Marco González

Evolution of Mortality over Time in Patients Receiving Mechanical Ventilation

RATIONALE Baseline characteristics and management have changed over time in patients requiring mechanical ventilation; however, the impact of these changes on patient outcomes is unclear. OBJECTIVES To estimate whether mortality in mechanically ventilated patients has changed over time. METHODS Prospective cohort studies conducted in 1998, 2004, and 2010, including patients receiving mechanical ventilation for more than 12 hours in a 1-month period, from 927 units in 40 countries. To examine effects over time on mortality in intensive care units, we performed generalized estimating equation models. MEASUREMENTS AND MAIN RESULTS We included 18,302 patients. The reasons for initiating mechanical ventilation varied significantly among cohorts. Ventilatory management changed over time (P < 0.001), with increased use of noninvasive positive-pressure ventilation (5% in 1998 to 14% in 2010), a decrease in tidal volume (mean 8.8 ml/kg actual body weight [SD = 2.1] in 1998 to 6.9 ml/kg [SD = 1.9] in 2010), and an increase in applied positive end-expiratory pressure (mean 4.2 cm H2O [SD = 3.8] in 1998 to 7.0 cm of H2O [SD = 3.0] in 2010). Crude mortality in the intensive care unit decreased in 2010 compared with 1998 (28 versus 31%; odds ratio, 0.87; 95% confidence interval, 0.80-0.94), despite a similar complication rate. Hospital mortality decreased similarly. After adjusting for baseline and management variables, this difference remained significant (odds ratio, 0.78; 95% confidence interval, 0.67-0.92). CONCLUSIONS Patient characteristics and ventilation practices have changed over time, and outcomes of mechanically ventilated patients have improved. Clinical trials registered with www.clinicaltrials.gov (NCT01093482).

Outcome of mechanically ventilated patients who require a tracheostomy

Objective:To estimate the prevalence of, the risk factors associated with, and the outcome of tracheostomy in a heterogeneous population of mechanically ventilated patients. Design:Prospective, observational cohort study. Setting:A total of 361 intensive care units from 12 countries. Patients:A cohort of 5,081 patients mechanically ventilated for >12 hrs. Interventions:None. Measurements and Main Results:A total of 546 patients (10.7%) had a tracheostomy during their stay in the intensive care unit. Tracheostomy was performed at a median time of 12 days (interquartile range, 7–17) from the beginning of mechanical ventilation. Variables associated with the performance of tracheostomy were duration of mechanical ventilation, need for reintubation, and neurologic disease as the primary reason of mechanical ventilation. The intensive care unit stay of patients with or without tracheostomy was a median of 21 days (interquartile range, 12–32) vs. 7 days (interquartile range, 4–12; p < .001), respectively, and the hospital stay was a median 36 days (interquartile range, 23–53) vs. 15 days (interquartile range, 8–26; p < .001), respectively. Adjusting by other variables, tracheostomy was independently related with survival in the intensive care unit (odds ratio, 2.22; 95% confidence interval, 1.72–2.86). Mortality in the hospital was similar in both groups (39% vs. 40%, p = .65). Conclusions:Tracheostomy is a common surgical procedure in the intensive care unit that is associated with a lower mortality in the unit but with a longer stay and a similar mortality in the hospital than in patients without tracheostomy.

Airway pressures, tidal volumes, and mortality in patients with acute respiratory distress syndrome

Objective:To determine the usual practice for setting tidal volume and other ventilatory parameters in patients with acute respiratory distress syndrome (ARDS) in the late 1990s and to determine the independent effects of these practices on intensive care unit mortality. Design:Subanalysis of a prospective observational study. Multivariable logistic regression was used to analyze the effects of ventilatory management on mortality. Setting:A total of 361 intensive care units in 20 countries in March 1998. Patients:A total of 467 mechanically ventilated patients with ARDS. Interventions:None. Measurements and Main Results:The mean tidal volume used in the first week of ARDS was 8.8 mL/kg measured body weight, and there was great variability in these tidal volumes (sd = 2.0). Tidal volumes were significantly lower in patients with (n = 265) than without (n = 202) a recorded plateau pressure (8.6 vs. 9.1 mL/kg, p = .01). The overall intensive care unit mortality rate was 60.2%. In addition to the strong influence of organ failures and higher levels of inspired oxygen, late-onset ARDS (onset after >48 hrs of mechanical ventilation; odds ratio, 2.09) was independently associated with mortality. In addition, lower levels of positive end-expiratory pressure were independently associated with higher mortality (odds ratio, 0.91; 1 cm of H2O increments). Neither inspiratory pressures nor tidal volumes were independently associated with mortality, and there was no evidence of increased mortality with the use of lower inspiratory pressures. Conclusions:This descriptive study demonstrated considerable interpatient variability in tidal volumes during the study period. In addition to traditional prognostic indicators, timing of ARDS onset and the use of low levels of positive end-expiratory pressure or no positive end-expiratory pressure during the first week may adversely influence outcome in ARDS patients.

Characteristics and Outcomes of Ventilated Patients According to Time to Liberation from Mechanical Ventilation

RATIONALE A new classification of patients based on the duration of liberation of mechanical ventilation has been proposed. OBJECTIVES To analyze outcomes based on the new weaning classification in a cohort of mechanically ventilated patients. METHODS Secondary analysis included 2,714 patients who were weaned and underwent scheduled extubation from a cohort of 4,968 adult patients mechanically ventilated for more than 12 hours. MEASUREMENTS AND MAIN RESULTS Patients were classified according to a new weaning classification: 1,502 patients (55%) as simple weaning,1,058 patients (39%) as difficult weaning, and 154 (6%) as prolonged weaning.Variables associated with prolonged weaning(.7d)were: severity at admission (odds ratio [OR] per unit of Simplified Acute Physiology Score II, 1.01; 95% confidence interval [CI], 1.001–1.02), duration of mechanical ventilation before first attempt of weaning (OR per day, 1.10; 95% CI, 1.06–1.13), chronic pulmonary disease other than chronic obstructive pulmonary disease (OR,13.23; 95% CI, 3.44–51.05), pneumonia as the reason to start mechanical ventilation (OR, 1.82; 95% CI, 1.07–3.08), and level of positive end-expiratory pressure applied before weaning (OR per unit,1.09; 95% CI, 1.04–1.14). The prolonged weaning group had a nonsignificant trend toward a higher rate of reintubation (P ¼ 0.08),tracheostomy (P ¼ 0.15), and significantly longer length of stay and higher mortality in the intensive care unit (OR for death, 1.97;95%CI, 1.17–3.31). The adjusted probability of death remained constant until Day 7, at which point it increased to 12.1%.

Outcome of reintubated patients after scheduled extubation

PURPOSE The main objective of study was to evaluate the outcome of patients who require reintubation after elective extubation. MATERIALS AND METHODS This is an observational, prospective cohort study including mechanically ventilated patients who passed successfully a spontaneous breathing trial. Patients were observed for 48 hours after extubation. During this time, reintubation or use of noninvasive positive pressure ventilation was considered as a failure. Reintubated patients were followed after the reintubation to register complications and outcome. RESULTS A total of 1,152 extubated patients were included in the analysis. Three hundred thirty-six patients (29%) met the criteria for extubation failure. Extubation failure was independently associated with mortality (odds ratio, 3.29; 95% confidence interval, 2.19-4.93). One hundred eighty patients (16% of overall cohort) required reintubation within 48 hours after extubation. Median time from extubation to reintubation was 13 hours (interquartile range, 6-24 hours). Reintubation was independently associated with mortality (odds ratio, 5.18; 95% confidence interval, 3.38-7.94; P < .001). Higher mortality of reintubated patients was due to the development of complications after the reintubation. CONCLUSIONS In a large cohort of scheduled extubated patients, one third of patients developed extubation failure, of whom half needed reintubation. Reintubation was associated with increased mortality due to the development of new complications after reintubation.

Influence of body mass index on outcome of the mechanically ventilated patients

Background There are limited data on the impact of body mass index on outcomes in mechanically ventilated patients. Methods Secondary analysis of a cohort including 4698 patients mechanically ventilated. Patients were screened daily for management of mechanical ventilation, complications (acute respiratory distress syndrome, sepsis, ventilator associated pneumonia, barotrauma), organ failure (cardiovascular, respiratory, renal, hepatic, haematological) and mortality in the intensive care unit. To estimate the impact of body mass index on acute respiratory distress syndrome and mortality, the authors constructed models using generalised estimating equations (GEE). Results Patients were evaluated based on their body mass index: 184 patients (3.7%) were underweight, 1995 patients (40%) normal weight, 1781 patients (35.8%) overweight, 792 patients (15.9%) obese and 216 patients (4.3%) severely obese. Severely obese patients were more likely to receive low tidal volume based on actual body weight but high volumes based on predicted body weight. In obese patients, the authors observed a higher incidence of acute respiratory distress syndrome and acute renal failure. After adjustment, the body mass index was significantly associated with the development of acute respiratory distress syndrome: compared with normal weight; OR 1.69 (95% CI 1.07 to 2.69) for obese and OR 2.38 (95% CI 1.15 to 4.89) for severely obese. There were no differences in outcomes (duration of mechanical ventilation, length of stay and mortality in intensive care unit and hospital) based on body mass index categories. Conclusions In this cohort, obese patients were more likely to have significant complications but there were no associations with increased mortality.

Management and outcome of mechanically ventilated neurologic patients.

Objective: To describe and compare characteristics, ventilatory practices, and associated outcomes among mechanically ventilated patients with different types of brain injury and between neurologic and nonneurologic patients. Design: Secondary analysis of a prospective, observational, and multicenter study on mechanical ventilation. Setting: Three hundred forty-nine intensive care units from 23 countries. Patients: We included 552 mechanically ventilated neurologic patients (362 patients with stroke and 190 patients with brain trauma). For comparison we used a control group of 4,030 mixed patients who were ventilated for nonneurologic reasons. Interventions: None. Measurements and Main Results: We collected demographics, ventilatory settings, organ failures, and complications arising during ventilation and outcomes. Multivariate logistic regression analysis was performed with intensive care unit mortality as the dependent variable. At admission, a Glasgow Coma Scale score ≤8 was observed in 68% of the stroke, 77% of the brain trauma, and 29% of the nonneurologic patients. Modes of ventilation and use of a lung-protective strategy within the first week of mechanical ventilation were similar between groups. In comparison with nonneurologic patients, patients with neurologic disease developed fewer complications over the course of mechanical ventilation with the exception of a higher rate of ventilator-associated pneumonia in the brain trauma cohort. Neurologic patients showed higher rates of tracheotomy and longer duration of mechanical ventilation. Mortality in the intensive care unit was significantly (p < .001) higher in patients with stroke (45%) than in brain trauma (29%) and nonneurologic disease (30%). Factors associated with mortality were: stroke (in comparison to brain trauma), Glasgow Coma Scale score on day 1, and severity at admission in the intensive care unit. Conclusions: In our study, one of every five mechanically ventilated patients received this therapy as a result of a neurologic disease. This cohort of patients showed a higher mortality rate than nonneurologic patients despite a lower incidence of extracerebral organ dysfunction.

Airway pressure release ventilation versus assist-control ventilation: a comparative propensity score and international cohort study

PurposeTo compare characteristics and clinical outcomes of patients receiving airway pressure release ventilation (APRV) or biphasic positive airway pressure (BIPAP) to assist-control ventilation (A/C) as their primary mode of ventilatory support. The objective was to estimate if patients ventilated with APRV/BIPAP have a lower mortality.MethodsSecondary analysis of an observational study in 349 intensive care units from 23 countries. A total of 234 patients were included who were ventilated only with APRV/BIPAP and 1,228 patients who were ventilated only with A/C. A case-matched analysis according to a propensity score was used to make comparisons between groups.ResultsIn logistic regression analysis, the most important factor associated with the use of APRV/BIPAP was the country (196 of 234 patients were from German units). Patients with coma or congestive heart failure as the reason to start mechanical ventilation, pH <7.15 prior to mechanical ventilation, and patients who developed respiratory failure (SOFA score >2) after intubation with or without criteria of acute respiratory distress syndrome were less likely to be ventilated with APRV/BIPAP. In the case-matched analysis there were no differences in outcomes, including mortality in the intensive care unit, days of mechanical ventilation or weaning, rate of reintubation, length of stay in the intensive care unit or hospital, and mortality in the hospital.ConclusionsIn this study, the APRV/BIPAP ventilation mode is being used widely across many causes of respiratory failure, but only in selected geographic areas. In our patient population we could not demonstrate any improvement in outcomes with APRV/BIPAP compared with assist-control ventilation.

EARLY AND SMALL CHANGES IN SERUM CREATININE CONCENTRATIONS ARE ASSOCIATED WITH MORTALITY IN MECHANICALLY VENTILATED PATIENTS

Emerging evidence suggests that minor changes in serum creatinine concentrations are associated with increased hospital mortality rates. However, whether serum creatinine concentration (SCr) on admission and its change are associated with an increased mortality rate in mechanically ventilated patients is not known. We have conducted an international, prospective, observational cohort study enrolling adult intensive care unit patients under mechanical ventilation (MV). Recursive partitioning was used to determine the values of SCr at the start of MV (SCr0) and the change in SCr ([&Dgr;SCr] defined as the maximal difference between the value at start of MV [day 0] and the value on MV day 2 at 8:00 am) that best discriminate mortality. In-hospital mortality, adjusted by a proportional hazards model, was the primary outcome variable. A total of 2,807 patients were included; median age was 59 years and median Simplified Acute Physiology Score II was 44. All-cause in-hospital mortality was 44%. The variable that best discriminated outcome was a SCr0 greater than 1.40 mg/dL (mortality, 57% vs. 36% for patients with SCr0 ≤1.40 mg/dL, P < 0.001). Among patients with SCr0 less than or equal to 1.40 mg/dL, &Dgr;SCr greater than 0.31 discriminated mortality (56% vs. 34%, P < 0.001). In multivariate analysis, geographic area, advanced age, severity of illness, reason for MV, and cardiovascular and hepatic failure were also associated with mortality. Our study suggests that SCr0 greater than 1.40 mg/dL and, in patients with low baseline SCr, a &Dgr;SCr greater than 0.31 are predictors of in-hospital mortality in mechanically ventilated patients.

Outcomes of Patients Ventilated With Synchronized Intermittent Mandatory Ventilation With Pressure Support: A Comparative Propensity Score Study

BACKGROUND Few data are available regarding the benefits of one mode over another for ventilatory support. We set out to compare clinical outcomes of patients receiving synchronized intermittent mandatory ventilation with pressure support (SIMV-PS) compared with assist-control (A/C) ventilation as their primary mode of ventilatory support. METHODS This was a secondary analysis of an observational study conducted in 349 ICUs from 23 countries. A propensity score stratified analysis was used to compare 350 patients ventilated with SIMV-PS with 1,228 patients ventilated with A/C ventilation. The primary outcome was in-hospital mortality. RESULTS In a logistic regression model, patients were more likely to receive SIMV-PS if they were from North America, had lower severity of illness, or were ventilated postoperatively or for trauma. SIMV-PS was less likely to be selected if patients were ventilated because of asthma or coma, or if they developed complications such as sepsis or cardiovascular failure during mechanical ventilation. In the stratified analysis according to propensity score, we did not find significant differences in the in-hospital mortality. After adjustment for propensity score, overall effect of SIMV-PS on in-hospital mortality was not significant (odds ratio, 1.04; 95% CI, 0.77-1.42; P = .78). CONCLUSIONS In our cohort of ventilated patients, ventilation with SIMV-PS compared with A/C did not offer any advantage in terms of clinical outcomes, despite treatment-allocation bias that would have favored SIMV-PS.