Original Investigation
Nephrology
May 13, 2024
Blood Pressure, Readmission, and Mortality Among Patients Hospitalized With Acute Kidney Injury
Benjamin R. Griffin, Mary Vaughan-Sarrazin, Qianyi Shi, et al
JAMA Netw Open. 2024;7(5):e2410824.
doi:10.1001/jamanetworkopen.2024.10824
Question Following an episode of acute kidney injury (AKI), what is the ideal blood pressure range, and how soon after hospital discharge do potential benefits of lower blood pressure outweigh risks of mortality and readmission?
Findings In this cohort study of 80 960 patients from the Veterans Healthcare Association who had AKI during a hospital admission, systolic blood pressure of 130 to 139 mm Hg had the most favorable postdischarge risk level for mortality and readmission over time. There was a clear, time-dependent mediation of the associations of blood pressure with mortality and readmission, with patients with higher blood pressures generally being at lower risk for mortality and readmission initially, but at higher risk later in the postdischarge course.
Meaning Among patients post-AKI, there were significant, time-dependent mediations on the associations of blood pressure with mortality and readmission, which may inform the ideal degree and timing of post-AKI blood pressure treatment.
Abstract
Importance Acute kidney injury (AKI) complicates 20% to 25% of hospital admissions and is associated with long-term mortality, especially from cardiovascular disease. Lower systolic blood pressure (SBP) following AKI may be associated with lower mortality, but potentially at the cost of higher short-term complications.
Objective To determine associations of SBP with mortality and hospital readmissions following AKI, and to determine whether time from discharge affects these associations.
Design, Setting, and Participants This retrospective cohort study of adults with AKI during a hospitalization in Veteran Healthcare Association (VHA) hospitals was conducted between January 2013 and December 2018. Patients with 1 year or less of data within the VA system prior to admission, severe or end-stage liver disease, stage 4 or 5 chronic kidney disease, end-stage kidney disease, metastatic cancer, and no blood pressure values within 30 days of discharge were excluded. Data analysis was conducted from May 2022 to February 2024.
Exposure SBP was treated as time-dependent (categorized as <120 mm Hg, 120-129 mm Hg, 130-139 mm Hg, 140-149 mm Hg, 150-159 mm Hg, and ≥160 mm Hg [comparator]). Time spent in each SBP category was accumulated over time and represented in 30-day increments.
Main Outcomes and Measures Primary outcomes were time to mortality and time to all-cause hospital readmission. Cox proportional hazards regression was adjusted for demographics, comorbidities, and laboratory values. To evaluate associations over time, hazard ratios (HRs) were calculated at 60 days, 90 days, 120 days, 180 days, 270 days, and 365 days from discharge.
Results Of 237 409 admissions with AKI, 80 960 (57 242 aged 65 years or older [70.7%]; 77 965 male [96.3%] and 2995 female [3.7%]) were included. The cohort had high rates of diabetes (16 060 patients [20.0%]), congestive heart failure (22 516 patients [28.1%]), and chronic lung disease (27 682 patients [34.2%]), and 1-year mortality was 15.9% (12 876 patients). Overall, patients with SBP between 130 and 139 mm Hg had the most favorable risk level for mortality and readmission. There were clear, time-dependent mediations on associations in all groups. Compared with patients with SBP of 160 mm Hg or greater, the risk of mortality for patients with SBP between 130 and 139 mm Hg decreased between 60 days (adjusted HR, 1.20; 99% CI, 1.00-1.44) and 365 days (adjusted HR, 0.58; 99% CI, 0.45-0.76). SBP less than 120 mm Hg was associated with increased risk of mortality at all time points.
Conclusions and Relevance In this retrospective cohort study of post-AKI patients, there were important time-dependent mediations of the association of blood pressure with mortality and readmission. These findings may inform timing of post-AKI blood pressure treatment.
