The relationship between renal oxygen saturation and renal function in patients with and without diabetes following coronary artery bypass grafting surgery

Abstract

Background/Aim: Acute kidney injury may occur due to renal ischemia and hypoxia during coronary artery bypass surgery. Monitoring of renal regional tissue oxygenation might be useful to determine renal hypoxia. We aimed to investigate whether renal oxygen saturation values differ between diabetic and non-diabetic patients and evaluate the relationship between intra-operative renal oxygen saturation values and postoperative renal function. Methods: Forty consecutive patients aged 18-65 years, who underwent elective coronary artery bypass grafting, were included in this prospective case-control study. Body mass index ≥30 kg/m2 and the presence of renal damage were considered the exclusion criteria. Group I consisted of diabetic patients (n = 20), and Group II consisted of non-diabetic patients (n = 20). Near Infrared Spectroscopy (NIRS) recorded renal saturation values just before the intubation as the basal value and every 10 minutes after intubation in all patients. Creatinine clearances and glomerular filtration rates were calculated along with blood urea nitrogen and creatinine values on the postoperative 1st and 3rd days of all patients. Results: The two groups were similar in terms of gender, age, body mass index, duration of surgery, cross-clamp time, and total cardiopulmonary bypass duration (P>0.05). While there was no difference between baseline values, significant differences were found between preoperative BUN and creatinine and POD 3 BUN and creatinine values in Group 1 (P=0.003 and P=0.046, respectively) and Group 2 (P=0.018 and P=0.030, respectively). There was no significant difference between two groups in renal oxygen saturation values considering both basal and post-intubation measurements (P>0.05 for all). However, an earlier decrease in renal oxygen saturation values was seen in diabetic patients (P<0.05). There was no significant relationship between the changes in intraoperative renal oxygen saturation values and postoperative renal function (P>0.05 for all). Conclusion: Although coronary artery graft bypass surgery does not lead to a significant difference in renal saturation values, as determined by Near Infrared Spectroscopy, in diabetic patients compared to non-diabetic patients, NIRS may be helpful and beneficial to show renal ischemia in these patients.