MESENTERIC BLOOD-FLOW VELOCITY AND ITS RELATION TO TRANSITIONAL CIRCULATORY ADAPTATION IN APPROPRIATE FOR GESTATIONAL-AGE PRETERM INFANTS

We investigated the early postnatal changes of the mesenteric circulat ion and its relation to the systemic circulation in 15 preterm infants . The infants were studied before the first feeding on d 1 and pre- an d postprandially on d 3, 4, 5, and 7. Blood flow velocity was measured by ultrasound Doppler in the superior mesenteric artery, middle cereb ral artery, and the aortic orifice for cardiac output calculations. Bl ood pressure and heart rate were monitored. From d 1 to d 3, the prepr andial stroke volume decreased [1.5 +/- 0.3 to 1.3 +/- 0.2 mL/kg (mean +/- SD), p < 0.05], whereas blood pressure (36 +/- 3 to 50 +/- 7 mm H g, p < 0.001), superior mesenteric artery mean velocity (V-mean) (0.17 +/- 0.08 to 0.30 +/- 0.11 m/s, p < 0.05), and middle cerebral artery V-mean increased (0.15 +/- 0.05 to 0.22 +/- 0.03 m/s, p < 0.001). From d 3 through d 7, the preterm infants demonstrated higher preprandial end diastolic flow velocity in the superior mesenteric artery than we previously reported in term infants (0.15 +/- 0.05 versus 0.12 +/- 0.0 4, p < 0.05). Like the term infants, preterm infants increased their s uperior mesenteric artery V-mean by 83% postprandially and maintained a stable cerebral circulation with feeding. Unlike the term infants, f eeding in the preterm infants induced a blood pressure decrease (51 +/ - 6 to 48 +/- 6 mm Hg, p < 0.01) and a cardiac output increase (176 +/ - 30 to 188 +/- 32 ml/kg/min, p < 0.001). These findings suggest that, in contrast to term infants, healthy preterm infants require compensa tory systemic hemodynamic changes in response to feeding.