Effects of mild and moderate hypothermia on renal injury evaluated with neutrophil gelatinase associated lipocalin cystatin C and near infrared spectroscopy in patients undergoing cardiopulmonary bypass graft surgery

BACKGROUND: The degree of hypothermia during coronary artery bypass grafting (CABG) surgery may affect kidney injury. In this study we compared the effects of mild (MLD) and moderate (MOD) hypothermia on renal injury evaluated with Neutrophil Gelatinase Associated Lipocalin (NGAL), Cystatin-C (Cyc-C) and Near Infrared Spectroscopy (NIRS) in CABG surgery. METHODS: With institutional approval, 40 adult patients CABG with CPB were divided into two groups; mild hypothermia, (320C) (MLD group) (n = 20) and moderate hypothermia (280C) (MOD group) (n = 20). Urinary NGAL and serum Cyc-c were measured preoperatively (t1) and at postoperative 6th (t2), 12th (t3), 24th (t4) and 48th (t5) hours and NIRS values were recorded during intraoperative and postoperative 12 hours, and at postoperative 24th and 48th hours. Appropriate tests were used for Statistical analysis, p < 0.05 = significant. RESULTS: AKI occurred in five patients of the MLD group and one patient in MOD group (p < 0.05). Urinary NGAL and serum Cyc-C levels were higher in MLD group (p < 0.05). No correlation existed between intraoperative NIRS values and postoperative NGAL values. Moderate correlation was found between intraoperative NIRS and postoperative Cyc-C and serum creatinine (p < 0.05). CONCLUSION: Our results indicate that MOD hypothermia is more protective regarding renal function. NIRS values are not sufficient enough in terms of clinical follow-up.