Association of persistent acute kidney injury and renal recovery with mortality in hospitalised patients

Abstract

Objectives: Acute kidney injury (AKI) affects up to one-quarter of hospitalised patients and 60% of patients in the intensive care unit (ICU). We aim to understand the baseline characteristics of patients who will develop distinct AKI trajectories, determine the impact of persistent AKI and renal non-recovery on clinical outcomes, resource use, and assess the relative importance of AKI severity, duration and recovery on survival.

Methods: In this retrospective, longitudinal cohort study, 156 699 patients admitted to a quaternary care hospital between January 2012 and August 2019 were staged and classified (no AKI, rapidly reversed AKI, persistent AKI with and without renal recovery). Clinical outcomes, resource use and short-term and long-term survival adjusting for AKI severity were compared among AKI trajectories in all cohort and subcohorts with and without ICU admission.

Results: Fifty-eight per cent (31 500/54 212) had AKI that rapidly reversed within 48 hours; among patients with persistent AKI, two-thirds (14 122/22 712) did not have renal recovery by discharge. One-year mortality was significantly higher among patients with persistent AKI (35%, 7856/22 712) than patients with rapidly reversed AKI (15%, 4714/31 500) and no AKI (7%, 22 117/301 466). Persistent AKI without renal recovery was associated with approximately fivefold increased hazard rates compared with no AKI in all cohort and ICU and non-ICU subcohorts, independent of AKI severity.

Discussion: Among hospitalised, ICU and non-ICU patients, persistent AKI and the absence of renal recovery are associated with reduced long-term survival, independent of AKI severity.

Conclusions: It is essential to identify patients at risk of developing persistent AKI and no renal recovery to guide treatment-related decisions.

Keywords: critical care outcomes; data interpretation; informatics; statistical.

Figure 1

Hospital and long-term outcomes by trajectories of acute kidney injury (AKI) in hospitalised adult patients. (A) Trajectories of AKI in hospitalised adult patients. 1-year follow-up outcome was reported among hospital survivors. (B) Adjusted Kaplan-Meier survival curves and number at risk by AKI trajectories. Propensity score based inverse weighting was used to plot adjusted Kaplan-Meier curves where propensity of being in a trajectory group was calculated using multinomial logistic model that included patient demographics (age, gender, ethnicity), and Charlson Comorbidity Index score. (C) Hazard ratios for all-cause mortality by AKI trajectories. ^aSignificantly different from no AKI group (Bonferroni-adjusted p<0.05). ^bSignificantly different from rapidly reversed AKI group (Bonferroni-adjusted p<0.05). ^cSignificantly different from persistent AKI with renal recovery (Bonferroni-adjusted p<0.05). ^dAdjusted for age, gender, ethnicity, Charlson Comorbidity Index score, and need for mechanical ventilation for more than 2 days and need for intensive care unit admission for more than 2 days. RRT, renal replacement therapy.

Figure 2

Hospital and long-term outcomes by trajectories of acute kidney injury (AKI) in hospitalised adult patients stratified by ICU admission. (A) Trajectories of AKI in hospitalised adult patients who have been admitted to ICU during hospitalisation. 1-year follow-up outcome was reported among hospital survivors. (B) Adjusted Kaplan-Meier survival curves and number at risk by AKI trajectories injury in hospitalised adult patients who have been admitted to ICU during hospitalisation. Propensity score based inverse weighting was used to plot adjusted Kaplan-Meier curves where propensity of being in a trajectory group was calculated using multinomial logistic model that included patient demographics (age, gender, ethnicity) and Charlson Comorbidity Index score. (C) HRs for all-cause mortality by AKI trajectories in hospitalised adult patients who have been admitted to ICU during hospitalisation. (D) Trajectories of AKI in hospitalised adult patients who have not been admitted to ICU during hospitalisation. 1-year follow-up outcome was reported among hospital survivors. (E) Adjusted Kaplan-Meier survival curves and number at risk by AKI trajectories in hospitalised adult patients who have not been admitted to ICU at any time during hospitalisation. Propensity score based inverse weighting was used to plot adjusted Kaplan-Meier curves where propensity of being in a trajectory group was calculated using multinomial logistic model that included patient demographics (age, gender, ethnicity) and Charlson Comorbidity Index score. (F) Hazard ratios for all-cause mortality by AKI trajectories in hospitalised adult patients who have not been admitted to ICU at any time during hospitalisation. ^aSignificantly different from no AKI group (Bonferroni-adjusted p<0.05). ^bSignificantly different from rapidly reversed AKI group (Bonferroni-adjusted p<0.05). ^cSignificantly different from persistent AKI with renal recovery (Bonferroni-adjusted p<0.05). ^dAdjusted for age, gender, ethnicity, Charlson Comorbidity Index score, and need for mechanical ventilation for more than 2 days and need for ICU admission for more than 2 days. ^eAdjusted for age, gender, ethnicity, and Charlson Comorbidity Index score. ICU, intensive care unit; RRT, renal replacement therapy.

Figure 3

Adjusted Kaplan-Meier survival curves and number at risk by AKI subphenotypes obtained stratifying by (A) no AKI vs any AKI (B) AKI stratified by severity (C) AKI stratified by severity and duration (D) AKI stratified by severity and trajectories of AKI using duration and recovery of AKI. Propensity score based inverse weighting was used to plot adjusted Kaplan-Meier curves where propensity of being in a trajectory group was calculated using multinomial logistic model that included age, gender, ethnicity and Charlson Comorbidity Index score. Adjusted hazard ratios were obtained adjusting for the same variables as well as need for mechanical ventilation for more than 2 days and need for intensive care unit admission for more than 2 days. AKI, acute kidney injury.