In the present study, we retrospectively evaluated the clinical efficacy of IHD for CKD patients undergoing cardiac surgery. No significant differences were observed in the outcomes between the IHD group and the non-IHD group. However, the rate of postoperative RRT initiation in patients with CKD G4 was significantly lower in IHD group than the non-IHD group despite the lower renal function before operation and the higher blood transfusion volume.
The development of AKI after cardiac surgery (particularly, cardiopulmonary bypass surgery), is associated with prolonged ICU and hospital stay and an increased risk of death [11–15]. Many patients have multiple organ failure, thereby requiring assisted ventilation, intra-aortic balloon counterpulsation, continuous inotropic medication, and at times, the use of extracorporeal life support. It has been estimated that among patients who required hemodialysis recently, 64% required permanent dialysis, and up to 90 % died within 1 year [16, 17]. Additionally, the patients with acute CKD after surgery possibly require maintenance hemodialysis. Therefore, the treatment of severe AKI after surgery, particularly cardiac surgery, is very important.
Durmaz et al. reported that perioperative prophylactic RRT decreased both operative mortality and morbidity in high-risk patients with CKD , and Sugahara et al. further reported that early initiation of RRT improved the survival of patients with AKI following cardiac surgery . Thus, prophylactic or early RRT may be useful for CKD patients after cardiac surgery.
In addition, multiple strategies have been commonly used to improve the intraoperative AKI. The use of dopamine, furosemide, fenoldopam, and human atrial natriuretic peptide has been shown to prevent AKI [20, 21]. In the present study, perioperative drugs therapy, the type of surgery, and the patients’ characteristics did not differ significantly between the two groups. Further, red blood cell transfusion has been reported to be independently associated with AKI [22, 23]. In our study, IHD during open-heart surgery was associated with a significant reduction in 30-day RRT rate in patients with CKD G4, despite that they had more volume of blood transfusion and the lower renal function before operation than the patients in non-IHD group. This result is noteworthy. This may be because IHD may be associated with the removal of excess fluid, uremic toxins, and inflammatory mediators during cardiopulmonary bypass surgery.
Fluid overload was the most frequent cause of RRT initiation in our study. Fluid overload has been reported to be a risk factor for mortality and is known to cause prolonged postoperative ventilation time [24, 25]. Several studies have shown that hemofiltration in patients with AKI and cardiac shock after surgery improves cardiorespiratory function [6, 26], and metabolic acidosis has been shown to reduce cardiac output . IHD possibly causes better control of the fluid status and improves uremia and acidosis. Owing to the higher volume of blood transfusion in patients in the IHD group in our study, we suggest that IHD may be helpful for an anesthesiologist.
To the best of our knowledge, the studies investigating IHD in CKD patients undergoing cardiac surgery are rare. During liver transplantation in CKD patients, IHD has been shown to ameliorate fluid overload, acidosis, and electrolyte abnormality, and the process has been reported to be safe and effective . IHD may be helpful in achieving even or negative fluid balance with minimal hemodynamic changes during the surgery despite the presence of significant amounts of blood products and crystalloids.
Our study has a few limitations. First, the sample size was small and it was a retrospective observational study conducted at a single center. We observed no significant differences in the primary outcomes between the two groups. Second, the medical and nursing staff were different for the IHD and non-IHD groups. Particularly, the main surgeon was different for patients in IHD group and non-IHD group. However, we confirmed no difference in the duration of surgery between both the groups. Third, dialysis after surgery was initiated at the discretion of each nephrologist. However, the major cause of dialysis was fluid overload. Therefore, we suggest that the impact of nephrologist’s discretion on clinical outcomes in this study was minimal. Fourth, the definition of performing IHD for CKD patients at our institution was unclear. In our cohort, all patients with CKD G4 and G5 underwent IHD. However, the patients with CKD 3b were very small. Fifth, the perioperative infusion volume was unknown. It is possible that the anesthesiologists might have changed the strategy of infusion between both groups during the long duration of the study.