Renal near-infrared spectroscopy for assessment of renal oxygenation in adults undergoing cardiac surgery – a method validation study

Abstract Objective To investigate the correlation between invasively measured renal venous oxygen saturation (SrvO2) and tissue oxygenation (rSO2) measured with near infrared spectroscopy (NIRS) in adult patients undergoing cardiac surgery. Design Prospective observational study. Setting Single cardiac surgery centre at a University Hospital. Participants Thirteen adult patients with skin to kidney distance ≤ 4 cm undergoing open cardiac surgery with cardiopulmonary bypass (CPB). Interventions All patients received renal vein catheters for invasive measurement of SrvO2, and NIRS electrodes for assessment of renal rSO2 were placed over the kidney using ultrasound guidance. Measurements were made before, during CPB at three different flow rates (2.4, 2.7 and 3.0 L/min/m2), and after bypass. Measurements and main results Repeated measures correlation analyses and Bland-Altman plots were used to study the correlation and agreement between rSO2 and SrvO2. For all measurement points, renal rSO2 correlated with SrvO2 (rrm=0.61, p Conclusions Renal rSO2 is correlated to and predicts SrvO2 with a small bias and acceptable agreement. Further studies are needed before renal NIRS can be used as a surrogate marker of renal oxygenation in clinical practice.