Baroreceptors in preterm infants: their relationship to maturity and disease.

Using passive tipping to a 45 degrees head-up position, an attempt was made to elicit reflex vasoconstriction in 13 non-distressed preterm infants and 27 infants with hyaline membrane disease, all between 26 and 38 weeks gestation. An increase in vascular tone associated with a significant reduction in peripheral blood-flow was found in 11 of the 13 non-distressed infants, while the same response was lacking in 23 of the 27 distressed infants. No infant demonstrated significant tachycardia with tilting, and the non-distressed infants failed to maintain their mean aortic blood-pressure during tilting. The results suggest that reflex control of vascular tone is present in non-distressed infants as early as 26 weeks gestation, but not in infats with hyaline membrane disease, possibly because of a maximal increase in vascular tone as a response to illness. This is indicated by the findings of significantly higher resting peripheral vascular resistance and lower peripheral blood-flow in infants with this diesease.