Comparing liver and lower abdomen near-infrared spectroscopy in preterm infants

Background: Near-infrared spectroscopy (NIRS) is being increasingly used to investigate regional oxygenation (rSO(2)) and perfusion in areas such as the abdomen in preterm infants prone to feeding intolerance. Lower abdominal rSO(2) values are extremely variable, high sensitivity and currently low specificity tools. The liver, a solid organ, could provide a more reliable site for splanchnic oxygenation and perfusion monitoring. Aims: Compare liver and lower abdomen rSO(2) values in stable preterm infants in response to feeding. Study design:We prospectively evaluated the correlation between rSO(2) over the liver and lower abdomen in 16 preterm infants born between 28 and 32 weeks' gestational age using 48 h of continuous NIRS data. Outcome measures: Mean liver and lower abdomen rSO(2) values. Results: The overall mean liver rSO(2) were higher than the overall mean lower abdomen values, 78.4 7.1 vs. 65.1 +/- 24.9 respectively. Time series analysis showed a mean maximum cross correlation between the liver and lower abdomen of 0.28 (SD +/- 0.03; p < 0.001); the liver signal lagged the lower abdomen by an average of 5.4 s (SD +/- 1.2 s, Range 0-16 s). Mixed models analysis showed that during bolus feeding, liver values increased 10 to 30 min after the start of feeding (p < 0.01) while lower abdomen increased from 20 to 60 min after the start of feeding (p < 0.05) and liver values were less variable than lower abdomen values. Conclusion: Liver rSO(2) appears to be a more stable surrogate for splanchnic oxygenation and perfusion than lower abdomen rSO(2).