Organ blood flow in response to infusion of arginine vasopressin in premature fetal sheep

Background: Arginine vasopressin (AVP) infusion has been shown to be a useful strategy for the management of systemic perfusion failure in premature infants. Our objective was to determine the characteristics of the blood flow redistribution induced by AVP infusion in premature fetal sheep. Methods: Nine sheep fetuses at 99 to 113 days of gestation were continuously infused with AVP. Measurement of blood flow to individual fetal organs was performed using a colored microsphere technique, with measurements performed at 30 min before and 90 min after the initiation of AVP infusions. Results: The AVP infusion significantly increased blood flow to the medulla oblongata (P < 0.05), and significantly decreased flow to the adrenal glands (from 492.0 ± 239.6 to 364.9 ± 143.3 mL/min/100 g, P < 0.05) and heart (from 592.6 ± 184.5 to 435.6 ± 137.4 mL/min/100 g, P < 0.05). The infusion significantly increased the vascular resistance in adrenal glands, kidneys, ileum, colon, heart, and cerebellum. In the brain, except for the cerebellum, no significant increase in resistance was identified. Conclusions: There was no significant response to AVP infusion in cerebral blood flow in mid-gestation fetal sheep. Our observations suggest that, under AVP stimulation, the blood flow to the adrenal glands and myocardium might be decreased due to an increase in vascular resistance.