Predictors of long-term prognosis in acute kidney injury survivors who require continuous renal replacement therapy after cardiovascular surgery

Abstract

The long-term prognosis of patients with postoperative acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT) after cardiovascular surgery is unclear. We aimed to investigate long-term renal outcomes and survival in these patients to determine the risk factors for negative outcomes. Long-term prognosis was examined in 144 hospital survivors. All patients were independent and on renal replacement therapy at hospital discharge. The median age at operation was 72.0 years, and the median pre-operative estimated glomerular filtration rate (eGFR) was 39.5 mL/min/1.73 m2. The median follow-up duration was 1075 days. The endpoints were death, chronic maintenance dialysis dependence, and a composite of death and chronic dialysis. Predictors for death and dialysis were evaluated using Fine and Gray's competing risk analysis. The cumulative incidence of death was 34.9%, and the chronic dialysis rate was 13.3% during the observation period. In the multivariate proportional hazards analysis, eGFR <30 mL/min/1.73 m2 at discharge was associated with the composite endpoint of death and dialysis [hazard ratio (HR), 2.1; 95% confidence interval (CI), 1.1-3.8; P = 0.02]. Hypertension (HR 8.7, 95% CI, 2.2-35.4; P = 0.002) and eGFR <30 mL/min/1.73 m2 at discharge (HR 26.4, 95% CI, 2.6-267.1; P = 0.006) were associated with dialysis. Advanced age (≥75 years) was predictive of death. Patients with severe CRRT-requiring AKI after cardiovascular surgery have increased risks of chronic dialysis and death. Patients with eGFR <30 mL/min/1.73 m2 at discharge should be monitored especially carefully by nephrologists due to the risk of chronic dialysis and death.

Fig 1. Cumulative incidences of the composite of death and initiation of chronic dialysis.

(1) Indicates the cumulative incidence of initiation of chronic dialysis (13.3%) and (2) indicates the cumulative incidence of death (34.9%) during the observation period. The cumulative incidence of the composite endpoint of death and initiation of chronic dialysis was 48.2%.

Fig 2. Kaplan-Meier survival curves depicting the period between discharge and the composite endpoint of death and chronic dialysis initiation.

Association between estimated glomerular filtration rate (eGFR) ≥ or <30 mL/min/1.73 m² at hospital discharge and composite endpoint.

Fig 3. Cumulative incidences curves depicting period of time between discharge and chronic dialysis initiation censored for death.

Association between estimated glomerular filtration rate (eGFR) ≥30 or <30 mL/min/1.73 m² at hospital discharge and chronic dialysis initiation.

Fig 4. Cumulative incidence curves for death before initiation of chronic dialysis.

Association between age ≥ or <75 years and death.