Microcirculatory mechanisms in postnatal hypotension affecting premature infants

BACKGROUND: Hypotension remains a common complication in preterm infants and is associated with high neonatal morbidity and mortality. The underlying mechanisms are still not fully understood. We studied the microcirculation in extremely low birth weight infants to understand the relationship between blood pressure and skin perfusion. METHODS: In 21 patients (gestational age <30 wk, birth weight <1,225 g), functional vessel density (FVD) and diameter distribution were obtained prospectively by side stream dark-field imaging at the right arm in the first 48 h after birth. Infants with blood pressure below gestational age and receiving catecholamines were defined as hypotensive as compared with the remaining normotensive control group. RESULTS: In the first 6h after birth, FVD was significantly higher in the hypotensive group than in the control group. After 12 h, there were no significant differences in either blood pressure or FVD between the two groups. FVD did not change significantly during the observation period in either group. CONCLUSION: Hypotensive infants have a higher FVD, possibly due to loss of microvascular tone leading to vasodilation and flow redistribution. However, the link between blood pressure and perfusion remains unclear, and no definitive correlation could be found.