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.

Abstract 114: Does Size Matter? Comparing Cardiac Arrest Survival to Discharge Rates Based on Number of Hospital Beds

Background and Objectives: In-hospital cardiac arrest can be challenging. The frequency of events outside of critical care units is typically low which makes it a stressful event for staff. According to the HEROIC study, there were 209,000 in-hospital cardiac arrests in the United States in 2016. Only 24.9% survived. Get With the Guidelines-Resuscitation is a quality improvement tool for hospitals to measure and evaluate their in-house codes and resuscitation rates. It may be assumed that survival rates are better at larger hospitals. The objective of this study was to examine the association between in-hospital cardiac arrest rates based on the bed size of a hospital.

Methods: By using number of beds as a comparison and data from Get With the Guidelines-Resuscitation we sampled 46 hospitals in the eleven-state AHA Midwest Affiliate, (IL, IN, IA, KS, MI, MN, MO, NE, ND, SD, WI), comparing survival to discharge from cardiac arrest, with and without shockable rhythms from January 1, 2013-December 31, 2016. All patients are included in a risk adjusted formula that resides within Get With the Guidelines-Resuscitation.

Results: In our comparison, we included hospitals with licensed and/or staffed beds of <100, 100-199, 200-299, 300-399 and 400 or more beds. Our data showed that higher sustained return of spontaneous circulation rates with survival to discharge are not dictated by the size of a hospital. In fact, in all 4 years shown, successful resuscitation rates were higher at hospitals with fewer beds verses larger facilities.

Conclusions: Survival to discharge from in-hospital cardiac arrest is not dependent on hospital bed size. It is important that hospitals collect and analyze data regarding in-hospital cardiac arrests to improve survival rates beyond the 24.9% identified in the HEROIC study. A further examination looking at discharge destinations with CPC scores should be considered for a future study.

The Accuracy of Portable Monitoring in Diagnosing Significant Sleep Disordered Breathing in Hospitalized Patients

BACKGROUND

Polysomnograms are not always feasible when sleep disordered breathing (SDB) is suspected in hospitalized patients. Portable monitoring is a practical alternative; however, it has not been recommended in patients with comorbidities.

OBJECTIVE

We evaluated the accuracy of portable monitoring in hospitalized patients suspected of having SDB.

DESIGN

Prospective observational study.

SETTING

Large, public, urban, teaching hospital in the United States.

PARTICIPANTS

Hospitalized patients suspected of having SDB.

METHODS

Patients underwent portable monitoring combined with actigraphy during the hospitalization and then polysomnography after discharge. We determined the accuracy of portable monitoring in predicting moderate to severe SDB and the agreement between the apnea hypopnea index measured by portable monitor (AHIPM) and by polysomnogram (AHIPSG).

RESULTS

Seventy-one symptomatic patients completed both tests. The median time between the two tests was 97 days (IQR 25-75: 24-109). Forty-five percent were hospitalized for cardiovascular disease. Mean age was 52±10 years, 41% were women, and the majority had symptoms of SDB. Based on AHIPSG, SDB was moderate in 9 patients and severe in 39. The area under the receiver operator characteristics curve for AHIPM was 0.8, and increased to 0.86 in patients without central sleep apnea; it was 0.88 in the 31 patients with hypercapnia. For predicting moderate to severe SDB, an AHIPM of 14 had a sensitivity of 90%, and an AHIPM of 36 had a specificity of 87%. The mean±SD difference between AHIPM and AHIPSG was 2±29 event/hr.

CONCLUSION

In hospitalized, symptomatic patients, portable monitoring is reasonably accurate in detecting moderate to severe SDB.

Ultrasound-Assessed Gastric Antral Area Correlates With Aspirated Tube Feed Volume in Enterally Fed Critically Ill Patients

BACKGROUND

Enteral tube feed (ETF) intolerance occurs frequently in hospitalized patients and more so in critically ill patients. Most critical care nurses continue to assess gastric residual volume (GRV), especially among those with a history of ETF intolerance. We hypothesized that ultrasound assessment of GRV correlates directly with aspirated tube feed volume.

METHODS

This was a prospective cohort study of a convenience sample of critically ill mechanically ventilated patients admitted to an intensive care unit receiving ETF. The gastric antrum was imaged using the aorta and inferior vena cava (IVC) as landmarks concurrently and simultaneously using a curvilinear probe in the midline. All ultrasound measurements were performed at 30 degrees head up, in the supine position, and prior to the assessment of GRV by nursing staff blinding the ultrasonographer to gastric volume aspirated. Gastric antral area was determined by assessing anteroposterior (AP) and craniocaudal (CC) diameters of the gastric antrum.

RESULTS

Gastric cross-sectional area (CSA) using IVC as a landmark ( R² = 0.92, P < .0001) and aorta as a landmark ( R² = 0.86, P < .0001) correlated with aspirated volume. CC diameter of the stomach measured using the aorta as a landmark correlated with aspirated volume and increased linearly with increasing GRV ( R² = 0.78, P < .0001). A CC diameter of <10 cm using the aorta as a landmark predicted a gastric volume of <500 mL.

CONCLUSIONS

Ultrasound assessment provides accurate assessment of gastric volume in real-life settings, and the CC diameter of the gastric antrum provides a simple surrogate of GRV.

The age-associated increase in autoreactive immunoglobulins reflects a quantitative increase in specificities detectable at lower concentrations in young mice

Serum immunoglobulins reactive with several autoantigens have been reported to increase with age. The authors have studied the reactivity of serum immunoglobulins from mice between 2 and 24 months of age with antigens present in lysates of syngeneic tissue extracts from young mice. The profile of immunoglobulin binding with the immunoblots of spleen and brain tissue increased progressively with age, showing only minor differences from mouse to mouse and, with one exception, revealing that the age-associated increase in binding of immunoglobulins occurred with antigens with the same migratory position in the immunoblots detectable, at lower concentration, in sera from young mice. Not all sera from older mice had increased immunoglobulin binding when tested with extracts of skin, muscle and liver but those that did expressed increased binding with antigens in all three lysates and with the same profile shown by sera from young mice. These results are consistent with the hypothesis that the age-associated increase in autoreactive immunoglobulins represents a selective increase in autoreactive specificities expressed by serum immunoglobulins from young animals at lower levels.

Evidence for selective pressure in the appearance of monoclonal immunoglobulins during aging: studies in M54 mu-transgenic mice

Serum monoclonal immunoglobulins (M-Ig) appear during aging but little is known about the immunological factors which lead to their development. We have investigated whether such M-Ig occur as a clonally random process or result from V-region-directed selective pressures. We have analyzed a mu-transgenic mouse strain in which over 95% of all splenic B cells express the transgenic mu chain. All endogenous repertoire and mu-chain diversity are generated from the 5% of the B cells which express endogenous mu chains. Not one of the M-Ig detected in these mice were of transgene origin alone; 11 of the 14 M-Ig did not express a mu chain and none of the mu chain containing M-Ig expressed the transgene allotype alone. This observation suggests that the B cells giving rise to M-Ig are heavily selected from among the small number of B cells which express endogenous Ig. The selective factors that might act on the endogenous B cell pools are discussed.