Proposed definitions of weaning success (i.e., patients discharged alive without needing breathing assistance) for these difficult-to-wean patients have included 48 h, 7 days or 14 days without need of MV, or liberation from ventilator support at the time of hospital discharge[8–10,13] or at 6 months–1 year after the onset of MV. Between 30 and 53% of chronically critically ill patients are liberated from MV in the acute care hospital. Average time to ventilator liberation varies with the severity and type of illness or injury, but typically ranges from 16 to 37 days after intubation for respiratory failure. If the patient fails to wean from ventilator dependence within 60 days, they will probably not do so later. Better outcomes are reported for some specialized WCs, but they often select patients with a higher potential for ventilator liberation and rehabilitation.[13,54,55] The literature reports great variability in the clinical outcomes of WCs.[8,13,56] Observational studies indicate a 34–60% successful weaning rate in WCs.[57,58] Recently it has been shown that the sequential activity of a RICU and a WC resulted in an additive weaning success rate (up to 80%) of difficult-to-wean patients with reduced costs compared with the ICU. Such differences in weaning success definition may be related to differences in patient population, discharge criteria and specific characteristics of the institutions. Similarly, hospital mortality and LOS are widely variable.
Hospital mortality varies from 6 to 50%, depending on admission criteria, severity of clinical status and underlying diseases, and likelihood of transfer to a different facility when patients become acutely ill.[9–12,24] While patients who remain ventilator dependent are at a higher risk of death, successful weaning does not assure long-term survival as most patients have underlying comorbid conditions, residual organ dysfunction and intercurrent complications. Acute hospital mortality for unselected patients is generally reported in the range of 20–49%.[23,52,53] Across study populations, 1-year mortality is 48–68%, with little change over the past 20 years.[31,52,54] Compared with patients requiring short-term MV, the risk of death in patients with prolonged MV remains particularly high between 60 and 100 days after MV initiation.[60,61] However, comparison among studies of different centers and different periods may be not appropriate, as weaning success seems to strongly depend on patients' complexity and comorbidities, hospital organization and personnel expertise,[62,63] availability of early physiotherapy,[43–45] use of weaning protocols, patients' autonomy and families' preparation for home discharge with MV. When evaluating outcomes, it is necessary to consider the severity of patients at admission, as Schonhofer et al. showed that use of the Acute Physiological And Chronic Health Evaluation II prognostic system at admission was able to successfully differentiate from unsuccessfully weaned patients.
Studies have identified chronically critically ill patients by elective placement of a tracheostomy to facilitate prolonged MV and weaning efforts.[66–68] The need of elective tracheostomy means that the patient will neither wean nor die in the immediate future, a point of demarcation between acute and chronic critical illness that is considered both clinically meaningful and practical. The use of tracheostomy seems to increase in patients requiring prolonged MV, although the advantage of this strategy on outcome is still discussed. In some studies, tracheostomy did not favorably influence ICU survival,[70,71] whereas it has been reported that tracheostomy performed in ICU for long-term MV patients was associated with lower ICU and in-hospital mortality rates. There is considerable variability in the indications and time considered optimal for performing tracheostomy. Among mechanically ventilated adult ICU patients, early tracheotomy compared with late tracheostomy did not result in a statistically significant improvement in the incidence of ventilator-associated pneumonia. Nevertheless, some authors support the usefulness of tracheostomy protocols based on a standardized approach to ventilator weaning. Consequently, the decision to perform tracheostomy is more of an experience- than an evidence-based decision and should be made with caution. Efforts should be made to identify patients who might clearly benefit from this technique to avoid unnecessary and unwanted prolonged MV.
Tracheostomy tube malposition is a relatively common complication in patients with ARF who are recovering from critical illness and is associated with need for prolonged MV; therefore, it should be considered in mechanically ventilated patients who unexpectedly fail to be liberated from MV. Although surgical expertise is a risk factor, identifying patients who are at risk for this complication is difficult. A recent survey on 719 patients from 22 Italian RICUs shows that tracheostomy was maintained in a substantial proportion of patients without any need for home MV. The clinical relevance of decannulation at discharge is supported by a recent study that showed that a lack of decannulation of conscious tracheostomized patients before ICU discharge to the general ward was associated with higher mortality.
The reported outcome of prolonged weaning may be not satisfactory for patients and relatives. In a study of 1-year patient outcomes for prolonged MV, patients were significantly worse than expected by patients' relatives and physicians. Lack of prognostication about outcomes, discordance between relatives and physicians about potential outcomes and relatives' unreasonably optimistic expectations seem to be potentially modifiable deficiencies in relative–physician interactions. Recently, we studied the families' perception of care in patients under home MV during the last 3 months of life. In 11 respiratory units, we submitted a 35-item questionnaire to relatives of 168 deceased patients exploring six domains: symptoms, awareness of disease, family burden, dying, and medical and technical problems. The response rate was 98.8%. The majority of patients complained of respiratory symptoms and were aware of the severity and prognosis of the disease. Family burden was high, especially in relation to money need. During hospitalization, 74.4% of patients were admitted to the ICU. A total of 78 patients died at home, 70 patients in a medical ward and 20 in the ICU. Overall, 27% of patients received resuscitation maneuvers. Hospitalizations and family economic burden were unrelated to diagnosis and MV. Families of the patients did not report major technical problems with the use of ventilators. In comparison with mechanically invasively ventilated patients, noninvasively ventilated patients were more aware of prognosis, used more respiratory drugs, changed ventilation time more frequently and died less frequently when under MV.
Expert Rev Resp Med. 2010;4(5):685-692. © 2010 Expert Reviews Ltd.
Cite this: The Difficult-to-wean Patient - Medscape - Oct 01, 2010.