Alice C Yao

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 circulation and its relation to the systemic circulation in 15 preterm infants. The infants were studied before the first feeding on d 1 and pre- and postprandially on d 3, 4, 5, and 7. Blood flow velocity was measured by ultrasound Doppler in the superior mesenteric artery, middle cerebral artery, and the aortic orifice for cardiac output calculations. Blood pressure and heart rate were monitored. From d 1 to d 3, the preprandial 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 Hg, p < 0.001), superior mesenteric artery mean velocity(Vmean) (0.17 ± 0.08 to 0.30 ± 0.11 m/s,p < 0.05), and middle cerebral artery Vmean 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 ± 0.04, p < 0.05). Like the term infants, preterm infants increased their superior mesenteric artery Vmean by 83% postprandially and maintained a stable cerebral circulation with feeding. Unlike the term infants, feeding 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 compensatory systemic hemodynamic changes in response to feeding.

Phototherapy-associated changes in mesenteric blood flow response to feeding in term neonates

Doppler blood flow velocity of the superior mesenteric artery was measured preprandially and postprandially in 12 term neonates during phototherapy and 4 hours after discontinuation of this therapy. The postprandial increase in blood flow velocity was significantly less during than after phototherapy. We suggest that the phototherapy-induced peripheral vasodilation may be responsible for diverting blood from the intestines and limiting the normal neonatal postprandial response.

Relationship between intrauterine growth retardation and early postnatal superior mesenteric artery blood flow velocity.

During the first week of life, we examined the changes in the systemic, intestinal and cerebral circulation, and the circulatory responses to feeding in 10 small for gestational age (SGA) infants using the ultrasound Doppler technique. From day 1 to day 3, preprandial cardiac output decreased (p < 0.01), whereas mean blood pressure (p < 0.01), superior mesenteric artery mean flow velocity (Vmean; p < 0.01) and middle cerebral artery Vmean (p < 0.01) increased. On day 1, cardiac output was higher in the SGA than in those of term and preterm appropriate for gestational age infants reported from our laboratory. Preprandial superior mesenteric artery Vmean was inversely related to the degree of growth retardation (r = 0.63, p < 0.05). However, growth retardation did not influence the postprandial increase in superior mesenteric artery Vmean and end-diastolic flow velocity, or the cerebral circulation.

Blood Flow in the Umbilical Vessels during the Third Stage of Labor

Blood flow in the umbilical vessels during third stage of labor was studied in 62 normal-term deliveries. Placental residual blood volume (PRBV) was measured as an indicator of net flow of blood into

PERIPHERAL CIRCULATORY RESPONSE TO PHOTOTHERAPY IN NEWBORN INFANTS

Calf blood flow (CBF), calf skin temperature, incubator wall and ambient temperature, and respiratory rate, were measured in 8 newborn infants 10 to 127 hours of age, who were treated by phototherapy because of jaundice. During phototherapy (within 30 min) the CBF increased to a range of 30 to 80% above the control values of 8.8 ± 0.9 ml/min/100 g. The CBF is correlated directly with the leg skin temperature (γ= 0.724 and 0.588 at 15 and 30 min after phototherapy respectively). The increase in CBF was associated with a fall in incubator ambient temperature, the latter is a result of the use of servo control unit in monitoring incubator temperature by epigastric skin temperature. The increase in CBF is probably evidence of peripheral vasodilatation to facilitate evaporative heat loss. An increase in respiratory rate was also observed during phototherapy. The observed increase in heat loss (and water loss) from vasodilatation and increased respiratory rate serve as a basis for the increase in insensible water loss as previously reported.

Atropine Prevents Increases in Brain Blood Flow during Hypertension in Newborn Piglets

ABSTRACT. Cerebral hyperperfusion associated with hypertension, may play an important role in the pathogenesis of intraventricular hemorrhage in preterm infants. To examine the effect of hypertension on changes in total and regional brain blood flow (BBF), we increased the mean arterial blood pressure (MABP) in nine awake newborn piglets by an infusion of 0.7 mg/kg of metaraminol bitar-trate (Aramine) (group I) and studied cerebral circulatory changes. In order to prevent the Aramine-associated bradycardia, we pretreated nine other piglets with atropine, which produced a higher level of hypertension (group II). MABP and BBF were measured and cerebral vascular resistance (CVR) was calculated during baseline, the Aramine infusion, and twice at decreasing MABP following the discontinuation of the Aramine infusion. In group I, the significant increase in MABP from 68 ± 3 to 100 ± 3 mm Hg (mean ± SEM) during the Aramine infusion resulted in a significant increase in BBF (98 ± 9 to 118 ± 11 ml-min−1 100 g−1)- MABP decreased significantly (although remained significantly above baseline levels), when Aramine was discontinued; however, total BBF remained elevated. CVR increased during the Aramine infusion, but decreased significan (versus the Aramine-infused state) in the post-Aramine period. Regional BBF increased significantly to the cerebrum and cerebellar cortex, but remained unchanged to the other regions including the brain stem. In group II, the Aramine infusion resulted in a significantly greater increase in MABP, a sustained increase in vascular resistance, and no increase in total BBF. Thus, atropine prevents increased BBF during hypertension in the newborn piglet.

The Effect of Blood Volume Expansion on Gastrointestinal Oxygenation in Piglets

ABSTRACT: Regional and total gastrointestinal (GI) blood flow, O2 delivery, O2 extraction, and O2 consumption were measured before and after acute blood volume expansion in 2-day-old piglets. Blood flow was measured with radionuclide-labeled microspheres. Sixty minutes after a rapid transfusion of age- and hematocrit-matched piglet donor blood, 5lCr-measured blood volume increased 19% while an increase in hematocrit suggested plasma transudation to the extravascular space had occurred in response to blood volume loading. Following transfusion, total GI blood flow and O2 delivery did not change, although O2 extraction decreased by 31 ± 4%. O2 consumption by the GI tract decreased from 2.0 ± 0.19 ml O2·min-1·100 g-1 to 1.46 ± 0.24 ml O2·min-1· 100 g-1 1 h after transfusion. Feeding was then accomplished via orogastric tube to determine if animals stressed by blood volume loading would increase GI O2 consumption in response to feeding. The postprandial increase in GI O2 consumption was similar to that previously reported in newborn piglets. Therefore, in the fasting state, acute blood volume loading disrupts GI O2 transport at the capillary level and decreases GI O2 consumption. However, animals subjected to blood volume loading appear capable of increasing GI O2 consumption after feeding.

Doppler Ultrasound Prediction of Cerebral Vascular Resistance: Relative Vascular Resistance Is More Accurate than Pourcelot's Index

Doppler Ultrasound Prediction of Cerebral Vascular Resistance: Relative Vascular Resistance Is More Accurate than Pourcelots Index

EFFECTS OF LOW DOSE PROPHYLACTIC INDOMETHACIN (plndo) ON HEMODYNAMICS IN VERY LOW BIRTH WEIGHT (VLBW) INFANTS. † 1512

EFFECTS OF LOW DOSE PROPHYLACTIC INDOMETHACIN (plndo) ON HEMODYNAMICS IN VERY LOW BIRTH WEIGHT (VLBW) INFANTS. † 1512

Physiologic Patency of the Ductus Arteriosus in Newborn Low Birth Weight (LBW) Infants Is Associated with Decreased Left Middle Cerebral Artery End-Diastolic Blood Flow Velocity

Physiologic Patency of the Ductus Arteriosus in Newborn Low Birth Weight (LBW) Infants Is Associated with Decreased Left Middle Cerebral Artery End-Diastolic Blood Flow Velocity