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

Abstract

Background: Near-infrared spectroscopy (NIRS) is being increasingly used to investigate regional oxygenation (rSO₂) and perfusion in areas such as the abdomen in preterm infants prone to feeding intolerance. Lower abdominal rSO₂ 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 rSO₂ values in stable preterm infants in response to feeding.

Study design: We prospectively evaluated the correlation between rSO₂ 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 rSO₂ values.

Results: The overall mean liver rSO₂ 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 rSO₂ appears to be a more stable surrogate for splanchnic oxygenation and perfusion than lower abdomen rSO₂.

Keywords: Feeding intolerance; Low birthweight; Near infrared spectroscopy; Necrotizing enterocolitis; Prematurity; Regional oxygenation.