Kidney and lung crosstalk during critical illness: large-scale cohort study

Background: The relationship between the lung and kidney investigated in animal and clinical models has demonstrated substantial crosstalk. We aimed to evaluate the association between single vs. concurrent AKI and ARDS and its impact on patient outcomes. Secondly, we aimed to assess whether the order of appearance of these pathologies affected patient outcomes in patients with both diseases. Methods: This single-center retrospective cohort study included adult patients admitted to the ICU from January 1, 2007 through May 1, 2018 (n = 76,988). Baseline characteristics and outcomes were compared among patients without ARDS or AKI and those with one or both ARDS and AKI. We also assessed outcomes across the order of appearance of these diseases among patients with both AKI and ARDS. Results: We enrolled 76,988 unique patients in the final analysis: 47,043 patients with neither AKI nor ARDS, 491 patients with ARDS alone, 27,928 patients with AKI alone, and 1,526 patients with both ARDS and AKI. Patients with both ARDS and AKI had higher ICU (21.2%) and hospital (28.4%) mortality compared to patients with ARDS alone (9.0% ICU mortality, 14.0% hospital mortality) or AKI alone (4.4% ICU mortality, 8.4% hospital mortality) (p < 0.001). These findings remained unchanged after adjusting for illness severity and comorbidities. Of the 1136 patients with both AKI and ARDS, 136 (12%) developed AKI first, 303 (27%) ARDS first, and 697 (61%) had simultaneous diseases. Patients who developed ARDS after AKI had significantly increased ICU (29.4%) and hospital (36.8%) mortality compared to patients who developed AKI after ARDS (13.9% ICU mortality, 21.5% hospital mortality) (p < 0.001). Conclusions: The combination of AKI and ARDS leads to worse outcomes, including longer hospital and ICU lengths of stay, higher mortality, longer kidney replacement therapy, and longer ventilation requirements than in patients with AKI or ARDS alone. Among patients with both diagnoses, those who developed ARDS after AKI had the highest mortality. Graphical abstract: [Figure not available: see fulltext.]