Perioperative acute kidney injury : risk factors and outcomes

Abstract

Background: Acute kidney injury (AKI) is defined as a sudden decrease in renal filtration function. It is common among critically ill patients and patients undergoing major surgery, especially cardiac surgery. AKI is defined by either an elevated serum creatinine (SCr) concentration or a decrease in urine production. Because AKI often presents secondary to many other critical diseases and conditions, it has historically received little attention. During the last decade, however, AKI has received greater attention, and even minor AKIs has been clinically recognized. Recent studies have shown that patients who develop AKI have a worse prognosis. The aim of this thesis was to further investigate the risk factors for and outcomes of AKI in patients undergoing cardiac surgery.

Patients and methods: Patients undergoing cardiac surgery were studied. The cohorts were identified using the SWEDEHEART register. The first study was performed to investigate whether prophylactic use of the antibiotic teicoplanin is associated with an increased risk of AKI (n = 2809 patients). The second study was performed to investigate whether type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) are risk factors for the development of AKI after coronary artery bypass grafting (CABG) (n = 36,106 patients). The third study was carried out to determine whether patients who developed AKI after CABG had an increased long-term risk for developing heart failure (n = 24,018 patients). Finally, the fourth study was performed to investigate whether even minimal increases in the SCr concentration after CABG are associated with long- and short-term mortality and the composite outcome of long-term mortality, heart failure, myocardial infarction, and stroke (n = 25,686 patients).

Results: Antibiotic prophylaxis with teicoplanin was associated with an increased risk of AKI after cardiac surgery. Additionally, a dose-dependent relationship was identified where a 600-mg dose had a higher odds ratio (OR) than a 400-mg dose of teicoplanin. Both patients with T1DM and T2DM had a significantly higher risk of developing AKI after CABG than patients without diabetes; patients with T1DM had a higher risk than those with T2DM. Patients who developed AKI after CABG had an increased long-term risk of developing heart failure. AKI was also associated with increased long- and short-term mortality and an increased risk of the combined outcome of long-term mortality, heart failure, myocardial infarction, or stroke. Even minimal increases in the SCr concentration of 0 to 26 μmol/L was associated with increased long-term mortality, and the combined outcome, but was not associated with short-term mortality.

Conclusion: Patients treated with teicoplanin and patients with T1DM or T2DM are at an increased risk of developing AKI in cardiac surgery. Patients developing AKI after CABG have an increased long-term risk of developing heart failure. Minimal increases in serum creatinine is associated with an increased long-term risk of death and cardiovascular events. AKI but not minimal increases in SCr was associated with increased 30-day mortality.