Harer MW, Chock VY.Front Pediatr. 2020 May 14;8:241. doi: 10.3389/fped.2020.00241. eCollection 2020.PMID: 32528917 Free PMC article. Review.
Adequate oxygenation of the kidney is of critical importance in the neonate. Non-invasive monitoring of renal tissue oxygenation using near-infrared spectroscopy (NIRS) is a promising bedside strategy for early detection of circulatory impairment as well as recognition of specific renal injury. As a diagnostic tool, renal NIRS monitoring may allow for earlier interventions to prevent or reduce injury in various clinical scenarios in the neonatal intensive care unit. Multiple studies utilizing NIRS monitoring in preterm and term infants have provided renal tissue oxygenation values at different time points during neonatal hospitalization, and have correlated measures with ultrasound and Doppler flow data. With the establishment of normal values, studies have utilized renal tissue oxygenation monitoring in preterm neonates to predict a hemodynamically significant patent ductus arteriosus, to assess response to potentially nephrotoxic medications, to identify infants with sepsis, and to describe changes after red blood cell transfusions. Other neonatal populations being investigated with renal NIRS monitoring include growth restricted infants, those requiring delivery room resuscitation, infants with congenital heart disease, and neonates undergoing extracorporeal membrane oxygenation. Furthermore, as the recognition of acute kidney injury (AKI) and its associated morbidity and mortality in neonates has increased over the last decade, alternative methods are being investigated to diagnose AKI before changes in serum creatinine or urine output occur. Studies have utilized renal NIRS monitoring to diagnose AKI in specific populations, including neonates with hypoxic ischemic encephalopathy after birth asphyxia and in infants after cardiac bypass surgery. The use of renal tissue oxygenation monitoring to improve renal outcomes has yet to be established, but results of studies published to date suggest that it holds significant promise to function as a real time, early indicator of poor renal perfusion that may help with development of specific treatment protocols to prevent or decrease the severity of AKI.
Figure 1 Proper location of neonatal renal NIRS sensor. This image shows the proper placement of neonatal renal NIRS sensor below the costal margin and above the iliac crest with the tip of the sensor lateral to the spine and reading end of the sensor wrapping around the side.
Figure 2 Estimated normal term neonatal renal tissue oxygenation in the first 48 h. This figure depicts predicted normal values of renal tissue oxygenation in term babies during the first 48 h of life based on studies done by Montaldo and Bailey (16, 17). The first 15 min of data are mean values from the Montaldo et al. study and the remaining data are median values from the Bailey et al. study.
Figure 3 Estimated normal preterm neonatal renal tissue oxygenation in the first 21 days. This figure depicts predicted normal values of renal tissue oxygenation in preterm babies during the first 21 days of life based on studies done by Richter and McNeil (15, 18). For the first 48 h, data combined from all 4 groups of the Richter et al. study are expressed as median and interquartile range while for days 3–21 data are extrapolated from the McNeil et al. study that were presented as mean and standard deviation.
Figure 4 Therapeutic window created by monitoring renal tissue oxygenation. This figure shows the theoretical timeline of changes in a patient with acute kidney injury. Initially tissue oxygenation changes occur followed by a later decrease in urine output and an increase in serum creatinine. Changes in urine output and serum creatinine may signal permanent tissue injury, while changes in tissue oxygenation may reflect an earlier time period when renal ischemia is still reversible and responsive to fluid management, transfusions, inotropic support, or medication administration that may resolve ongoing injury.