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How can we describe the weaning process that takes place in Intensive Care Units around the world?

What to expect? What are the risk factors for worse prognosis? What percentage of patients were we successfully weaned off? What can delay the start of the weaning process?

✍ Trying to answer this question, the WEAN SAFE study emerged: a large observational, multicenter, prospective cohort study, carried out in 481 Intensive Care Units (ICU) in 50 countries(1). It was published in January/2023, in Lancet Respiratory Medicine.

👉 To access the study, click here.

From October/2017 to June/2018, 10232 patients were evaluated for eligibility and 4363 were excluded, the vast majority for not reaching 48 hours of Mechanical Ventilation (MV). 5869 participants took part in the study.

📝 The population studied was adult patients (over 16 years old) admitted to the ICU with at least 48 hours on MV. From then on, the weaning process, in particular, was closely monitored in order to assess various outcomes.

Important definitions:

In this study, some definitions are fundamental for the correct interpretation of the results. See below:

1. Eligibility criteria for weaning (modified from Boles et al)(2):

   1. Inspired oxygen fraction (FiO2) less than 50%;

   2. Positive pressure at the end of expiration (PEEP) less than 10;

   3. Use of no or low dose of vasopressors;

   4. Not be under paralyzing agent.

2. Definition of when the patient entered the weaning phase: when the first attempt to disconnect from the ventilator was performed. In intubated patients, separation was defined as an ERT or a direct extubation. In tracheostomized patients, separation was defined as a short period of T-tube testing, low respiratory support, short period of oxygenation in a tracheostomy mask, or an ERT.

3. The delay in attempting weaning from the ventilator was defined as a time interval greater than 1 day between meeting the eligibility criteria for weaning and the first attempt at weaning.

4. Weaning success was defined as: extubation without death or reintubation for 7 consecutive days or ICU discharge without invasive MV - in intubated patients; spontaneous ventilation through tracheostomy without MV for 7 consecutive days or discharge from the ICU with unassisted breathing - in tracheostomized patients.

5. Modified WIND classification:

   1. No Separation Attempt: Never subjected to ventilator separation attempt, i.e. died or transferred to another unit.

   2. Short wean: successfully weaned within 1 day after the first separation attempt.

   3. Intermediate wean: successfully weaned in more than 1 day and before 7 days after the first separation attempt.

   4. Prolonged wean: successfully wean at least 7 days after the first attempt at separation up to the 90-day follow-up limit.

   5. Failed wean: patients who underwent attempted ventilator separation but remained in need of invasive ventilatory support until day 90 or until transfer to another unit or death (unsuccessful weaning).

⚠️ An important caveat: the eligibility criteria for weaning differ from those of the main sources adopted as a reference to classify the patient as potentially suitable for the spontaneous breathing test (SBT), including the same adopted as a reference in the study (2). Usually the FiO2 used in practice to assess the eligibility of the patient's spontaneous breathing test is 40% or less and the PEEP is 8 or less or 5 or less.

✅ Results and key points:

• 65% of patients were successfully weaned.

• 77% of patients underwent at least one ventilator separation attempt.

• Among the patients submitted to at least 1 attempt to disconnect from the ventilator: 65% had a short weaning; 10%, intermediate weaning; 10%, prolonged weaning; and 15% had weaning failure. Of the latter, almost 80% died in the ICU.

• Important association between deep sedation and weaning delay and failure.

• Patient mortality was high. 32% in the ICU and 38% in the hospital, reaching a considerable number of patients with successful weaning and patients who were discharged from the ICU.

• There are important variations in weaning practices around the world; more than 30% of weaned patients were not formally submitted to an ERT.

The image below summarizes some of the findings in the study:

✍ We consider this article to be very important because: a) It was able to assess well the epidemiology of the weaning process in 50 countries; b) It offers us an epidemiological and prognostic mapping for our own practice regarding patients on MV for more than 48 hours in the most varied conditions.

⚠️ As it generates a lot of information, this is a paper that deserves to be read and interpreted carefully and also with caution in relation to possible biases. That's why we're going to make a new post in a few days about the Wean Safe study, deepening the critical analysis of the study.

🤓 How about you, Xlunger? What do you think of these results? How does this impact your practice?

Note: The article was kindly provided by Dr John Laffey, one of the main authors, at the request of our team by email. Here is our thanks.

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