Acute kidney injury early after heart transplantation: Incidence, risk factors and clinical consequences

Orthotopic heart transplantation is the primary surgical treatment for patients with end stage heart failure. The most important criterion that reflects the long term success of transplantation is survival. As in many clinical situations, acute kidney injury(AKI) is another factor that affects morbidity, mortality and long-term survival outside hospital after heart transplantation. For this reason, determination of the incidence for AKI, its perioperative risk factors and clinical outcomes are of great importance for heart transplant recipients in the postoperative period. The aim of this study was to investigate the incidence of AKI in early postoperative period after orthotopic cardiac transplantation, and to find out its related risk factors according to criteria of Kidney Disease Improving Global Outcomes (KDIGO). In addition, in order to identify the clinical outcomes, the use of renal replacement therapy (RRT), postoperative intensive care unit (ICU) stay and hospital stay and mortality were evaluated. A total of 119 orthotopic heart transplantations with the diagnosis of end stage heart failure were performed between February 2003 and April 2017 at Ankara Hospital of Baskent University School of Medicine. The patients' data were retrospectively reviewed from patient files and electronic patient records. The exclusion criteria were the following: age˂14years, known history of chronic renal failure, occurrence of preoperative RRT, and intraoperative or within the first 24 hours after surgery mortality. The study population was composed of 83 patients with a mean age of 37.9±15.5years. Sixty two (75%) of the patients were men, and the mean body mass index was 23.1±5.1 kg/m². Dilated cardiomyopathy (CMP) was observed in 37 patients (44.8%) whereas ischemic CMP in 25 patients (30.1%). Postoperative AKI was seen in 53 patients (63.9%). Of these 19 (35.8%) were stage 1, twenty (37.8%) were stage 2 and 14 (26.4%) were stage 3 in accordance with the KDIGO classification. Renal replacement therapy was applied in 39 patients (73.6%) with AKI, 30 (76.9%) of whom required continuous RRT (CRRT) and the rest [9 (23.1%)] required intermittent hemodialysis. Mean intensive care unit stay and mean length of hospital stay were calculated as 15.7±21.5days and 38.3±42.1days, respectively. The comparison between the demographic characteristics of the patients with and without AKI showed statistical significance for older age and higher BMI values in patients with AKI (p<0.05). Moreover, the incidence of coronary artery disease (p=0.035) and EuroSCORE (p=0.01) were found to be high in AKI patients. Preoperative serum blood urea nitrogen, creatinine, total and direct bilirubin values were also higher in patients with AKI (p<0.05). Echocardiographic evaluation showed that patients who had high pulmonary artery pressures and who had low ejection fractions were found to have a higher incidence of AKI (p<0.05). Low urine output, longer duration of cardiopulmonary bypass and having had higher doses of adrenaline infusion was associated with higher AKI incidence throughout the surgery (p<0.05). At the postoperative period; transfusions of erythrocyte and platelet suspensions, and albumin use was more frequent; mechanical ventilation duration and ICU stay was longer in patients with AKI (p<0.05). The 30-day and 1-year mortality rates were found to be higher in AKI patients (p<0.05). EuroSCORE, low urine output during surgery, postoperative platelet suspension transfusion and albumin use were found to be independent risk factors for AKI development after heart transplantation (p<0.05). In conclusion, this study demonstrated that the incidence of AKI was 63.9% and 46.9% of AKI patients required RRT in the early postoperative period after orthotopic heart transplantation. The duration of mechanical ventilation, the length of ICU stay, and postoperative mortality rates were high in patients with AKI. Moreover, EuroSCORE, low urine output during surgery, postoperative platelet suspension transfusion and albumin use were independent risk factors for AKI development. Awareness of the risk factors and taking perioperative precautions are of great importance for postoperative morbidity and mortality in patients with orthotopic heart transplantation.