Risk Factors of AKI in Acute Respiratory Distress Syndrome: A Time-Dependent Competing Risk Analysis on Severe COVID-19 Patients

Introduction: Acute kidney injury (AKI) is frequently observed in patients with COVID-19 admitted to intensive care units (ICUs). Observational studies suggest that cardiovascular comorbidities and mechanical ventilation (MV) are the most important risk factors for AKI. However, no studies have investigated the renal impact of longitudinal covariates such as drug treatments, biological variations, and/or MV parameters. Methods: We performed a monocentric, prospective, longitudinal analysis to identify the dynamic risk factors for AKI in ICU patients with severe COVID-19. Results: Seventy-seven patients were included in our study (median age: 63 [interquartile range, IQR: 53-73] years; 58 (75%) men). Acute kidney injury was detected in 28 (36.3%) patients and occurred at a median time of 3 [IQR: 2-6] days after ICU admission. Multivariate Cox cause-specific time-dependent analysis identified a history of hypertension (cause-specific hazard (CSH) = 2.46 [95% confidence interval, CI: 1.04-5.84]; P = .04), a high hemodynamic Sequential Organ Failure Assessment score (CSH = 1.63 [95% CI: 1.23-2.16]; P < .001), and elevated Paco2 (CSH = 1.2 [95%CI: 1.04-1.39] per 5 mm Hg increase in Pco2; P = .02) as independent risk factors for AKI. Concerning the MV parameters, positive end-expiratory pressure (CSH = 1.11 [95% CI: 1.01-1.23] per 1 cm H2O increase; P = .04) and the use of neuromuscular blockade (CSH = 2.96 [95% CI: 1.22-7.18]; P = .02) were associated with renal outcome only in univariate analysis but not after adjustment. Conclusion: Acute kidney injury is frequent in patients with severe COVID-19 and is associated with a history of hypertension, the presence of hemodynamic failure, and increased Pco2. Further studies are necessary to evaluate the impact of hypercapnia on increasing the effects of ischemia, particularly in the most at-risk vascular situations.