Abstract

The peripheral perfusion index (PPI) is a non-invasive indicator of peripheral tissue perfusion in neonates. However, reference values for the PPI at different postnatal time points in healthy neonates residing at high altitudes, as well as early perfusion characteristics in infants with congenital heart disease (CHD) in these settings, remain inadequately defined. The primary aim was to determine the dynamic changes in and percentile-based reference values of the PPI in healthy neonates during the first 6–72 h after birth in the high-altitude region of Tibet. A secondary, exploratory aim was to observe PPI patterns in neonates with CHD born during the same period and to compare the two groups, given the limited number of CHD cases enrolled. A longitudinal cohort study was conducted among consecutively born neonates in a high-altitude region of Tibet. The PPI was measured in the right hand (pre-ductal) and either foot (post-ductal) at 6, ~12, ~24, ~48, and ~72 h after birth. Generalized Additive Models for Location, Scale and Shape (GAMLSS) were used to construct percentile reference curves for healthy neonates. Generalized Estimating Equations (GEE) were applied to evaluate differences in the PPI across time points, measurement sites, and between groups (healthy vs. CHD). A total of 1043 neonates were enrolled, including 1034 in the healthy group and only 9 CHD cases. In healthy neonates, the PPI increased progressively within the first 72 h, with a rapid rise from 6 to 24 h, a slower increase from 24 to 48 h, and stabilization between 48 and 72 h. At all time points, the lower-limb PPI was significantly higher than the upper-limb PPI (p < 0.001). The 50th percentile (P50) values for the upper-limb PPI at 6, 12, 24, 48, and 72 h were 2.32, 2.46, 2.62, 2.63, and 2.77, respectively; corresponding values for the lower-limb PPI were 2.53, 2.64, 2.76, 2.77, and 2.90. Compared to the healthy group, neonates with CHD at high altitudes had similar PPI at 6 h. However, their PPI was significantly lower between 12 and 48 h. At 72 h, no statistically significant difference was found between the groups, likely due to the small sample size of CHD infants. Conclusions: This study provides a reference for routine perfusion assessment in stable neonates born at high altitudes. Due to the limited sample size (only 9 CHD cases), our findings on PPI changes in neonates with CHD remain preliminary. The normative PPI percentile curves established in this study offer objective baseline perfusion data for stable neonates living in high-altitude areas. Future large-scale cohort studies are still needed to validate the clinical value of the PPI as a perfusion monitoring tool in infants with CHD.

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