PURPOSE: Acute Kidney Injury (AKI) has an incidence of 20-50 % in patients admitted in Intensive Care Unit. As weaning failure is associated with increased morbidity, its prediction and understanding of its physiological basis holds extreme importance in guided management and prognostication of these patients. We conducted this prospective, observational, single - center study to evaluate the efficacy of transthoracic echocardiography (TTE) and lung ultrasonography (LUS) in predicting weaning failure in patients with AKI requiring mechanical ventilation. METHODS: We performed LUS and TTE before and 2 h after initiating spontaneous breathing trials (SBT) in 32 mechanically ventilated critically ill patients with AKI. Extubation was decided by an independent physician. LUS included global and anterior LUS scores. TTE included measurement of E/A and E/e' ratios to determine LV filling pressures. RESULTS: Out of 32 patients included in this study, weaning failure was observed in 17 (n = 17, 53 %) patients (weaning success n = 15, 47%). Demographic and baseline laboratory parameters were comparable between the study groups. Fluid balance [+370 (250-530)] and SOFA score [8 (7-9)] on admission were significantly higher in weaning failure group (p <
0.001, p = 0.049). LUS scores and difference between LUS scores before and at the end of the SBT were significantly higher among the weaning failure group. The model consisting of baseline variables, SOFA score on the day of weaning and SBT induced changes in global lung score showed highest ability to predict weaning failure with AUC of 0.965, R CONCLUSION: In mechanically ventilated critically ill patients with AKI, LUS scores can predict weaning failure after SBT. CTRI NUMBER: CTRI/2020/12/029565.