Acute Kidney Injury in Mechanically Ventilated Cardiac Intensive Care Unit Patients: Clinical Characteristics, Renal Replacement Therapy, and Outcomes

Abstract

Objective: Acute kidney injury (AKI) is a frequent complication of critical cardiovascular illness and may be particularly relevant among patients requiring invasive mechanical ventilation. This study aimed to determine the frequency of registry-recorded AKI, characterize associated demographic, clinical, and biochemical features, and compare renal replacement therapy (RRT) exposure and mortality outcomes among mechanically ventilated patients admitted to a cardiac intensive care unit (CICU). Methodology: This single-center cohort study analyzed prospectively maintained clinical data from the MEGAROX_ICU database at the National Institute of Cardiovascular Diseases, Karachi, Pakistan. Consecutive adults aged ≥18 years requiring invasive mechanical ventilation for a cardiac indication between 1 April 2022 and 30 April 2025 were included. AKI status was obtained from the registry, which used a KDIGO-based classification framework. Descriptive statistics and unadjusted comparisons between patients with and without AKI were performed. Results: A total of 1,591 mechanically ventilated CICU patients were included; mean age was 58.1 ± 13.4 years, 970 (61.0%) were male, and 1,022 (64.2%) had registry-recorded AKI. Compared with patients without AKI, those with AKI were older (59.3 ± 13.0 vs. 56.1 ± 14.0 years, p<0.001), more frequently male (63.7% vs. 56.1%, p=0.003), and more frequently had diabetes (44.9% vs. 38.1%, p=0.009) and documented pre-existing chronic kidney disease (8.8% vs. 0.4%, p<0.001). Cardiogenic shock and septic shock were also more frequent in the AKI group. Any recorded RRT exposure occurred more frequently among patients with AKI than among those without AKI (16.8% vs. 3.5%, p<0.001), and ICU mortality was higher (24.5% vs. 15.8%, p<0.001). Among hospital survivors with known follow-up status, approximately 90-day mortality did not differ significantly between the AKI and non-AKI groups (9.1% vs. 6.7%, p=0.162). Among 192 patients with any recorded RRT exposure, 120 (62.5%) were discharged alive, 64 (33.3%) died in the ICU, and 8 (4.2%) died after ICU transfer. Conclusion: Registry-recorded AKI was common among mechanically ventilated CICU patients and was associated with greater RRT exposure and higher ICU mortality. Patients with AKI also differed from those without AKI across several demographic, comorbidity, hemodynamic, and biochemical characteristics.