Background: Weaning is an essential part of critically ill patients who are on mechanical ventilation. Weaning was classified into simple, difficult and prolonged. Some patients are easily weaned off and others require a more prolonged duration.
Methods: 52 patients admitted to the respiratory intensive care unit (RICU) and requiring mechanical ventilation were successfully weaned and classified into simple (20, 37.7%), difficult (20, 37.7%) and prolonged weaning (13, 24.5%). Factors associated with prolonged weaning and outcomes were determined.
Results: A total of 53 intubated patients admitted to the RICU (30 (56.6%) males), aged (59.8±14.3) years were included. The following factors are associated with prolonged weaning: ↓ed serum mg++(P< 0.0001) & CA++(P< 0.0001) , ↑ed BUN level (P= 0.001), ↑ed PaCO2 (P0.04), ↓ed SaO2% (P0.0001),presence of ≥2 co-morbidities (P0.02), prolonged duration of MV (P<0.0001) and long ICU stay (P<0.0001). There was no significant relation between prolonged weaning and Modes of MV (p0.2), also A-a gradient ↓ed in patients with prolonged weaning but not significant (P=0.5). In multivariate analysis, prolonged weaning was independently associated with serum Mg+ (OR 0.03, 95% CI 0.003–0.24, P <0.001), and SaO2% change (the beginning- the end of weaning trial) OR 0.91, 95%CI 0.83–0.99, P < 0.04). Regarding baseline serum Mg++ & tidal volume, the cutoff point for predicting prolonged weaning was (≤1.5 .mmol/l & ≤450 ml) with, sensitivity, specificity, PPV NPV and accuracy (61.5%, 92.5%, 72.7%, 88.1%, 77%, P ˂0.0001 and77%,55%, 36% 88%, 66%, P ˂ 0.02, respectively).The cutoff  points of PaCO2 ≥49 mmHg & SaO2% ≤91 at first weaning trial & SaO2% change ≥5 (between the beginning and the end of a weaning trial) were strongly associated with prolonged weaning (P ˂0.02, ˂ 0.0001& ˂0.003, respectively). Prolonged weaning was significantly associated with high mortality rate (P˂ 0.0001).
Conclusions: Several factors were associated with prolonged weaning, however, when subjected to multivariate analysis, only serum Mg++& SaO2% change significantly predict prolonged weaning. Prolonged weaning is associated with increased ICU stay and higher rate of tracheostomy.
Clinical Implications: Prolonged mechanical ventilation is associated with higher rate of reintubation, tracheostomy rate, longer ICU stay and higher mortality. Identification and correction of factors associated with prolonged weaning may change the outcome and prognosis of these patients. In addition, early intervention such as tracheostomy is likely to benefit these patients