Predictors of successful weaning

Abstract

Background
Early release of patients from mechanical ventilation and intubation associated with significant decrease in mortality and morbidities.


Aim
Evaluation of echocardiography and oxidative stress markers in the prediction of weaning failure.


Patients and methods
In all, 120 mechanically ventilated patients were included in the study. Patients were evaluated by tissue Doppler transthoracic echocardiography before and during the spontaneous breathing trial (SBT). In addition to ventilatory parameters, blood samples were obtained for the measurement of lipid peroxidase, glutathione oxidase, and nitric oxide. Different parameters were compared between failed and successful weaning groups.


Results
During SBT, respiratory rate, heart rate, and rapid shallow breathing index (RSBI) were significantly increased compared with before SBT. The serum level of nitric oxide before SBT was significantly decreased in the failed group. All cardiac dimensions significantly increased during SBT compared with before SBT; moreover, the left ventricular dimensions increased significantly in the failed group during SBT. There was significant decrease in right ventricular systolic function during SBT as estimated by tricuspid annular plane systolic excursion (TAPSE) and myocardial performance index. Weaning success was positively correlated with tidal volume, TAPSE, and nitric oxide, while negatively correlated with lipid peroxidase, respiratory rate, left ventricular end-diastolic dimension, and E/E’ of lateral mitral valve annulus. Tidal volume more than or equal to 493 ml before SBT had the highest sensitivity for predicting successful weaning; on the other hand, during SBT left ventricular end-diastolic dimension less than or equal to 5.05 cm had 100% sensitivity and TAPSE more than or equal to 1.65 had 88.9% sensitivity. Respiratory rate less than or equal to 27.5 during SBT had the highest specificity (72.7%).


Conclusion
In comparison to oxidative stress markers, clinical assessment and bedside transthoracic echocardiography have higher sensitivity, so they can be considered valuable and cheap predictors of successful weaning.