Bacterial Pneumonia and Acute Kidney Injury: Association and Impact on Outcomes of Patients Hospitalized for Acute Exacerbation of Chronic Obstructive Pulmonary Disease (COPD) in the United States.

Abstract

Introduction: This study aims to investigate the association between bacterial pneumonia and acute kidney injury (AKI), which develops during hospitalizations for an acute exacerbation of chronic obstructive pulmonary disease (AECOPD), and their impact on patient outcomes.

Methods: We performed a retrospective observational study on the United States National Inpatient Sample (USNIS) from 2016 to 2022, using ICD-10 codes to identify patients admitted to hospitals with an AECOPD who developed bacterial pneumonia and/or AKI during their hospital stay. We compared the clinical outcomes, including endotracheal intubation, in-hospital length of stay, and all-cause hospital mortality among four groups of patients: AECOPD, AECOPD with bacterial pneumonia and no AKI (PAECOPD), AECOPD with AKI and no bacterial pneumonia (KAECOPD), AECOPD with both bacterial pneumonia and AKI (PKAECOPD). We investigated the microorganism distribution of bacterial pneumonia and mortality by pathogen. We also used multivariate logistic and linear regression to investigate the correlation between outcomes and variables, including age, gender, race, hospital bed size, hospital location, bacterial pneumonia, AKI, and Charlson's comorbidity index.

Results: There were 2,548,188 weighted admissions, including 2,247,833 cases of AECOPD (88.21%); 34,930 cases of PAECOPD (1.37%); 258,360 cases of KAECOPD (10.14%); and 7,065 cases of PKAECOPD (0.28%). The average age of patients who died in hospitals was 6 years older than that of survivors (73.19 vs 67.70 years, p<0.01). Patients requiring endotracheal intubation were, on average, a year younger than those who did not (66.61 vs 67.77 years, p<0.01). White patients had poorer survival than Black, Hispanic, and other races. Females had lower hospital mortality than males by odds ratio (OR) 0.91 (p=0.004). AECOPD patients with bacterial pneumonia had a higher AKI rate than those without bacterial pneumonia (16.82% vs 10.31%, p<0.01). The PKAECOPD group had the poorest outcomes compared with the other groups, including higher endotracheal intubation incidence (27.18%), longer hospital stay (12.89 days), and higher all-cause hospital mortality (13.39%). Factors leading to increased all-cause hospital mortality included endotracheal intubation (OR 32.75, p<0.01), AKI (OR 2.33, p<0.01), bacterial pneumonia (OR 1.71, p<0.01), Charlson's comorbidity index (OR 1.10, p<0.01), and older age (OR 1.05, p<0.01). Factors leading to increased hospital stay by at least a day included endotracheal intubation (6.13 days, p<0.01), bacterial pneumonia (3.03 days, p<0.01), and AKI (1.12 days, p<0.01). The most commonly identified pathogens causing bacterial pneumonia included other gram-negative bacilli (12.47%), Pseudomonas aeruginosa (11.54%), Streptococcus pneumoniae (7.22%), Methicillin-resistant Staphylococcus aureus (MRSA) (7.00%), Mycoplasma pneumoniae (4.70%), and Hemophilus influenzae (4.63%). In approximately forty percent of cases, no specific pathogen was identified. Mortality was highest for patients with "other bacteria" (23.43%), MRSA (22.86%), and Pseudomonas aeruginosa (20%).

Discussion: Patients admitted with an AECOPD had a high incidence of AKI during hospital admission, approximately 10%. Patients with an AECOPD who developed bacterial pneumonia represented a small proportion of admissions (1.65%) but had a higher risk of AKI (16.82%). These patients were likely to be infected with pathogens including Pseudomonas aeruginosa, other gram-negative bacteria, and MRSA. Patients with both AKI and bacterial pneumonia had the highest all-cause hospital mortality.

Conclusion: Our study found that hospitalized AECOPD patients with bacterial pneumonia had a higher rate of AKI than those without bacterial pneumonia, and the population of AECOPD patients with both bacterial pneumonia and AKI had markedly higher all-cause hospital mortality, longer hospital stays, and greater need for endotracheal intubation. Therefore, minimizing the association between bacterial pneumonia and AKI may help improve the prognosis of patients admitted with an AECOPD.