Impact of renal dysfunction on in-hospital mortality of patients with severe chronic obstructive pulmonary disease: a single-center Italian study

BACKGROUND: We conducted a study, based on discharge hospital sheets [International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM)], in order to evaluate the relationship between chronic kidney disease (CKD), acute kidney injury (AKI), multi-morbidity, and in-hospital mortality (IHM). METHODS: This study included all hospital admissions for chronic obstructive pulmonary disease (COPD) exacerbations between January 1, 2000, and December 31, 2013, recorded in the database of the University Hospital St. Anna of Ferrara. Age, sex, and diagnosis of CKD and AKI were collected, and Charlson comorbidity index (CCI) was calculated by ICD-9-CM codes. IHM was our main outcome. RESULTS: We analyzed 7073 subjects with COPD exacerbation; they were more frequently male (56.9 vs 43.1 %), and mean age was 76.7 ± 9.8 years. Diagnosis of CKD was present in 771 patients (10.9 %), while AKI was diagnosed in 354 cases (5 %). A total of 554 patients (7.8 %) died during hospitalization, and LOS was 10.3 ± 11.2 days (median 8 days); the CCI corrected for CKD was 2.30 ± 1.65. Univariate analysis showed that IHM group had higher age (81.2 ± 7.9 vs 76.3 ± 9.9 years, p < 0.001), CCI (2.61 ± 2.21 vs 2.28 ± 1.62, p = 0.001), and LOS (11.1 ± 15.1 vs 10.3 ± 10.8 days, p = 0.001) and developed AKI more frequently (16.6 vs 4 %, p < 0.001) than survivors. Multivariate logistic regression analysis showed an independent association of IHM with age (OR 1.063; 95 % CI 1.050-1.075, p < 0.001), male sex (OR 1.229; 95 % CI 1.016-1.486, p = 0.033), logCCI (OR 2.051; 95 % CI 1.419-2.964, p < 0.001), and AKI (OR 3.849; 95 % CI 2.874-5.155, p < 0.001). CONCLUSIONS: Acute kidney injury (AKI) represents a very important predictive factor of IHM in male older adult with multi-morbidity admitted because of COPD exacerbations.