The Changing Face of Organ Failure in ARDS *

Ligustilide, a novel SIRT1 agonist, alleviates lipopolysaccharide-induced acute lung injury through deacetylation of NICD

Development and progression of sepsis-induced acute lung injury (ALI) involve apoptosis and oxidative stress in lung epithelial cells. Ligustilide (LIG) is one of the main bioactive constituents derived from the Angelica sinensis. As a novel SIRT1 agonist, LIG owns powerful anti-inflammatory and antioxidative properties, exerting remarkable therapeutic effects on cancers, neurological disorders, and diabetes mellitus. However, whether LIG could protect against lipopolysaccharide (LPS)-induced ALI by activating SIRT1 remains unclear. Mice underwent intratracheal LPS injection to mimic sepsis-induced ALI while MLE-12 cells were treated with LPS for 6 h to establish an in vitro ALI model. At the same time, mice or MLE-12 cells were treated with different doses of LIG to access its pharmacological effect. The results demonstrated that LIG pretreatment could improve LPS-induced pulmonary dysfunction and pathological injury, apart from increasing 7-day survival rate. In addition, LIG pretreatment also decreased inflammation, oxidative stress and apoptosis during LPS-induced ALI. Mechanically, LPS stimulation decreased the expression and activity of SIRT1 but increased the expression of Notch1 and NICD. And LIG could also enhance the interaction between SIRT1 and NICD, thus deacetylating NICD. In vitro experiments also unveiled that EX-527, a selective SIRT1 inhibitor, could abolish LIG-elicited protection in LPS-treated MLE-12 cells. And in SIRT1 knockout mice with ALI, LIG pretreatment also lost its effects on inflammation, apoptosis, and oxidative stress during ALI.

Association between PaO2/FiO2 ratio and thrombotic events in COVID-19 patients

PaO₂/FiO₂ (P/F ratio) is considered a marker of hypoxia/hypoxemia and mortality. Several prothrombotic changes are associated with the decrease of P/F ratio. The role of P/F ratio in patients with arterial and venous thrombosis remains unclear. The aim of this study was to assess in patients with coronavirus disease 2019 (COVID-19), the association between P/F ratio and arterial/venous thrombosis. One thousand and four hundred and six COVID-19 patients were recruited; 289 (21%) patients had P/F ratio < 200 and 1117 (79%) ≥ 200. Compared to the patients with P/F ratio ≥ 200, those with P/F ratio < 200 were older and with higher levels of glycemia, D-dimer and lower levels of albumin. Multiple linear regression analysis showed that albumin (standardized coefficient β:  0.156; SE: 0.001; p = 0.0001) and D-dimer (standardized coefficient β: -0.135; SE: 0.0001; p = 0.0001) were associated with P/F ratio. During the hospitalization 159 patients were transferred in intensive care unit (ICU), 253 patients died, 156 patients had arterial or venous thrombotic events. A bivariate logistic analysis was performed to analyze the predictors of thrombosis in COVID-19 patients; P/F ratio < 200 (Odds Ratio: [OR] 1.718, 95% Confidence Interval [CI] 1.085-2.718, p = 0.021), albumin (OR 1.693, 95% CI 1.055-2.716, p = 0.029), D-dimer (OR 3.469, 95% CI 2.110-5.703, p < 0.0001), coronary artery disease (CAD) (OR 1.800, 95% CI 1.086-2.984, p = 0.023) and heart failure (OR 2.410 95% CI 1.385-4.193, p = 0.002) independently predicted thrombotic events in this population. This study suggests that the P/F ratio is associated with thrombotic events by promoting a hypercoagulation state in patients hospitalized for COVID-19.

Comparison of Clinical Characteristics and Predictors of Mortality between Direct and Indirect ARDS

Background and Objectives: Acute Respiratory Distress Syndrome (ARDS) is a heterogeneous syndrome that encompasses lung injury from a direct pulmonary or indirect systemic insult. Studies have shown that direct and indirect ARDS differ in their pathophysiologic process. In this study, we aimed to compare the different clinical characteristics and predictors of 28-day mortality between direct and indirect ARDS. Materials and Methods: The data of 1291 ARDS patients from September 2012 to December 2021 at the Second Affiliated Hospital of Chongqing Medical University were reviewed. We enrolled 451 ARDS patients in our study through inclusion and exclusion criteria. According to the risk factors, each patient was divided into direct (n = 239) or indirect (n = 212) ARDS groups. The primary outcome was 28-day mortality. Results: The patients with direct ARDS were more likely to be older (p < 0.001) and male (p = 0.009) and have more comorbidity (p < 0.05) and higher 28-day mortality (p < 0.001) than those with indirect ARDS. Age and multiple organ dysfunction syndrome (MODS) were predictors of 28-day mortality in the direct ARDS group, while age, MODS, creatinine, prothrombin time (PT), and oxygenation index (OI) were independent predictors of 28-day mortality in the indirect ARDS group. Creatinine, PT, and OI have interactions with ARDS types (all p < 0.01). Conclusions: The patients with direct ARDS were more likely to be older and male and have worse conditions and prognoses than those with indirect ARDS. Creatinine, PT, and OI were predictors of 28-day mortality only in the indirect ARDS group. The differences between direct and indirect ARDS suggest the need for different management strategies of ARDS.

P50 implies adverse clinical outcomes in pediatric acute respiratory distress syndrome by reflecting extrapulmonary organ dysfunction

Hypoxemia and multiple organ dysfunction are significant contributors to mortality in patients with pediatric acute respiratory distress syndrome (PARDS). P50, the oxygen tension at which hemoglobin is 50% saturated, is a measure of hemoglobin-oxygen affinity, and its alteration might have implications for tissue hypoxia and organ dysfunction. The purpose of this single-center, retrospective study was to evaluate P50 levels in PARDS and to determine the association between P50 and clinical outcomes. The study included 212 children diagnosed with PARDS according to the Pediatric Acute Lung Injury Consensus Conference definition who required invasive mechanical ventilation and had arterial blood gas results of hemoglobin oxygen saturation < 97% at the time of diagnosis. P50 levels were calculated using Doyle’s method, and organ dysfunction was assessed using the Pediatric Logistic Organ Dysfunction-2 score. Most patients exhibited more than one dysfunctional extrapulmonary organ at PARDS onset. P50 increased with increasing PARDS severity (mild (26.6 [24.9–29.6]), moderate (26.8 [25.0–29.5]), and severe PARDS (29.1 [26.1–32.4] mmHg; P = 0.025). Moreover, P50 demonstrated a significant positive association with extrapulmonary organ dysfunction score (β = 0.158, P = 0.007) and risk of mortality (adjusted hazard ratio, 1.056; 95% confidence interval, 1.015–1.098; P = 0.007), irrespective of initial PARDS severity. The relationship between P50 and mortality was largely mediated by extrapulmonary organ dysfunction. A high P50 value at the time of PARDS diagnosis may be associated with mortality via dysfunctional extrapulmonary organs. Future studies should consider P50 as a potential candidate index for risk stratification of PARDS patients.

Histopathological findings and clinicopathologic correlation in COVID-19: a systematic review

The severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2) pandemic has had devastating effects on global health and worldwide economy. Despite an initial reluctance to perform autopsies due to concerns for aerosolization of viral particles, a large number of autopsy studies published since May 2020 have shed light on the pathophysiology of Coronavirus disease 2019 (COVID-19). This review summarizes the histopathologic findings and clinicopathologic correlations from autopsies and biopsies performed in patients with COVID-19. PubMed and Medline (EBSCO and Ovid) were queried from June 4, 2020 to September 30, 2020 and histopathologic data from autopsy and biopsy studies were collected based on 2009 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 58 studies reporting 662 patients were included. Demographic data, comorbidities at presentation, histopathologic findings, and virus detection strategies by organ system were collected. Diffuse alveolar damage, thromboembolism, and nonspecific shock injury in multiple organs were the main findings in this review. The pathologic findings emerging from autopsy and biopsy studies reviewed herein suggest that in addition to a direct viral effect in some organs, a unifying pathogenic mechanism for COVID-19 is ARDS with its known and characteristic inflammatory response, cytokine release, fever, inflammation, and generalized endothelial disturbance. This study supports the notion that autopsy studies are of utmost importance to our understanding of disease features and treatment effect to increase our knowledge of COVID-19 pathophysiology and contribute to more effective treatment strategies.

Early individualized positive end-expiratory pressure guided by electrical impedance tomography in acute respiratory distress syndrome: a randomized controlled clinical trial

Background

Individualized positive end-expiratory pressure (PEEP) by electrical impedance tomography (EIT) has potential interest in the optimization of ventilation distribution in acute respiratory distress syndrome (ARDS). The aim of the study was to determine whether early individualized titration of PEEP with EIT improved outcomes in patients with ARDS.

Methods

A total of 117 ARDS patients receiving mechanical ventilation were randomly assigned to EIT group (n = 61, PEEP adjusted based on ventilation distribution) or control group (n = 56, low PEEP/FiO₂ table). The primary outcome was 28-day mortality. Secondary and exploratory outcomes were ventilator-free days, length of ICU stay, incidence of pneumothorax and barotrauma, and difference in Sequential Organ Failure Assessment (SOFA) score at day 1 (ΔD1-SOFA) and day 2 (ΔD2-SOFA) compared with baseline.

Measurements and main results

There was no statistical difference in the value of PEEP between the EIT group and control group, but the combination of PEEP and FiO₂ was different between groups. In the control group, a significantly positive correlation was found between the PEEP value and the corresponding FiO₂ (r = 0.47, p < 0.00001) since a given matched table was used for PEEP settings. Diverse combinations of PEEP and FiO₂ were found in the EIT group (r = 0.05, p = 0.68). There was no significant difference in mortality rate (21% vs. 27%, EIT vs. control, p = 0.63), ICU length of stay (13.0 (7.0, 25.0) vs 10.0 (7.0, 14.8), median (25th–75th percentile); p = 0.17), and ventilator-free days at day 28 (14.0 (2.0, 23.0) vs 19.0 (0.0, 24.0), p = 0.55) between the two groups. The incidence of new barotrauma was zero. Compared with control group, significantly lower ΔD1-SOFA and ΔD2-SOFA were found in the EIT group (p < 0.001) in a post hoc comparison. Moreover, the EIT group exhibited a significant decrease of SOFA at day 2 compared with baseline (paired t-test, difference by − 1 (− 3.5, 0), p = 0.001). However, the control group did show a similar decrease (difference by 1 (− 2, 2), p = 0.131).

Conclusion

Our study showed a 6% absolute decrease in mortality in the EIT group: a statistically non-significant, but clinically non-negligible result. This result along with the showed improvement in organ function might justify further reserach to validate the beneficial effect of individualized EIT-guided PEEP setting on clinical outcomes of patients with ARDS.

Trial registration: ClinicalTrials, NCT02361398. Registered 11 February 2015—prospectively registered, https://clinicaltrials.gov/show/NCT02361398.

Acute Respiratory Distress Syndrome in Cancer Patients

Acute respiratory distress syndrome (ARDS) is a heterogeneous form of acute, diffuse lung injury that is characterized by dysregulated inflammation, increased alveolar-capillary interface permeability, and non-cardiogenic pulmonary edema. In the general population, the incidence and mortality associated with ARDS over the last two decades have steadily declined in parallel with optimized approaches to pneumonia and other underlying causes of ARDS as well as increased utilization of multimodal treatment strategies that include lung-protective ventilation. In the cancer settings, significant declines in the incidence and mortality of ARDS over the past two decades have also been reported, although these rates remain significantly higher than those in the general population. Epidemiologic studies identify infection, including disseminated fungal pneumonias, as a major underlying cause of ARDS in the cancer setting. More than half of cancer patients who develop ARDS will not survive to hospital discharge. Those who do survive often face a protracted and often incomplete recovery, resulting in significant long-term physical, psychological, and cognitive sequelae. The residual organ dysfunction and poor functional status after ARDS may delay or preclude subsequent cancer treatments. As such, close collaboration between the critical care physicians and oncology team is essential in identifying and reversing the underlying causes and optimizing treatments for cancer patients with ARDS. This chapter reviews the diagnosis and common causes of ARDS in cancer and gives an update on the general management principles for cancer patients with ARDS in the ICU.

B7H3 ameliorates LPS-induced acute lung injury via attenuation of neutrophil migration and infiltration

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by an excessive inflammatory response within the lungs and severely impaired gas exchange resulting from alveolar-capillary barrier disruption and pulmonary edema. The costimulatory protein B7H3 functions as both a costimulator and coinhibitor to regulate the adaptive and innate immune response, thus participating in the development of microbial sepsis and pneumococcal meningitis. However, it is unclear whether B7H3 exerts a beneficial or detrimental role during ALI. In the present study we examined the impact of B7H3 on pulmonary inflammatory response, polymorphonuclear neutrophil (PMN) influx, and lung tissue damage in a murine model of lipopolysaccharide (LPS)-induced direct ALI. Treatment with B7H3 protected mice against LPS-induced ALI, with significantly attenuated pulmonary PMN infiltration, decreased lung myeloperoxidase (MPO) activity, reduced bronchoalveolar lavage fluid (BALF) protein content, and ameliorated lung pathological changes. In addition, B7H3 significantly diminished LPS-stimulated PMN chemoattractant CXCL2 production by inhibiting NF-κB p65 phosphorylation, and substantially attenuated LPS-induced PMN chemotaxis and transendothelial migration by down-regulating CXCR2 and Mac-1 expression. These results demonstrate that B7H3 substantially ameliorates LPS-induced ALI and this protection afforded by B7H3 is predominantly associated with its inhibitory effect on pulmonary PMN migration and infiltration.

The acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is a major cause of acute respiratory failure. Its development leads to high rates of mortality, as well as short- and long-term complications, such as physical and cognitive impairment. Therefore, early recognition of this syndrome and application of demonstrated therapeutic interventions are essential to change the natural course of this devastating entity. In this review article, we describe updated concepts in ARDS. Specifically, we discuss the new definition of ARDS, its risk factors and pathophysiology, and current evidence regarding ventilation management, adjunctive therapies, and intervention required in refractory hypoxemia.

Mechanical ventilation worsens abdominal edema and inflammation in porcine endotoxemia

INTRODUCTION

We hypothesized that mechanical ventilation per se increases abdominal edema and inflammation in sepsis and tested this in experimental endotoxemia.

METHODS

Thirty anesthetized piglets were allocated to one of five groups: healthy control pigs breathing spontaneously with continuous positive pressure of 5 cm H2O or mechanically ventilated with positive end-expiratory pressure of 5 cm H2O, and endotoxemic piglets during mechanical ventilation for 2.5 hours and then continued on mechanical ventilation with positive end-expiratory pressure of either 5 or 15 cm H2O or switched to spontaneous breathing with continuous positive pressure of 5 cm H2O for another 2.5 hours. Abdominal edema formation was estimated by isotope technique, and inflammatory markers were measured in liver, intestine, lung, and plasma.

RESULTS

Healthy controls: 5 hours of spontaneous breathing did not increase abdominal fluid, whereas mechanical ventilation did (Normalized Index increased from 1.0 to 1.6; 1 to 3.3 (median and range, P<0.05)). Endotoxemic animals: Normalized Index increased almost sixfold after 5 hours of mechanical ventilation (5.9; 4.9 to 6.9; P<0.05) with twofold increase from 2.5 to 5 hours whether positive end-expiratory pressure was 5 or 15, but only by 40% with spontaneous breathing (P<0.05 versus positive end-expiratory pressure of 5 or 15 cm H2O). Tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 in intestine and liver were 2 to 3 times higher with mechanical ventilation than during spontaneous breathing (P<0.05) but similar in plasma and lung. Abdominal edema formation and TNF-α in intestine correlated inversely with abdominal perfusion pressure.

CONCLUSIONS

Mechanical ventilation with positive end-expiratory pressure increases abdominal edema and inflammation in intestine and liver in experimental endotoxemia by increasing systemic capillary leakage and impeding abdominal lymph drainage.

Acute respiratory distress syndrome and multiple organ failure

PURPOSE OF REVIEW

Despite improvements in outcome due to lung protective ventilation strategies using low tidal volumes, the mortality rate from acute respiratory distress syndrome (ARDS) remains unacceptably high, ranging from 34 to 64%. The predominant cause of death in ARDS is not severe hypoxemia, which is one of the defining criteria of ARDS, but multiple organ failure (MOF).

RECENT FINDINGS

In view of the relationship between ARDS and MOF, two different but complementary pathophysiological perspectives will be developed in this article: ARDS as a consequence of MOF, and ARDS as the cause of MOF. This framework may be useful in guiding the development of novel therapeutic strategies that ultimately improve the outcome of ARDS and sepsis patients.

SUMMARY

ARDS is a severe lung disease characterized by a very complex pathophysiology, involving not only the respiratory system but also nonpulmonary distal organs. Elucidation of the pathophysiological mechanisms bi-directionally linking MOF to ARDS appears to be a promising area of research that hopefully will lead to improved outcomes for these devastating conditions.

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.

Definitive care for the critically ill during a disaster: current capabilities and limitations: from a Task Force for Mass Critical Care summit meeting, January 26-27, 2007, Chicago, IL

In the twentieth century, rarely have mass casualty events yielded hundreds or thousands of critically ill patients requiring definitive critical care. However, future catastrophic natural disasters, epidemics or pandemics, nuclear device detonations, or large chemical exposures may change usual disaster epidemiology and require a large critical care response. This article reviews the existing state of emergency preparedness for mass critical illness and presents an analysis of limitations to support the suggestions of the Task Force on Mass Casualty Critical Care, which are presented in subsequent articles. Baseline shortages of specialized resources such as critical care staff, medical supplies, and treatment spaces are likely to limit the number of critically ill victims who can receive life-sustaining interventions. The deficiency in critical care surge capacity is exacerbated by lack of a sufficient framework to integrate critical care within the overall institutional response and coordination of critical care across local institutions and broader geographic areas.

Acute and long-term survival in chronically critically ill surgical patients: a retrospective observational study

INTRODUCTION

Various cohort studies have shown that acute (short-term) mortality rates in unselected critically ill patients may have improved during the past 15 years. Whether these benefits also affect acute and long-term prognosis in chronically critically ill patients is unclear, as are determinants relevant to prognosis.

METHODS

We conducted a retrospective analysis of data collected from March 1993 to February 2005. A cohort of 390 consecutive surgical patients requiring intensive care therapy for more than 28 days was analyzed.

RESULTS

The intensive care unit (ICU) survival rate was 53.6%. Survival rates at one, three and five years were 61.8%, 44.7% and 37.0% among ICU survivors. After adjustment for relevant covariates, acute and long-term survival rates did not differ significantly between 1993 to 1999 and 1999 to 2005 intervals. Acute prognosis was determined by disease severity during ICU stay and by primary diagnosis. However, only the latter was independently associated with long-term prognosis. Advanced age was an independent prognostic determinant of poor short-term and long-term survival.

CONCLUSION

Acute and long-term prognosis in chronically critically ill surgical patients has remained unchanged throughout the past 12 years. After successful surgical intervention and intensive care, long-term outcome is reasonably good and is mainly determined by age and underlying disease.

Time-limited hyporesponsiveness to inhaled nitric oxide and pulmonary phosphodiesterase activity in endotoxemic rats

In acute lung injury (ALI) pulmonary hyporesponsiveness to inhaled nitric oxide (iNO) still represents an unresolved clinical challenge. In septic ALI-patients the incidence of hyporesponsiveness to iNO is increased; therefore, endotoxemia appears to play a major role. Experimental data suggest that endotoxemia, e.g., induced by lipopolysaccharides (LPS), contribute to the hyporesponsiveness to iNO. Guanosine 3',5'-cyclic monophosphate (cGMP) is metabolized by phosphodiesterases (PDE). The role of PDE in reduced pulmonary vascular response in experimental endotoxemia is still not known. Here, we hypothesized that PDE activity modulates initial pulmonary responsiveness to iNO in ALI following systemic endotoxin exposure. Rats were treated with LPS or used as controls. Lungs were isolated-perfused 0-36 h after LPS injection and the synthetic thromboxane analogue U46619 was added to increase pulmonary artery pressure by 6-8 mmHg (n = 47). Then, the pulmonary vasodilatory response to 3 doses of iNO (0.4, 4 and 40 ppm) was measured. Furthermore, lungs were prepared as described previously, and 2, 10, and 18 h after LPS the change in pulmonary artery pressure in response to two different inhibitors of PDE, one of which is PDE sensitive (8-Br-cGMP) and one is PDE stable (8-pCPT-cGMP), was determined (n = 43). Serum nitrite/nitrate levels started to increase 4 h after LPS, with a maximum at 18 h. In contrast, decreased pulmonary vasoreactivity in response to iNO developed as early as 2 h later and remained depressed up to 18 h. The pulmonary vasoreactivity to the PDE-sensitive 8-Br-cGMP after LPS-stimulation was lower than that in lungs treated with the PDE-stable 8-pCPT-cGMP. In rats pretreated with LPS, hyporesponsiveness of pulmonary vessels to iNO is time-limited and associated with increased serum nitrite/nitrate levels, and appears to be attributed in part to increased pulmonary PDE activity.

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.

Epidemiology of Acute Respiratory Failure and Mechanical Ventilation

Acute respiratory failure, and the need for mechanical ventilation, remains one of the most common reasons for admission to the intensive care unit (ICU). The burden of acute respiratory failure is high in terms of mortality and morbidity as well as the cost of its principal treatment, mechanical ventilation. Very few epidemiologic studies have evaluated the prevalence and outcome of acute respiratory failure and mechanical ventilation in general. Most of the published literature has focused on specific forms of acute respiratory failure, particularly acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). In this chapter, we provide a brief review of the pathophysiology of acute respiratory failure, its definition and classification, and then present the incidence and outcomes of specific forms of acute respiratory failure from epidemiologic studies.

Epidemiology of Acute Respiratory Failure and Mechanical Ventilation

Acute respiratory failure, and the need for mechanical ventilation, remains one of the most common reasons for admission to the intensive care unit (ICU). The burden of acute respiratory failure is high in terms of mortality and morbidity as well as the cost of its principal treatment, mechanical ventilation. Very few epidemiologic studies have evaluated the prevalence and outcome of acute respiratory failure and mechanical ventilation in general. Most of the published literature has focused on specific forms of acute respiratory failure, particularly acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). In this chapter, we provide a brief review of the pathophysiology of acute respiratory failure, its definition and classification, and then present the incidence and outcomes of specific forms of acute respiratory failure from epidemiologic studies.

Nonpulmonary organ dysfunction and its impact on outcome in patients with acute respiratory failure

PURPOSES

This study aimed to define the prevalence, severity, and progression of nonpulmonary organ dysfunction, and its impact on outcome in patients with acute respiratory failure (ARF) at a respiratory ICU of a tertiary referral hospital in northern India.

METHODS

Daily patient data were collected on 711 adult patients with ARF to calculate component and total nonpulmonary sequential organ failure assessment (SOFA) scores. Hospital survival was the main outcome measure. Multiple logistic regression modeling was conducted to assess contribution of incremental dysfunction of various nonpulmonary organ systems to mortality. Kaplan-Meier curves were drawn to assess temporal trends in survival, and group comparisons were based on log-rank test. Cox proportional hazard modeling was performed to define hazards of earlier mortality. Discrimination was evaluated using receiver operating characteristic (ROC) curves.

RESULTS

Four hundred seventy-five patients (66.8%) had one or more nonpulmonary organ dysfunctions at hospital admission. The overall hospital mortality rate was 33.9%. Hospital survival rates and median survival declined steadily as the number of organs involved increased. Admission, maximum, and DeltaSOFA scores were significantly higher in nonsurvivors. Increasing baseline cardiovascular and neurologic SOFA scores, and corresponding DeltaSOFA scores, were associated with progressively higher odds of hospital mortality, as well as increasing hazard for earlier mortality after adjustment for etiology of respiratory failure. Maximum nonpulmonary SOFA score was the best discriminator in predicting mortality (area under ROC curve, 0.767).

CONCLUSION

Baseline and new-onset nonpulmonary organ dysfunction significantly influences hospital survival in patients with ARF.

Secular trends in mortality associated with new therapeutic strategies in surgical critical illness

BACKGROUND

Since 1999 randomized controlled trials have shown that new therapeutic strategies, such as strict glycemic control, increased use of noninvasive ventilation and of lung-protective ventilation, and early goal-oriented shock therapy, may reduce mortality in selected groups of critically ill patients. Whether these benefits can be translated to a surgical clinical setting is unclear. We wanted to evaluate longitudinally the successive routine implementation of new therapeutic measures and its effect on postsurgical patients admitted to the intensive care unit.

METHODS

We performed a retrospective analysis on data collected prospectively from March 1, 1993 through February 28, 2005.

RESULTS

A cohort of 1,802 consecutive cases requiring intensive care therapy for more than 4 days was analyzed. A significant decrease in mortality was observed in the last years of the study. With adjustment for relevant covariates, treatment after the implementation of new therapeutic strategies was identified as an independent factor linked with a reduced risk of death (odds ratio [OR] .518; 95% confidence interval [CI] .337-.796), whereas older age (OR 1.030; 95% CI 1.015-1.045), a high severity score on admission (OR 1.155; 95% CI 1.113-1.198) or during intensive care unit stay (OR 1.187; 95% CI 1.145-1.231), a high number of failing organs (OR 1.918; 95% CI 1.635-2.250), and peritonitis (OR 3.277; 95% CI 2.046-5.246) were independently associated with death.

CONCLUSIONS

Implementing of a variety of new therapeutic measures into routine care of critically ill surgical patients was associated with improved survival after 2001.

Acute lung injury and the acute respiratory distress syndrome: a clinical review

Acute respiratory distress syndrome and acute lung injury are well defined and readily recognised clinical disorders caused by many clinical insults to the lung or because of predispositions to lung injury. That this process is common in intensive care is well established. The mainstay of treatment for this disorder is provision of excellent supportive care since these patients are critically ill and frequently have coexisting conditions including sepsis and multiple organ failure. Refinements in ventilator and fluid management supported by data from prospective randomised trials have increased the methods available to effectively manage this disorder.

[Trends in surgical intensive care. Experience in one centre over 12 years]

BACKGROUND

For critically ill medical patients until the year 2000, increases in patient age and severity of disease but also acute prognosis have been described. Since then, further improvement appears possible. Several controlled studies have recently demonstrated that acute mortality may be further lowered by new adjuvant therapies such as aggressive glycemic control. However, it is still unknown whether demographic changes and progress in intensive care can be reproduced in surgical critically ill patients outside of a controlled trial setting.

METHODS

We performed a retrospective, observational cohort study using data prospectively collected from the surgical intensive care unit (ICU) of the LMU Department of Surgery in Munich, Germany, Grosshadern Campus, from March 1 1993 through February 28 2005. Since 1999 we have successively introduced a variety of new therapies to daily routine. A cohort of 5,495 patients was analysed.

RESULTS

We identified reduced ICU mortality during the observation period, although age rose simultaneously and disease severity remained constant. Results from multivariate analysis suggest that improvements in prognosis essentially result from the implementation of new therapies after 2001. After adjusting for more than 20 covariables, treatment received after 2001 was identified as an independent factor linked with reduced risk of death.

CONCLUSIONS

General demographic trends and progress in intensive care can be demonstrated also in unselected surgical cohorts. Furthermore, the results here confirm the efficacy of new therapeutic modifications in routine therapy.

Positive-pressure ventilation equipment for mass casualty respiratory failure

In the event of an influenza pandemic, patients with severe acute respiratory failure (ARF) due to influenza will require positive-pressure ventilation (PPV) in order to survive. In countries with widely available critical care services, PPV is delivered almost exclusively through use of full-feature mechanical ventilators in intensive care units (ICUs) or specialized hospital wards. But the supply of these ventilators is limited even during the normal course of hospital functioning. Purchasing and maintaining additional full-feature mechanical ventilators to be held in reserve and used only during mass casualty events is too expensive to allow the stockpiling of such equipment. Consequently, planning and preparedness efforts to respond to a severe influenza pandemic have stimulated consideration of limited-feature, less-expensive ventilation devices to augment traditional PPV capacity. This article offers guidance to authorities charged with preparing for mass casualty PPV in deciding which PPV equipment would be adequate for ventilating patients for days, weeks, or even months during a medical catastrophe.

Augmentation of hospital critical care capacity after bioterrorist attacks or epidemics: recommendations of the Working Group on Emergency Mass Critical Care

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

Implementation of a tight glycaemic control protocol using a web-based insulin dose calculator

We describe the implementation of a glucose control protocol supported by a web-based insulin dose calculator in a 16-bedded intensive care unit. The protocol was introduced and then modified after 15 months' use. Glucose concentrations were retrospectively reviewed and compared for the 9-month period before introduction of the protocol (288 patients), for 15 months after its introduction (502 patients) and for a further 5 months after its modification to increase insulin dose (101 patients). The mean (SD) blood glucose concentrations decreased from 7.3 (1.8) mmol.l(-1) to 6.6 (1.6) mmol.l(-1) and then to 6.2 (1.3) mmol.l(-1). The proportion of values < 8.0 mmol.l(-1) increased from 69% to 81% and then to 89%. Blood glucose concentrations were increased by the use of intravenous nutrition and by vasoactive drugs but not by the administration of propofol. The odds ratio [95% CI] for death for glucose values > 8.0 mmol.l(-1) was 2.10 [1.19-3.73] compared to values < 6.1 mmol.l(-1). However, patient mortality remained constant during the study. Glycaemic control was improved outside a research setting using a protocol supported by a web-based insulin dose calculator.

Acute respiratory distress syndrome: a historical perspective

Though well described even in ancient writings, the acute respiratory distress syndrome (ARDS) gained major medical attention with the availability of mechanical ventilation and establishment of intensive care units. In the 50 years since this beginning there have been remarkable advances in the understanding of the etiology, physiology, histology, and epidemiology of this often lethal complication of common human maladies. Until recently, improvements in outcome have mainly followed improvements in intensive care unit operation and their associated life support systems, and have not come through discoveries made in the course of prospective randomized trials. In spite of the remarkable increase in research focused on ARDS, there remain a large number of unanswered clinical questions that are potentially extremely important with regard to short-term morbidity as well as long-term outcome. The ARDS Clinical Trials Network study of tidal volume has proven that randomized trials in ARDS with positive results are possible even when using difficult primary outcome measures such as mortality or ventilator-free days. Therefore, the rich combination of new trial strategies, potential treatments, experienced investigators, and increasingly standardized routine care set the stage for rapid advances to be made in the short- and long-term outcomes of this devastating syndrome.

Causes and timing of death in patients with ARDS

BACKGROUND

Since the early 1980s, case fatality of patients with ARDS has decreased, and explanations are unclear.

DESIGN AND METHODS

Using identical definitions of ARDS and organ failure, we analyzed consecutive cohorts of patients meeting syndrome criteria at our institution in 1982 (n = 46), 1990 (n = 112), 1994 (n = 99), and 1998 (n = 205) to determine causes and timing of death.

RESULTS

Overall case fatality has decreased from 68% in 1981-1982 to a low of 29% in 1996, plateauing since the mid-1990s (p = 0.001 for trend). Sepsis syndrome with multiple organ failure remains the most common cause of death (30 to 50%), while respiratory failure causes a small percentage (13 to 19%) of deaths. The distribution of causes of death has not changed over time. There was no change in the timing of death during the study periods: 26 to 44% of deaths occurred early (< 72 h after ARDS onset), and 56 to 74% occurred late (> 72 h after ARDS onset). However, the increased survival over the past 2 decades is entirely accounted for by patients who present with trauma and other risk factors for their ARDS, while survival for those patients whose risk factor is sepsis has not changed. Additionally, withdrawal of life support in these patients is now occurring at our institution significantly more frequently than in the past, and median time until death has decreased in patients who have support withdrawn.

CONCLUSIONS

While these results do not explain the overall case fatality decline in ARDS, they do indicate that sepsis syndrome remains the leading cause of death and suggest that future therapies to improve survival be targeted at reducing the complications of sepsis.

[Management of acute pulmonary failure: diagnostics-ventilation-withdrawal]

Acute pulmonary failure by definition excludes cardiac insufficiency as the pathogenetic mechanism involved in the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). The systemic inflammatory reaction underlying acute pulmonary failure has many etiological causes. One of the most important trigger mechanisms is sepsis. In the realm of cardiac intensive care medicine, the systemic inflammatory reaction is observed in conjunction with assist systems, during extracorporeal circulation, or in the course of cardiogenic shock. In the end, even mechanical ventilation itself can elicit an inflammatory reaction and result in pulmonary failure through ventilator-associated lung injury. Knowledge of the mechanisms has led to the concept of protective ventilation, which exerts both prophylactic and therapeutic effects. Protective ventilation is an integral part of a bundle of therapeutic intensive care measures. Both constitute the essence of management of acute pulmonary failure.

Cellular infiltrates and injury evaluation in a rat model of warm pulmonary ischemia-reperfusion

Introduction

Beside lung transplantation, cardiopulmonary bypass, isolated lung perfusion and sleeve resection result in serious pulmonary ischemia–reperfusion injury, clinically known as acute respiratory distress syndrome. Very little is known about cells infiltrating the lung during ischemia–reperfusion. Therefore, a model of warm ischemia–reperfusion injury was applied to differentiate cellular infiltrates and to quantify tissue damage.

Methods

Fifty rats were randomized into eight groups. Five groups underwent warm ischemia for 60 min followed by 30 min and 1–4 hours of warm reperfusion. An additional group was flushed with the use of isolated lung perfusion after 4 hours of reperfusion. One of two sham groups was also flushed. Neutrophils and oedema were investigated by using samples processed with hematoxylin/eosin stain at a magnification of ×500. Immunohistochemistry with antibody ED-1 (magnification ×250) and antibody 1F4 (magnification ×400) was applied to visualize macrophages and T cells. TdT-mediated dUTP nick end labelling was used for detecting apoptosis. Statistical significance was accepted at P < 0.05.

Results

Neutrophils were increased after 30 min until 4 hours of reperfusion as well as after flushing. A doubling in number of macrophages and a fourfold increase in T cells were observed after 30 min until 1 and 2 hours of reperfusion, respectively. Apoptosis with significant oedema in the absence of necrosis was seen after 30 min to 4 hours of reperfusion.

Conclusions

After warm ischemia–reperfusion a significant increase in infiltration of neutrophils, T cells and macrophages was observed. This study showed apoptosis with serious oedema in the absence of necrosis after all periods of reperfusion.