Risk factors and clinical significance of acute kidney injury after on-pump or off-pump coronary artery bypass grafting: a propensity score-matched study

OBJECTIVES: Our goal was to investigate risk factors for acute kidney injury (AKI) after coronary artery bypass grafting (CABG) and the impact of AKI on short-term outcomes. METHODS: Data on 1395 patients (1261 who had isolated CABG and 134 with other operations) who underwent non-emergent CABG from January 2013 to March 2016 were retrospectively collected from a single centre. Logistic regression was performed to analyse risk factors. Cox regression was used to analyse the impact of AKI on the postoperative 30-day death rate. A 1:1 propensity score matching was performed to balance the baseline characteristics. RESULTS: The incidence of AKI with on-pump and off-pump coronary artery bypass was 10.4% and 3.5%, respectively. With logistic regression, duration of surgery was a risk factor for AKI (stage ≥2); previous hypertension, preoperative renal function insufficiency and the presence of cardiopulmonary bypass (CPB) were risk factors for mild AKI (stage ≥1). CPB time >207.5 min could be used to predict AKI (sensitivity 79.2%, specificity 78.6%) in the combined group. After adjusting for the duration of the operation, postoperative AKI (stage ≥1) was a risk factor for 30-day death and there was no difference in the 30-day death rate between on-pump and off-pump CABG. CONCLUSIONS: The use of CPB was a risk factor for mild AKI that did not affect the 30-day death rate of CABG whereas moderate to severe AKI caused by prolonged CPB time associated with surgical complexity affected the 30-day death rate. AKI may indicate surgical injury. The decision to use the on- or off-pump technique does not affect the 30-day death rate of CABG.