The impact of mild renal dysfunction on isolated cardiopulmonary coronary artery bypass grafting: a retrospective propensity score matching analysis

Mild preoperative renal dysfunction (RD) is not rare in patients receiving isolated cardiopulmonary coronary artery bypass grafting (CCABG). However, there are not too many studies about the impact of mild preoperative RD on in-hospital and follow-up outcomes after isolated CCABG. This single-centre, retrospective propensity score matching study designed to study the impact of mild preoperative RD on in-hospital and long-term outcomes after first isolated CCABG.

After propensity score matching, 1144 patients with preoperative estimated glomerular filtration rate (eGFR) of more than 60 ml/min/1.73 m² receiving first isolated CCABG surgery from January 2012 to December 2015 entered the study, who were divided into 2 groups: A group (eGFR ≥90 ml/min/1.73 m2, n = 572) and B group (eGFR of 60–89 ml/min/1.73 m2, n = 572). The in-hospital and long-term outcomes were recorded and analyzed. The mean follow-up time was 54.4 ± 10.7 months. Acute kidney injury (AKI) was defined and classified according to the Acute Kidney Injury Network (AKIN) criteria.

The 2 propensity score-matched groups had similar baseline and procedure except the baseline eGFR. There were 8 patients died in A group (mortality is 1.4%) and 14 died in B group (mortality is 2.5%) during the in hospital and 30-day postoperatively(χ² = 1.159, p = 0.282). There were totally 38 patients lost to follow-up, 18 in group A and 20 in group B. 21 patients died in group A and 37 died in group B during the follow-up, and long-term survival in group A was higher than in group B (96.2% vs 93.1%, χ² = 4.336, p = 0.037). Comparing with group A, group B was associated with an increased rates and severity of AKI postoperatively (total AKI: 62 vs 144. AKIN stageI: 54 vs 113; AKIN stageII: 6 vs 22; AKIN stageIII: 2 vs 9, p<0.0001). During follow-up, group B also had a higher rate of new onset of dialysis (0 vs 6, χ² = 4.432, p = 0.039). Multivariable logistic regression showed that comparing with A group, the HR for long-term mortality and new onset of dialysis in B group was 1.67 and 1.52 respectively (95%CI 1.09–2.90, p = 0.035; 95%CI 1.14–2.49, p = 0.027).

Comparing with normal preoperative renal function, patients with mild preoperative RD had a similar in-hosptial mortality, but with an increased in-hosptial rates and severity of AKI, and with a decreased long-term survival and increased long-term new onset of dialysis.