5.1 Chronic Kidney disease
AKI is recognized to be a strong independent risk factor for CKD progression.33 Based on the KDIGO guidelines, the diagnosis for CKD is confirmed by at least two eGFR values of ≤60 ml min-1 (1.73m)-2 separated by at least 90 days. According to one study on patients with reversible AKI, the hazard ratio for CKD development was 2.3 in contrast to patients without AKI.35 This is a serious concern especially after cardiac surgery, due to the poor cardiovascular morbidity and mortality associated with CKD.
The transition from acute kidney disease to CKD is known as “maladaptive repair”. This pathway is characterised by persistent parenchymal inflammation, G2/M arrest in tubular epithelial cells, and epigenetic reprogramming of myofibroblasts which predisposes the kidneys to fibrosis and ultimately CKD. 37 Similar to CS-AKI, risk factors for the progression of CKD include having a pre-operative eGFR <80 ml min-1 (1.73m)-2, advancing age (>65yr), type of surgery; aortic surgery or heart transplantation, and an aortic clamping time greater than 50 minutes. Other recurring features they observed among surgical patients with postoperative CKD were that they typically had a higher BMI, were hypertensive, and received more blood transfusion during the intraoperative period.38
Moreover, previous studies have highlighted the use of norepinephrine during CPB as another potential risk factor for CKD. Generally, norepinephrine is known to improve renal function in sepsis by promoting creatinine clearance and urine output. However, norepinephrine can also reduce medullary perfusion and oxygen tension, thus causing secondary renal hypoxia injury and diminished renal function.39This is of particular concern for patients with congenital heart disease (CHD) undergoing cardiac surgery.40 It is probable that a combination of any of these risk factors along with the patient’s predisposing factors may influence their susceptibility to CKD progression. Table 3 summarises the patient and procedure-related risk factors that result in chronic kidney disease and ESRD.