RENAL BLOOD FLOW MEASUREMENT WITH TRANSESOPHAGEAL ECHOCARDIOGRAPHY:RENAL OXYGEN SATURATION AND ITS ASSOCIATION WITH ACUTE RENAL INJURY

Peri-operative renal dysfunction is a major mortality and morbidity cause following cardiac and major vascular surgery. Patients undergoing cardiac surgery with more than one risk factor for postoperative renal insufficiency develop clinical significant renal dysfunction which results in extended length of stay in 1/5 of the patients .At least50% of the postoperative renal dysfunction is associated with development of renal hypoperfusion during cardiopulmonary bypass or aortic cross clamping. Although several intra-operative strategies are proposed for better outcomes, no effective and fast resulting test is available to be done in operating rooms to assess renal functions. Urine and blood markers as serum creatinine, urine output, fractional excretion of sodium and urea are used for early diagnosis of acute renal injury. In this study definition and classification of AKI (acute kidney injury) will be done according to KDIGO (kidney disease improving global outcome) criteria.

Renal perfusion can be assessed by renal artery measurements done by ultrasound imaging.The same assessment can also be done by transesophageal echocardiography (TEE).

Near infrared spectroscopy (NIRS) assesses tissue oxygenation especially cerebral regional oxygen saturation. NIRS measures regional oxygenation (rSO=oxyhemoglobin/ total Hemoglobin) by determining oxy- and deoxy- hemoglobin signals.

The probe placed on frontotemporal region has two sensors and a light source. Data is gained from sensors 3cm apart from the extracranial tissue and 4cm apart from the brain tissue; value is formed from calculation of the difference of these data. The benefit of NIRS followups of cerebral and somatic (liver, kidney, mesentery) oxygenation in pediatric cardiovascular surgery patients are demonstrated by studies.

The investigators aimed to investigate the association of postoperative acute renal injury and the change in peroperative renal blood flow and renal oxygenation values; additionally to establish wether it can be used as a fast responding and efficient method in evaluating renal function in the operating room settings.