Preoperative proteinuria is associated with long-term progression to chronic dialysis and mortality after coronary artery bypass grafting surgery

Abstract

Aims: Preoperative proteinuria is associated with post-operative acute kidney injury (AKI), but whether it is also associated with increased long-term mortality and end-stage renal disease (ESRD) is unknown.

Methods and results: We studied 925 consecutive patients undergoing CABG. Demographic and clinical data were collected prospectively, and patients were followed for a median of 4.71 years after surgery. Proteinuria, according to dipstick tests, was defined as mild (trace to 1+) or heavy (2+ to 4+) according to the results of the dipstick test. A total of 276 (29.8%) patients had mild proteinuria before surgery and 119 (12.9%) patients had heavy proteinuria. During the follow-up, the Cox proportional hazards model demonstrated that heavy proteinuria (hazard ratio [HR], 27.17) was an independent predictor of long-term ESRD. There was a progressive increased risk for mild proteinuria ([HR], 1.88) and heavy proteinuria ([HR], 2.28) to predict all-cause mortality compared to no proteinuria. Mild ([HR], 2.57) and heavy proteinuria ([HR], 2.70) exhibited a stepwise increased ratio compared to patients without proteinuria for long-term composite catastrophic outcomes (mortality and ESRD), which were independent of the baseline GFR and postoperative acute kidney injury (AKI).

Conclusion: Our study demonstrated that proteinuria is a powerful independent risk factor of long-term all-cause mortality and ESRD after CABG in addition to preoperative GFR and postoperative AKI. Our study demonstrated that proteinuria should be integrated into clinical risk prediction models for long-term outcomes after CABG. These results provide a high priority for future renal protective strategies and methods for post-operative CABG patients.

Figure 1. Proportion of freedom from long- term dialysis dependence, stratified by different severities of proteinuria defined by preoperative dipstick.

(Mild proteinuria, p = 0.166; Heavy proteinuria, p = 0.001; No proteinuria was the reference calculated by multivariable Cox proportional hazard analyses).

Figure 2. Adjusted risk for long- term all- cause mortality after hospital discharge stratified by different severities of proteinuria defined by preoperative dipstick.

(Mild porteinuria, p = 0.005; Heavy proteinuria, p = 0.008; no proteinuria was the reference calculated by multivariable Cox proportional hazard analyses).

Figure 3. Proportion of freedom from long- term composite outcome after hospital discharge, composite outcome of ESRD and mortality, stratified by different severities of proteinuria defined by preoperative dipstick.

(Mild proteinuria, p<0.001; Heavy proteinuria, p<0.001; No proteinuria was the reference calculated by multivariable Cox proportional hazard analyses).

Figure 4. The composite outcome after hospital discharge (long- term end-stage renal disease or mortality) for urinary proteinuric categories across chronic kidney disease (CKD) categories using Cox proportional hazards regression (a) plot of freedom from composite outcome, ^* p<0.05; ^** p<0.01; and ^*** p<0.001 compared to patients with preserved eGFR and normal proteinuria.

(b) Hazard ratio (HRs) stratified by proteinuria, baseline kidney function, and postoperative acute kidney injury (AKI) adjusted for factors listed in Table 1. The horizontal bars represent 95% CIs for HRs of participants who had proteinuria for various values of CKD stages and AKI.