Continuous monitoring of liver oxygenation with near infrared spectroscopyduring naso-gastric tube feeding in neonates

Near infrared spectroscopy(NIRS) is a non-invasive method of estimating the haemoglobin concentration changes in certain tissues. it is frequently use d to monitor oxygenation of the brain in neonates. At present it is not cle ar whether near infrared spectroscopy of other organs (e.g. the liver as a corresponding site in the splanchnic region, which reacts very sensitively to haemodynamic instability) provides reliable values on their tissue oxyge nation. The aim of the study was to test near infrared spectroscopy by meas uring known physiologic changes in tissue oxygenation of the liver in newbo rn infants during and after feeding via a naso-gastric tube. The test-retes t variability of such measurements was also determined. On 28 occasions in 25 infants we measured the tissue oxygenation index (TOI ) of the liver and the brain continuously before, during and 30 minutes aft er feeding via a gastric tube. Simultaneously we measured arterial oxygen s aturation (SaO(2)), heart rate (HR) and mean arterial blood pressure (MAP). In 10 other newborn infants we performed a test-retest analysis of the live r tissue oxygenation index to estimate the variability in repeated intra-in dividual measurements. The tissue oxygenation index of the liver increased significantly from 56.7 +/- 7.5% before to 60.3 +/- 5.6% after feeding (p < 0.005), and remained unchanged for the next 30 minutes. The tissue oxygenat ion index of the brain (62.1 +/- 9.7%), SaO(2) (94.4 +/- 7.1%), heart rate (145 +/- 17.3 min(-1)) and mean arterial blood pressure (52.8 +/- 10.2 mm H g) did not change significantly. The test-retest variability for intra-individual measurements was 2.7 +/- 2 .1%. After bolus feeding the tissue oxygenation index of the liver increase d as expected. This indicates that near infrared spectroscopy is suitable f or monitoring changes in tissue oxygenation of the liver in newborn infants .