Weaning from mechanical ventilation in intensive care units across 50 countries (WEAN SAFE): a multicentre, prospective, observational cohort study

BACKGROUND

Current management practices and outcomes in weaning from invasive mechanical ventilation are poorly understood. We aimed to describe the epidemiology, management, timings, risk for failure, and outcomes of weaning in patients requiring at least 2 days of invasive mechanical ventilation.

METHODS

WEAN SAFE was an international, multicentre, prospective, observational cohort study done in 481 intensive care units in 50 countries. Eligible participants were older than 16 years, admitted to a participating intensive care unit, and receiving mechanical ventilation for 2 calendar days or longer. We defined weaning initiation as the first attempt to separate a patient from the ventilator, successful weaning as no reintubation or death within 7 days of extubation, and weaning eligibility criteria based on positive end-expiratory pressure, fractional concentration of oxygen in inspired air, and vasopressors. The primary outcome was the proportion of patients successfully weaned at 90 days. Key secondary outcomes included weaning duration, timing of weaning events, factors associated with weaning delay and weaning failure, and hospital outcomes. This study is registered with ClinicalTrials.gov, NCT03255109.

FINDINGS

Between Oct 4, 2017, and June 25, 2018, 10 232 patients were screened for eligibility, of whom 5869 were enrolled. 4523 (77·1%) patients underwent at least one separation attempt and 3817 (65·0%) patients were successfully weaned from ventilation at day 90. 237 (4·0%) patients were transferred before any separation attempt, 153 (2·6%) were transferred after at least one separation attempt and not successfully weaned, and 1662 (28·3%) died while invasively ventilated. The median time from fulfilling weaning eligibility criteria to first separation attempt was 1 day (IQR 0-4), and 1013 (22·4%) patients had a delay in initiating first separation of 5 or more days. Of the 4523 (77·1%) patients with separation attempts, 2927 (64·7%) had a short wean (≤1 day), 457 (10·1%) had intermediate weaning (2-6 days), 433 (9·6%) required prolonged weaning (≥7 days), and 706 (15·6%) had weaning failure. Higher sedation scores were independently associated with delayed initiation of weaning. Delayed initiation of weaning and higher sedation scores were independently associated with weaning failure. 1742 (31·8%) of 5479 patients died in the intensive care unit and 2095 (38·3%) of 5465 patients died in hospital.

INTERPRETATION

In critically ill patients receiving at least 2 days of invasive mechanical ventilation, only 65% were weaned at 90 days. A better understanding of factors that delay the weaning process, such as delays in weaning initiation or excessive sedation levels, might improve weaning success rates.

FUNDING

European Society of Intensive Care Medicine, European Respiratory Society.

P3545Association between diastolic dysfunction and two-year survival in heart failure patients with mid-range or reduced left ventricular ejection fraction

Background

Extensive studies have demonstrated prognostic impact of echocardiographic defined diastolic dysfunction (DD) in patients with preserved as well as reduced left ventricular ejection fraction (LVEF). Nevertheless, it remains controversial whether evaluation of DD could provide additional prognostic information in heart failure (HF) patients with impaired systolic function. The purpose of present study, therefore, is to investigate the prognostic impact of echocardiography-defined DD on survival in HF patients hospitalized in our centre from 2009 to 2017 with mid-range LVEF (HFmrEF, LVEF 41–49%) and reduced LVEF (HFrEF, LVEF<40%).

Methods

A total of 2018 patients with echocardiography-evidenced LVEF<50% and hospitalized in our centre between July 2009 to December 2017 were included. Baseline demographic and clinical data were obtained by reviewing the medical records. All patients subsequently completed a median clinical follow-up of 24 (IQR 13–36) months by medical record review or telephone interview. The primary endpoint was all-cause mortality or heart transplantation (HTx). Patients were divided into mild, moderate and severe DD according to recent guidelines.

Results

The mean age was 69±13 years in the HFmrEF group and 68±13 years in the HFrEF group. All-cause mortality/HTx rate was significantly higher in the HFrEF (all-cause death n=318 and HTx n=11, 30.9%) group than in patients with HFmrEF (all-cause death n=235 and HTx n=2, 24.9%, P=0.003). All-cause mortality/HTx rate increased in proportion to DD severity in HFmrEF patients: 17.1% (54/315) in the mild DD group, 25.4% (115/452) in the moderate DD group, and 37.0% (68/184) in the severe DD group (P<0.001) and in HFrEF patients: 18.9% (43/228) in the mild DD group, 30.3% (146/482) in the moderate DD group, and 39.2% (140/357) in the severe DD group (P<0.001). Multivariable Cox regression analysis showed that Doppler parameter early-diastolic mitral inflow velocity to septal mitral annular velocity ratio (E/E') >14 (HR 1.41, 95% CI 1.06–1.89, P=0.020) and peak tricuspid regurgitation velocity (TRVmax) >2.8m/s (HR 1.75, 95% CI 1.33–2.29, P<0.001) were independent determinants of all-cause mortality/HTx in patients with HFmrEF; while E/E'>14 (HR 1.48, 95% CI 1.08–2.04, P=0.015) remained as an independent determinant of all-cause mortality/HTx in patients with HFrEF after adjustment for clinical and other echocardiographic confounders. Besides DD-related parameters, after adjustment with age and sex, lower tricuspid and mitral annular plane systolic excursions (TAPSE and MAPSE) were also closely related to higher mortality/HTx rate in both HFmrEF and HFrEF patients.

Figure 1. Kaplan-Meier curves

Conclusion

Our results indicate that all-cause mortality/HTx rate increases in proportion to DD severity in both HFmrEF and HFrEF patients.

Speciation of selenium in the mammalian organism

As almost all of the selenium present in the mammalian organism is protein-bound, speciation is mostly concerned with the determination of the different selenium-containing proteins. Information on their distribution and their concentrations in the different tissues of the rat was obtained by means of tracer procedures which, after application of 75Se-selenite with a very high specific activity to selenium-depleted animals and electrophoretic separation of the labelled proteins, allow the determination of these compounds in the pmol to fmos range. A method was developed for the determination of selenocysteine and selenomethionine in the selenium-containing proteins. The identification of specific selenoproteins was achieved by analysis of their selenoamino acid residues and by studies on their characteristics and possible biological functions. This is being followed by the development of methods for the quantitative analysis of the selenoproteins in questions in the tissues of animals and man. In this paper the strategies and procedures used in the identification, characterization and determination of the selenium species present in the mammalian organism will be discussed.

Identification of selenocysteine and selenomethionine in protein hydrolysates by high-performance liquid chromatography of their o-phthaldialdehyde derivatives

A method for the identification of selenocysteine and selenomethionine in protein hydrolysates was developed. The proteins were subjected to acid hydrolysis after they had been carboxymethylated to prevent decomposition of selenocysteine during this process. After precolumn derivatization of the amino acids with o-phthaldialdehyde, the hydrolysate was chromatographed on C18 columns. The selenoamino acids were detected either by the fluorescence of their o-phthaldialdehyde derivatives (detection limit 30 pmol for selenomethionine and 170 pmol for selenocysteine) or by selenium determination in the eluate using atomic absorption spectrometry (detection limit 0.3 pmol) or, with 75Se-labelled compounds, the measurement of the tracer activity. With the latter procedure the detection limit, which depends on the specific activity of the Se tracer, could be decreased to the femtomole range. The method was successfully applied to the identification of selenocysteine in several newly found mammalian selenium-containing proteins.

Two new selenoproteins found in the prostatic glandular epithelium and in the spermatid nuclei

After labeling of rats in vivo with 75Se and protein separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis more than 25 Se-containing bands could be distinguished. Of those proteins which were detected only in certain compartments and might therefore have tissue-specific functions, two were chosen for detailed investigation. A 15 kDa-protein was found in the prostatic epithelium where it accounted for about two thirds of the protein-bound 75Se. It was mainly present in the cytosol but was not released into the prostatic secretion. After gel chromatography it was found in the fraction which contained proteins with molecular masses of about 300 kDa. Using two-dimensional electrophoresis a pI-value of about 4.5 was determined. In the testis a specific Se-containing 34 kDa-protein was observed which appeared after the onset of puberty. It was localized in the spermatid nuclei where it contained about 80% of the Se tracer present and was found to be bound to the DNA. After extraction it partly disintegrated into a 20 kDa-protein. Both compounds contain Se in the form of selenocysteine. The fact that their formation had priority over that of glutathione peroxidase during insufficient Se intake is an indication of their biological significance. Special interest in the prostatic epithelial selenoprotein derives from a possible inverse relationship between the Se status and the incidence of prostate cancer observed in epidemiological studies, whereas with the 34 kDa-selenoprotein its appearance during the condensation phase of the spermatid nuclei might suggest its participation in some processes of sperm maturation.

Protein-bound selenium in the seeds of coco de mono (Lecythis ollaria)

High selenium concentrations (7-12 g/kg dry mass) were found in the seeds of the selenium-accumulator plant coco de mono (Lecythis ollaria). In order to obtain information on the protein-bound part of selenium in extracts of these seeds, dialysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used combined with neutron activation analysis. Extractions were carried out at pH 4.5 and 7.5. In both cases about 90% of the element was dissolved. Of the extracted selenium only 9% was shown to be firmly bound to proteins at pH 4.5 and 29% at pH 7.5. For the protein-bound selenium, concentrations of 0.7 g and 2.4 g per kg of seeds and 40 and 25 g per kg of extractable protein were determined at pH 4.5 and 7.5, respectively. By analyzing the protein fractions separated by SDS-PAGE the element was found to be present in extremely selenium-rich proteins with molecular masses below 20 kDa.

A new selenoprotein found in the glandular epithelial cells of the rat prostate

An inverse relationship between the Se status and the incidence of prostate cancer suggests a significant role of Se in this organ. After labeling of rats with 75Se and sodium dodecyl sulfate-polyacrylamide gel electrophoresis a strongly labeled prostatic 15-kDa protein band was found which was equally distributed among the different lobes. It was localized in the epithelial cells of isolated acini but did not appear in the prostatic secretion. By two-dimensional electrophoresis the band was resolved into three spots with pI-values around 4.5. The most strongly labeled spot stemmed from a cytosolic selenoprotein with an apparent native molecular mass of about 300 kDa which contained Se in the form of selenocysteine. The fact that with insufficient Se intake the element is preferentially incorporated into this compound as compared with glutathione peroxidase implies an important function of this newly found prostatic epithelial selenoprotein (PES).