Near-infrared spectroscopy as continuous real-time monitoring for kidney graft perfusion

Background Near-infrared spectroscopy (NIRS) is a noninvasive technique designed to study regional oxygenation (rSO2) by measuring the absorption of chromophores. This study investigated the role of NIRS in the real-time monitoring of kidney graft perfusion for 72 h post-transplantation. Methods Consecutive children undergoing living related donor (LRD) or deceased donor (DD) kidney transplantation (KTP) were prospectively enrolled between April 2010 and August 2011. Renal rSO2 values were registered continuously for 3 days and correlated with hourly urine output, serum creatinine, and urinary neutrophil gelatinase-associated lipocalin (u-NGAL). Results Twenty-four children were included, 6 underwent LRD and 18 DD KTP. Median age was 12.5 years (interquartile range [IQR] 3.5–16.6) and median body weight was 37 kg (IQR 13–49.7). Four patients experienced delayed graft function (DGF). Renal Doppler ultrasound showed normal vascularization patterns in all children. Median basal renal rSO2 value was 68.8 % (IQR 59.3–76.2), significantly lower than the end-of-period result (83.6 %; IQR 79.2–90.4; p <0.0001). Renal rSO2 values showed significant correlation with serum creatinine (rs=−0.62; p <0.05) and estimated glomerular filtration rate (eGFR) (rs=0.64; p <0.05). No correlation was shown between rSO2 and diuresis. Increased rSO2 was also found in patients who experienced DGF. u-NGAL exhibited a trend toward a decrease from baseline in both DD and LRD KTPs, with a strong negative correlation with rSO2. Conclusions rSO2 assessed by NIRS strongly correlates with common markers of kidney graft function and perfusion, allowing continuous real-time monitoring of blood flow in renal grafts.