitment maneuvers, extracorporeal membrane oxygenation, corticosteroids, exogenous surfactant, and inhaled nitric oxide are also reviewed.

The decreasing incidence of late posttraumatic acute respiratory distress syndrome: the potential role of lung protective ventilation and conservative transfusion practice

BACKGROUND

A reduction in the incidence of posttraumatic Acute Respiratory Distress Syndrome (ARDS) has been demonstrated. It is hypothesized that ventilation strategies and restrictive transfusion policies are contributory. The purpose of this study is to examine the changes in ventilation and transfusion parameters over time and their associations with late posttraumatic ARDS.

METHODS

The surgical intensive care unit and blood bank databases from a Level I center during a 6-year period were analyzed. All mechanically ventilated trauma patients were screened for ARDS with onset after 48 hours of admission (late ARDS). Demographic, injury, resuscitation, ventilation parameters, and transfusion data were extracted. Variables were analyzed for significant changes during the duration of the study, and independent associations with ARDS were determined.

RESULTS

There were 2,346 eligible patients and 192 (8.2%) of them met criteria for late ARDS. There was a significant decrease in the incidence of late ARDS by year (14.9% in 2000 to 3.8% in 2005). When comparing the first and second half of the study, there was a significant decrease in the percentage of patients transfused with packed red blood cells (49.0% versus 40.7%), patients with a peak inspiratory pressure > or = 30 mm Hg (64.9% versus 50.1%), and patients ventilated with a tidal volume/kg > or = 10 mL/kg (39.6% versus 21.8%). Early transfusions, peak inspiratory pressure > or = 30 mm Hg, and fluid balance > or = 2 L in the first 48 hours of admission were independently associated with ARDS.

CONCLUSIONS

The increasing use of restrictive transfusion policies and ventilation strategies that potentially limit elevations in early peak inspiratory pressures are associated with a decreased incidence of late posttraumatic ARDS.

Reciprocal congenic lines of mice capture the aliq1 effect on acute lung injury survival time

Acute lung injury (ALI) is a devastating condition resulting from diverse causes. Genetic studies of human populations indicate that ALI is a complex disease with substantial phenotypic variance, incomplete penetrance, and gene-environment interactions. To identify genes controlling ALI mortality, we previously investigated mean survival time (MST) differences between sensitive A/J (A) and resistant C57BL/6J (B) mice in ozone using quantitative trait locus (QTL) analysis. MST was significantly linked to QTLs (Aliq1-3) on chromosomes 11, 13, and 17, respectively. Additional QTL analyses of separate and combined backcross and F(2) populations supported linkage to Aliq1 and Aliq2, and established significance for previously suggestive QTLs on chromosomes 7 and 12 (named Aliq5 and Aliq6, respectively). Decreased MSTs of corresponding chromosome substitution strains (CSSs) verified the contribution of most QTL-containing chromosomes to ALI survival. Multilocus models demonstrated that three QTLs could explain the MST difference between progenitor strains, agreeing with calculated estimates for number of genes involved. Based on results of QTL genotype analysis, a double CSS (B.A-6,11) was generated that contained Aliq1 and Aliq4 chromosomes. Surprisingly, MST and pulmonary edema after exposure of B.A-6,11 mice were comparable to B mice, revealing an unpredicted loss of sensitivity compared with separate CSSs. Reciprocal congenic lines for Aliq1 captured the corresponding phenotype in both background strains and further refined the QTL interval. Together, these findings support most of the previously identified QTLs linked to ALI survival and established lines of mice to further resolve Aliq1.

Nuclear factor-kappaB activation in neonatal mouse lung protects against lipopolysaccharide-induced inflammation

RATIONALE

Injurious agents often cause less severe injury in neonates as compared with adults.

OBJECTIVE

We hypothesized that maturational differences in lung inflammation induced by lipopolysaccharide (LPS) may be related to the nature of the nuclear factor (NF)-kappaB complex activated, and the profile of target genes expressed.

METHODS

Neonatal and adult mice were injected with intraperitoneal LPS. Lung inflammation was assessed by histology, and apoptosis was determined by TUNEL (terminal deoxynucleotidyl transferase UTP nick-end labeling). The expression of candidate inflammatory and apoptotic mediators was evaluated by quantitative real-time polymerase chain reaction and Western immunoblot.

RESULTS

Neonates demonstrated reduced inflammation and apoptosis, 24 hours after LPS exposure, as compared with adults. This difference was associated with persistent activation of NF-kappaB p65p50 heterodimers in the neonates in contrast to early, transient activation of p65p50 followed by sustained activation of p50p50 in the adults. Adults had increased expression of a panel of inflammatory and proapoptotic genes, and repression of antiapoptotic targets, whereas no significant changes in these mediators were observed in the neonates. Inhibition of NF-kappaB activity in the neonates decreased apoptosis, but heightened inflammation, with increased expression of the same inflammatory genes elevated in the adults. In contrast, inhibition of NF-kappaB in the adults resulted in partial suppression of the inflammatory response.

CONCLUSIONS

NF-kappaB activation in the neonatal lung is antiinflammatory, protecting against LPS-mediated lung inflammation by repressing similar inflammatory genes induced in the adult.

Acute lung injury and the acute respiratory distress syndrome: challenges in clinical trial design

Despite significant advances in the understanding of the complex pathophysiology, only a limited number of new treatments for acute lung injury (ALI) have emerged in the last 2 decades. This article discusses some of the challenges that remain in conducting clinical research in patients who have ALI and acute respiratory distress syndrome. New definitions that incorporate prognostic measures and reduce patient heterogeneity will allow more efficient enrollment of patients. Delineating outcomes attributable to the lung injury will improve the power of studies to detect significant treatment effects. Future collaborative studies will be needed to investigate longer-term clinical outcomes.

Why do patients who have acute lung injury/acute respiratory distress syndrome die from multiple organ dysfunction syndrome? Implications for management

Acute respiratory distress syndrome (ARDS) affects some 10% to 15% of ICU patients and is associated with mortality rates of 40% to 50%. Although ARDS is the most severe form of acute respiratory failure, refractory hypoxia is an uncommon cause of death in these patients. The majority of patients who have ARDS die from multiple-organ dysfunction syndrome (MODS), and ARDS should, therefore, be seen as a systemic disease. Improved understanding of the systemic factors involved in the development and evolution of ARDS and MODS should facilitate the development of new therapeutic agents that will improve outcomes in these patients.

Postoperative acute respiratory distress syndrome development in the thoracic surgery patient

Acute respiratory distress syndrome (ARDS) in the thoracic surgery patient is a dreaded complication that occurs in 4% to 5% of pneumonectomies. This peculiar syndrome is indistinct from other forms of ARDS yet is associated with an exceedingly higher mortality rate. Current management parallels ARDS treatment of other etiologies.

The decreasing incidence and mortality of acute respiratory distress syndrome after injury: a 5-year observational study

BACKGROUND

Acute respiratory distress syndrome (ARDS) after major trauma has been associated with increased morbidity and mortality rates. Recently, there have been marked advances in defining etiologic factors and optimal management strategies for ARDS. We sought to examine whether there has been a corresponding change in the incidence and outcomes of ARDS after injury in recent years.

METHODS

A prospective observational study of all adult trauma intensive care unit (ICU) admissions over 5 years. Patients were evaluated daily for predefined ARDS criteria. Patient data, illness and injury severity, and ARDS incidence were compared by year of admission. Logistic regression analysis was used to identify independent predictors of ARDS and mortality.

RESULTS

There were 1,913 patients identified; the majority were male (79%) and suffered blunt trauma (62%). Two hundred seventy-four patients (14%) met criteria for ARDS. The incidence of ARDS showed a significant decrease from 23% in 2000 to rates of 8.4% and 9% for 2003 and 2004 (p < 0.01), respectively. There was no significant difference by year for trauma mechanism, age, sex, Injury Severity Score, Acute Physiology and Chronic Health Evaluation, ICU length of stay, or mortality. The strongest independent predictor of ARDS was year of ICU admission, with an odds ratio of 2.9 (95% confidence interval, 1.7-5.0) for admission in 2000 versus subsequent years (p < 0.001). After adjusting for age and injury severity, patients with ARDS had more days on mechanical ventilation and longer hospital and ICU stays (all p < 0.01), but there was no significant difference in mortality with or without ARDS (p = 0.57).

CONCLUSION

There has been a more than 50% reduction in the incidence of ARDS after injury during the past 5 years in our institution despite similar patient demographics and injury severities. Development of ARDS increased hospital and ICU stays but not hospital mortality.

High tidal volume and positive fluid balance are associated with worse outcome in acute lung injury

STUDY OBJECTIVES

Recent data have suggested that ventilatory strategy could influence outcomes from acute lung injury (ALI) and ARDS. We tested the hypothesis that infection/sepsis and use of higher tidal volumes than those applied in the ARDS Network (ARDSnet) study (> 7.4 mL/kg of predicted body weight) would worsen outcome in patients with ALI/ARDS.

DESIGN

International cohort, observational study.

SETTING

One hundred ninety-eight European ICUs participating in the Sepsis Occurrence in Acutely Ill Patients study.

PATIENTS OR PARTICIPANTS

All 3,147 adult patients admitted to one of the participating ICUs between May 1, 2002, and May 15, 2002.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Patients were followed up until death, hospital discharge, or for 60 days. Of the 3,147 patients, 393 patients (12.5%) had ALI/ARDS. ICU and hospital mortality was higher in patients with ALI/ARDS than those without ALI/ARDS (38.9% vs 15.6% and 45.5% vs 21.0%, respectively; p < 0.001). A multivariable logistic regression analysis with ICU outcome as the dependent factor showed that the independent risks for mortality were as follows: presence of cancer, use of tidal volumes higher than those used by the ARDSnet study, degree of multiorgan dysfunction, and higher mean fluid balance. Sepsis, septic shock, and oxygenation at the onset of ALI/ARDS were not independently associated with higher mortality rates.

CONCLUSIONS

In addition to comorbidities and organ dysfunction, high tidal volumes and positive fluid balance are associated with a worse outcome from ALI/ARDS.

Prognostic determinants of acute respiratory distress syndrome in adults: impact on clinical trial design

OBJECTIVE

The objective of this study was to review known clinical predictors and biologic markers of adverse clinical outcomes in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) that might be used as selection criteria in clinical trials of novel therapies for ALI/ARDS.

DATA SOURCE

Published studies on clinical predictors and biologic markers of adverse outcomes in ALI/ARDS.

MAIN RESULTS

In large epidemiologic studies, a number of clinical factors have been identified consistently as independent predictors of mortality in ALI/ARDS. These include age, comorbidities, including chronic liver disease and immunosuppression, severity of illness scores, and the degree of multisystem organ failure. Several biologic markers of mortality have also been identified in large studies, including von Willebrand factor antigen, surfactant protein D, protein C, plasminogen activator inhibitor-1, interleukins 6 and 8, and the TNF receptors. The Pao2/Fio2 ratio at the onset of ALI/ARDS does not predict clinical outcome but may be more useful after the first day of ALI/ARDS. A persistently low Pao2/Fio2 ratio is associated with worse outcomes and may be a marker of failure to respond to conventional therapy. Changes in IL-6, IL-8, TNF receptors, and SP-D over the first 3 days of ALI/ARDS are also associated with adverse clinical outcomes. The use of a combination of clinical factors and biologic markers is a promising strategy that needs to be prospectively validated.

CONCLUSIONS

The design of clinical trials for new therapies for ALI and ARDS is a complex problem that ultimately will have a major impact on both trial outcome and generalizability. A number of clinical factors and biologic markers can be used to differentiate groups of patients at highest risk for adverse clinical outcomes. Whether enriching study populations with these sicker patients will increase or decrease the likelihood of a treatment effect for a given therapy is unknown.

Effect of acute lung injury and acute respiratory distress syndrome on outcome in critically ill trauma patients

OBJECTIVE

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are known to be associated with increased mortality and costs in trauma patients. We estimated the independent impact of these conditions on mortality and cost, beyond the severity of injury with which they are correlated.

DESIGN

One-year prospective cohort.

PATIENTS AND SETTING

All trauma patients admitted to the intensive care unit in a level I center were evaluated daily for ALI/ARDS using the American-European Consensus Conference definition.

MEASUREMENTS AND MAIN RESULTS

The main outcome measures were hospital mortality and costs. Logistic regression was used to model hospital mortality in relation to the presence of ALI and ARDS, adjusting for trauma severity (Injury Severity Score), Acute Physiology Score, and age. Hospital costs were modeled using multivariable linear regression. Of the 1,296 trauma patients surviving beyond the first day, 4% experienced ALI (defined as Pao2/Fio2 of 201-300 mm Hg) and 12% had ARDS (Pao2/Fio2 < or = 200 mm Hg). The crude relative risk of mortality was 2.24 (95% confidence interval, 0.92-5.45) in patients with ALI and 3.84 (95% confidence interval, 2.41-6.13) in patients with ARDS compared with those without ALI/ARDS. However, there was no association of mortality with ALI (relative risk, 0.99; 95% confidence interval, 0.29-3.36) or with ARDS (relative risk, 1.23; 95% confidence interval, 0.63-2.43) after adjustment for age, Injury Severity Score, and Acute Physiology Score. Among patients of comparable age, severity score, and length of stay, median cost was 20% to 30% higher for those with ALI/ARDS.

CONCLUSIONS

There is no additional mortality associated with ALI/ARDS above and beyond the factors that can be measured at intensive care unit admission. Therefore, mortality in trauma patients is explained by injury severity at admission and is not affected by the subsequent occurrence of ALI/ARDS. Nonetheless, ALI/ARDS was associated with increased intensive care unit stay and hospital cost, independent of trauma severity.

Multiple Organ Failure in Trauma Patients

SUMMARY

BACKGROUND As care of the critically ill patient has improved and definitions of organ failure have changed, it has been observed that the incidence of organ failure and the mortality associated with organ failure appear to be decreasing. In addition, many early studies included large heterogeneous populations of both medical and surgical patients that may have influenced the incidence and outcome of organ failure. The purpose of this study is to establish the current incidence and mortality of organ failure in a homogenous population of critically ill trauma patients. METHODS All trauma patients admitted to the intensive care unit (ICU) at an urban Level I trauma center were prospectively studied. Patients were evaluated for the presence of organ failure using definitions proposed by Knaus and by Fry. Newer definitions of organ failure incorporating organ dysfunction and severity-of-illness scores were also obtained in all patients in an attempt to predict outcome. These included lung injury scores (acute respiratory distress syndrome scores), Acute Physiology and Chronic Health Evaluation (APACHE) II and III scores, Injury Severity Score (ISS), and multiple organ dysfunction scores. Primary outcomes assessed were death and the occurrence of organ failure by the various definitions. RESULTS Eight hundred sixty-nine trauma patients were admitted to the ICU and survived longer than 48 hours. Mean APACHE II and APACHE III scores at admission to the ICU and ISS were 12.2 +/- 22, 30.5 +/- 22.7, and 19 +/- 10, respectively. Single organ failure (SOF) occurred in 163 patients (18.7%) and multiple organ failure occurred in 44 patients (5.1%). All SOF was caused by respiratory failure. Respiratory failure occurred first in the majority of patients with multiple organ failure. Mortality was 4.3% with one organ system failure, 32% with two, 67% with three, and 90% when four organ systems failed. None of the patients with SOF died secondary to respiratory failure. Multiple stepwise regression analysis was performed to determine which of the following risk factors are associated with the occurrence of organ failure: mechanism of injury, lactate at 24 hours, ISS, APACHE II, APACHE III, acute respiratory distress syndrome score at admission, multiple organ dysfunction score at admission and total blood products transfused in 24 hours. Of these factors, APACHE III, lactate at 24 hours, and total blood products transfused in 24 hours were associated with the occurrence of organ failure. CONCLUSION The overall incidence of organ failure in a homogeneous trauma population appears to be lower than that reported in studies performed in heterogeneous patient populations in the 1980s. Mortality for SOF is low and appears to be related primarily to the patient's underlying injuries and not to organ failure. Mortality for two or three organ system failures is lower than reported 15 to 20 years ago. Mortality for patients with four or more organ system failures remains high, approaching 100%.

Quality of life in acute respiratory distress syndrome survivors may be no worst than in other ICU survivors

OBJECTIVE

To compare the health-related quality of life (HR-QOL) in acute respiratory distress syndrome (ARDS) survivors with that in a matched control group of non-ARDS survivors.

DESIGN AND SETTING

Prospective, matched, parallel cohort study, comparing HR-QOL between intensive care unit (ICU) survivors with ARDS and a control group in a tertiary care hospital.

PATIENTS

Between May 1997 and December 2000, all ARDS adult patients of an eight-bed medical/surgical unit of a tertiary care hospital were enrolled and a control group of non-ARDS survivors, matched for severity of disease and for previous health state, was selected. The study included 29 ARDS survivors who answered the EQ-5D questionnaire and had lung function evaluated.

MEASUREMENTS AND RESULTS

A follow-up appointment was performed 6 months after ICU discharge consisting of: (a) evaluation of HR-QOL using EQ-5D and (b) lung function tests and measure of diffusing capacity. Among ARDS survivors 41% had normal lung function and 59% mild to moderate lung function impairments. Nearly a one-third of ARDS survivors reported problems in one or more of the five dimensions of the EQ-5D, and 48% reported feeling worse at the interview than 6 month before ICU admission. No significant differences were found in HR-QOL between ARDS survivors and other ICU survivors with similar age and matched for previous health state and severity of disease.

CONCLUSIONS

This study suggests that impairments in HR-QOL among ARDS survivors may not be distinguishable from that among other ICU survivors.

Epidemiology of acute lung injury

OBJECTIVE

To review the epidemiology of acute lung injury (ALI) with particular emphasis on its effect on public health.

DATA SOURCES

Published studies on the definitions, incidence, and outcomes of ALI.

DATA SUMMARY

ALI is a syndrome of acute hypoxemic respiratory failure that is not primarily cardiac in origin. The diagnostic criteria for the syndrome have not been well studied for their reliability or validity. The lack of a gold standard for the diagnosis of ALI is a challenge to clinical investigation. Recent data on the incidence of ALI (20-50 cases/105 person-years) indicate that it is more common than previous estimates for the incidence of acute respiratory distress syndrome (3-8 cases/105 person-years). There is conflicting evidence as to whether the mortality rate in the broader patient population with ALI is different from the mortality rate in acute respiratory distress syndrome. Mortality attributable to and associated with ALI in the United States is comparable to HIV infection, breast cancer, and asthma. Morbidity from impaired cognitive function, functional status, and psychiatric complications has been reported in survivors of ALI.

CONCLUSIONS

Recent studies of the epidemiology of ALI have reported higher incidence rates for this syndrome than previously described. The mortality and morbidity rates associated with ALI are considerable, with significant impact on public health.

Epidemiology and outcome of acute respiratory failure in intensive care unit patients

OBJECTIVES

To summarize the prevalence of various forms of acute respiratory failure in acutely ill patients and review the major factors involved in the outcome of these patients.

DATA SOURCES AND SELECTION

MEDLINE search for published studies reporting the prevalence or outcome for patients with acute respiratory failure and cited reference studies and abstracts from a recent international meeting in the intensive care medicine field.

DATA SYNTHESIS AND EXTRACTION

From the selected articles, information was obtained regarding the prevalence of acute respiratory failure, including acute respiratory distress syndrome and acute lung injury as defined by the North American-European Consensus Conference, the outcome, and the factors influencing mortality rates in this population of patients.

CONCLUSIONS

The prevalence of acute respiratory failure varies according to the definition used and the population studied. Nonsurvivors of acute respiratory distress syndrome die predominantly of respiratory failure in <20% of cases. The relatively high mortality rates of acute lung injury/acute respiratory distress syndrome are primarily related to the underlying disease, the severity of the acute illness, and the degree of organ dysfunction.

Aspiration-related illnesses: definitions and diagnosis

BACKGROUND

Aspiration is a leading cause of morbidity and mortality. It is the most common cause of pneumonia and one of the most serious adverse effects of enteral nutrition support. It is important to use standardized terminology to define and discuss aspiration-related illnesses.

METHODS

Review of the medical literature and extraction of definitions and descriptions of aspiration-related illnesses.

RESULTS

Definitions, clinical features, diagnosis, and treatment of common aspiration-related illnesses are discussed.

CONCLUSIONS

Precisely defined terminology of aspiration-related illnesses adds consistency to this area of medicine and simplifies analysis and comparison of clinical studies.