Fetal O2 consumption in sheep during controlled long-term reductions in umbilical blood flow

Electromagnetic flow sensors and inflatable occluders were placed on the distal aortas of nine fetal lambs of 111-124 days gestation; indwelling vascular catheters were placed in a lower body artery and vein and the common umbilical vein. After a control period of 7.6 +/- 2.1 (SD) days, distal aortic flow was reduced to about 60% of control flow; placental flow fractions of distal aortic flow were 77 +/- 5%, control; 69 +/- 11% during flow reduction. Duration of the flow reductions was 9.6 +/- 6.5 days. Fetal O2 consumption fell from 6.4 +/- 1.5 to 5.3 +/- 1.1 ml X min-1 X kg-1 (P less than 0.02) as umbilical blood flow was reduced from 202 +/- 47 to 116 +/- 36 ml X min-1 X kg-1 (P less than 0.001). Least-squares polynomial regression analysis showed that O2 consumption was a linear function of umbilical blood flow (P less than 0.01). With regard to long-term fetal O2 consumption, there was no evidence for a margin of safety in fetal umbilical blood flow.

Download Full-text

Fetal neuromuscular blockade: effect on oxygen demand and placental transport

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1989.257.3.h734 ◽

1989 ◽

Vol 257 (3) ◽

pp. H734-H738

Author(s):

R. B. Wilkening ◽

D. W. Boyle ◽

G. Meschia

Keyword(s):

Blood Flow ◽

Oxygen Saturation ◽

Neuromuscular Blockade ◽

Umbilical Vein ◽

Oxygen Demand ◽

Arterial Oxygen ◽

Uterine Blood Flow ◽

Umbilical Blood ◽

Steady State Method ◽

Umbilical Blood Flow

To study mechanisms by which variations in fetal oxygen demand alter fetal oxygen saturation and PO2, we measured uterine and umbilical blood flow and transplacental oxygen diffusion rate in eight chronically prepared pregnant ewes before and during fetal neuromuscular blockade with pancuronium bromide (0.2 mg/kg). Uterine and umbilical blood flows were measured by applying the steady-state method using ethanol as the test substance. Fetal oxygen uptake decreased 7.5% (P less than 0.05). Umbilical blood flow increased 6% (P less than 0.05), whereas uterine blood flow did not change significantly. Fetal arterial oxygen saturation increased markedly (54.8–60.9%; P less than 0.001). There were also significant increases in umbilical vein oxygen saturation (83.6–86.9%; P less than 0.01), uterine vein oxygen saturation (70.7–72.2%; P less than 0.01), umbilical vein PO2 (29.4–32.1 Torr; P less than 0.001), and uterine vein PO2 (49.4–50.7 Torr; P less than 0.01). The uterine-umbilical venous PO2 difference decreased significantly (20.0–18.6 Torr; P less than 0.001), whereas there was no significant change in the uterine-umbilical venous PCO2 difference or in the umbilical ethanol shunt. The data indicate that follows a small decrease in fetal oxygen demand is caused by two aspects of placental oxygen transport: 1) umbilical and uterine blood flow do not react homeostatically to prevent the rise of PO2 in the placental circulation, and 2) the decrease in oxygen flux from placenta to fetus is associated with a decrease in the transplacental PO2 gradient.

Download Full-text

Increased oxygen consumption associated with breathing activity in fetal lambs

Journal of Applied Physiology ◽

10.1152/jappl.1983.54.3.701 ◽

1983 ◽

Vol 54 (3) ◽

pp. 701-707 ◽

Cited By ~ 33

Author(s):

D. W. Rurak ◽

N. C. Gruber

Keyword(s):

Blood Flow ◽

Large Amplitude ◽

O2 Consumption ◽

Blood Gas ◽

Control Value ◽

Umbilical Blood ◽

Fetal Breathing ◽

Fetal Breathing Movements ◽

Umbilical Blood Flow ◽

Low Amplitude

To examine the relationship between fetal O2 consumption and fetal breathing movements, we measured O2 consumption, umbilical blood flow, and cardiovascular and blood gas data before, during, and after fetal breathing movements in conscious chronically catheterized fetal lambs. During fetal breathing movements, O2 consumption increased by 30% from a control value of 7.7 +/- 0.7 (SE) ml X min-1 X kg-1. Umbilical blood flow was 210 +/- 21 ml X min-1 X kg-1 before fetal breathing movements; in 9 of 16 samples it increased by 52 +/- 12 ml X min-1 X kg-1, while in the other 7 it decreased by 23 +/- 9 ml X min-1 X kg-1. Umbilical arterial and venous O2 partial pressures and pH fell during fetal breathing movements, and the fall was greater when umbilical blood flow was decreased. Partial CO2 pressure rose in both vessels, and again the increase was greatest when umbilical blood flow fell during fetal breathing movements. Also associated with a fall in umbilical blood flow was the transition from low-amplitude irregular to large-amplitude regular fetal breathing movements. It is concluded that fetal breathing movements increase fetal O2 demands and are associated with a transient deterioration in fetal blood gas status, which is most severe during large-amplitude breathing movements.

Download Full-text

Absence of fetal placental waterfall phenomenon in chronically prepared fetal lambs

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1976.230.4.886 ◽

1976 ◽

Vol 230 (4) ◽

pp. 886-892 ◽

Cited By ~ 14

Author(s):

KL Thornburg ◽

JM Bissonnette ◽

JJ Faber

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Arterial Blood Pressure ◽

Umbilical Vein ◽

Venous Pressure ◽

Amniotic Cavity ◽

Umbilical Blood ◽

Arterial Blood ◽

Placental Blood ◽

Umbilical Blood Flow

An electromagnetic flow sensor was placed on the distal fetal aorta (umbilical flow fraction 78.1 +/- 1.6 SEM, %), an inflatable occluder was tied around the umbilical cord, and catheters were placed in distal branches of an umbilical artery and vein, a uterine vein, and in the amniotic cavity. An inflatalbe occluder was tied around the vagina of some of the ewes. Control values 3 days after surgery were (mean +/- SE): fetal femoral artery pH, 7.37 +/- 0.01; umbilical blood flow, 186 +/- 14 ml-min-1 .kg fetus-1; fetal arterial blood pressure, 39 +/- 3 mmHg; and umbilical venous pressure, 7.4 +/- 1.0 mmHg (above intrauterine pressure). Fetal weight at autopsy was 3.1 +/- 0.3 kg, n = 11. Small increases in umbilical vein pressure caused immediate decreases in placental blood flow without decreases in fetal arterial blood pressure. The relation between venous pressure and umbilical blood flow at constant arterial pressure was that of an inert system, i.e., no evidence of a surrounding pressure (Starling resistor effect or waterfall phenomenon) could be found with increases in venous pressures of 2-40 mmHg. The results were not affected by increases in uterine vein pressure between 2 and 30 mmHg, nor by anesthesia and supine position of the ewe, nor by ganglionic blockade of the fetal ANS. It was concluded that surrounding pressures in the fetal placental circulation could not be demonstrated.

Download Full-text

Altered umbilical blood flow after treatment with betamethasone in compromised preterm pregnancies

Journal of the Society for Gynecologic Investigation ◽

10.1016/s1071-5576(97)86424-6 ◽

1998 ◽

Vol 5 (1) ◽

pp. 123A-123A

Author(s):

L BAKER ◽

E WALLACE

Keyword(s):

Blood Flow ◽

Umbilical Blood ◽

Umbilical Blood Flow

Download Full-text

Placental transfer as a function of uterine blood flow

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1982.242.3.h429 ◽

1982 ◽

Vol 242 (3) ◽

pp. H429-H436 ◽

Cited By ~ 2

Author(s):

R. B. Wilkening ◽

S. Anderson ◽

L. Martensson ◽

G. Meschia

Keyword(s):

Blood Flow ◽

Placental Transfer ◽

Appreciable Effect ◽

Uterine Blood Flow ◽

Placental Perfusion ◽

Umbilical Blood ◽

Norepinephrine Infusion ◽

Umbilical Blood Flow ◽

Clearance Level ◽

Different Levels

The effect of variations of uterine blood flow (F) on placental transfer was examined in six chronic sheep preparations by measuring the placental clearances of ethanol (CE) and antipyrine (CA) at different levels of F. Norepinephrine infusion, hemorrhage, and occlusion of the terminal aorta were used to reduce F below normal. The reduction of F had no appreciable effect on umbilical blood flow (f). In each ewe, CE significantly correlated with F. The CE vs. F relationship at constant f was curvilinear with convexity toward the clearance axis. Regression analysis showed that the equation 1/CE = 1/.911 F + 1/.831 f could account for most of the CE variance (r2 = 0.97). Implicit in this relation is the concept that, given a certain level of placental perfusion, an F/f ratio congruent to 1 is optimal for the exchange of highly diffusible inert molecules between mother and fetus [CE/(F + f) was maximum at F/f = 0.955]. CA was not significantly different from CE at low clearance level but became smaller than CE at clearance values greater than 300 ml/min. This suggests that a high rates of perfusion placental permeability was a factor in limiting CA.

Download Full-text

CSH RNA Interference Reduces Global Nutrient Uptake and Umbilical Blood Flow Resulting in Intrauterine Growth Restriction

International Journal of Molecular Sciences ◽

10.3390/ijms22158150 ◽

2021 ◽

Vol 22 (15) ◽

pp. 8150

Author(s):

Amelia R. Tanner ◽

Cameron S. Lynch ◽

Victoria C. Kennedy ◽

Asghar Ali ◽

Quinton A. Winger ◽

...

Keyword(s):

Blood Flow ◽

Rna Interference ◽

Nutrient Uptake ◽

Intrauterine Growth Restriction ◽

Growth Restriction ◽

Intrauterine Growth ◽

Umbilical Blood ◽

Uterine Growth ◽

Umbilical Blood Flow ◽

Placental Hormone

Deficiency of the placental hormone chorionic somatomammotropin (CSH) can lead to the development of intrauterine growth restriction (IUGR). To gain insight into the physiological consequences of CSH RNA interference (RNAi), the trophectoderm of hatched blastocysts (nine days of gestational age; dGA) was infected with a lentivirus expressing either a scrambled control or CSH-specific shRNA, prior to transfer into synchronized recipient sheep. At 90 dGA, umbilical hemodynamics and fetal measurements were assessed by Doppler ultrasonography. At 120 dGA, pregnancies were fitted with vascular catheters to undergo steady-state metabolic studies with the 3H2O transplacental diffusion technique at 130 dGA. Nutrient uptake rates were determined and tissues were subsequently harvested at necropsy. CSH RNAi reduced (p ≤ 0.05) both fetal and uterine weights as well as umbilical blood flow (mL/min). This ultimately resulted in reduced (p ≤ 0.01) umbilical IGF1 concentrations, as well as reduced umbilical nutrient uptakes (p ≤ 0.05) in CSH RNAi pregnancies. CSH RNAi also reduced (p ≤ 0.05) uterine nutrient uptakes as well as uteroplacental glucose utilization. These data suggest that CSH is necessary to facilitate adequate blood flow for the uptake of oxygen, oxidative substrates, and hormones essential to support fetal and uterine growth.

Download Full-text