Mild acute kidney injury is associated with increased mortality after cardiac surgery in patients with eGFR < 60 mL/min/1.73 m(2).

BACKGROUND

A small increase in serum creatinine after cardiac surgery has been associated with increased mortality. However, it is unclear whether this association varies with baseline renal function.

METHODS

We retrospectively reviewed data on 1359 patients who underwent cardiac surgery over a 4-year period in two tertiary care hospitals including demographic data, comorbid conditions, and intra- and postoperative complications using a standardized form. We followed patients for 90 days postoperatively and death rates and length of hospital stay were noted.

RESULTS

The incidence of acute kidney injury (AKI) after cardiac surgery was 40.2%. Patients were grouped into terciles based on change in serum creatinine. Kaplan-Meier survival analysis and Cox regression analysis showed that the development of AKI with a small increase in serum creatinine of more than 0.3 mg/dL from baseline (tercile 3) was associated with a higher risk of mortality within 90 days and 7 days longer hospitalization following a cardiac surgery. Stratified analysis showed that only patients with baseline eGFR < 60 mL/min/1.73 m (2) had fivefold higher mortality with rise of serum creatinine >0.3 mg/dL.

CONCLUSIONS

Patients with baseline eGFR < 60 mL/min/1.73 m(2) had increased risk of mortality after cardiac surgery with a small increase in serum creatinine whereas a similar increase in serum creatinine in those with eGFR ≥ 60 mL/min/1.73 m(2) did not increase mortality.