Decreased urine production in the near-term fetal lamb after maternal ethanol infusion

The acid-base status of the fetal lamb was studied in near-term pregnant ewes subjected to spinal anesthesia. The status of the fetus was compared to its mother and the changes which occur after the fetal lungs were ventilated with oxygen or nitrogen were investigated. The results show that: 1) the fetus in utero is in a state of metabolic acidosis in relation to the mother, 2) the acidosis does not seem to be related to the fetal blood pCO2, and 3) the acidosis may be aggravated by hypoxia. fetal acidosis; blood pH; blood oxygen; blood carbon dioxide; hypoxia; hyperoxia; sheep Submitted on March 20, 1963

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Major contribution of central pulmonary reservoir discharge to increased pulmonary arterial diastolic blood flow after birth in near-term lambs

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00077.2016 ◽

2016 ◽

Vol 311 (4) ◽

pp. R702-R709 ◽

Cited By ~ 5

Author(s):

Joseph J. Smolich ◽

Jonathan P. Mynard

Keyword(s):

Blood Flow ◽

Left Atrial ◽

Pulmonary Trunk ◽

Pulmonary Perfusion ◽

Flow Profile ◽

Cesarean Section Delivery ◽

Time Flow ◽

Fetal Lamb ◽

Pulmonary Arterial ◽

Near Term

Recent fetal lamb data have suggested that the pulmonary trunk (PT) region displays a reservoir function and that a pharmacologically induced fall in pulmonary vascular resistance (PVR) increases and redistributes diastolic discharge from this central pulmonary reservoir toward the lungs, thereby producing a positive diastolic offset in the pulmonary arterial (PA) blood flow profile. As a similar offset in PA flow characteristically occurs after birth, this study tested the hypotheses that 1) central pulmonary reservoir discharge is both redistributed toward the lungs and increased in magnitude during the birth transition and 2) discharge from this reservoir constitutes a major component of increased PA diastolic blood flow after birth. Six anesthetized near-term fetal lambs were instrumented with PT, ductal and left PA transit-time flow probes, and aortic, PT and left atrial catheters. Hemodynamic data were recorded in fetuses and at regular intervals during 2-h mechanical ventilation following cesarean section delivery. Diastolic PA blood flow rose from near zero in fetuses to 468 ± 188 ml/min by 15 min ( P < 0.001). Central pulmonary reservoir discharge in fetuses (99 ± 44 ml/min) passed primarily right-to-left across the ductus. However, this reservoir discharge redistributed entirely to the lungs by 1 min after birth, and then doubled to a peak of 214 ± 167 ml/min at 15 min ( P < 0.001). Reservoir discharge subsequently stabilized at 151 ± 60 ml/min at 30–120 min, which comprised ∼50% of diastolic and ∼20% of mean PA blood flow. These findings suggest that enhanced diastolic central pulmonary reservoir discharge plays a major role in supporting an increased pulmonary perfusion after birth.

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Effect of ventilation on pulmonary blood volume of the fetal lamb

Journal of Applied Physiology ◽

10.1152/jappl.1975.39.6.969 ◽

1975 ◽

Vol 39 (6) ◽

pp. 969-975 ◽

Cited By ~ 10

Author(s):

A. M. Walker ◽

D. G. Alcorn ◽

J. C. Cannata ◽

J. E. Maloney ◽

B. C. Ritchie

Keyword(s):

Blood Flow ◽

Blood Volume ◽

Common Factor ◽

Fetal Lung ◽

Volume Changes ◽

Pulmonary Blood Volume ◽

Fetal Lamb ◽

Air Ventilation ◽

Near Term ◽

Blood Cell And Plasma

Blood volume changes in the fetal lung following the onset of ventilation were studied by isotopic measurement of red blood cell and plasma volume in rapidly frozen lungs of ten near term fetal lambs. Total pulmonary blood volumes of fetal lambs ventilated with 3% O2 and 7% CO2 in nitrogen (so that blood gas levels were little changed from fetal values), or with air, were compared with measurements in unventilated lambs. Regional correlations of blood volume and blood flow (measured with isotope-labeled microemboli) within the lungs were also examined. Total pulmonary blood volume averaged 5.6 ml/kg body weight in unventilated fetal lambs and was approximately 43% greated in fetal lambs after 5–20 min of air ventilation, but not significantly different in lambs ventilated with 3% O2 and 7% CO2 in nitrogen. Thus it is ventilation with air, rather than the introduction of gas into the alveoli, which enlarges the fetal pulmonary vascular bed. Regional pulmonary blood volume and blood flow were correlated, though poorly, in air-ventilated lungs, but not in lungs ventilated with 3% O2 and 7% CO2 in nitrogen; this suggests that a common factor may operate to increase both blood flow and blood volume in the fetal lung following the introduction of air.

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Development of pulmonary vascular response to oxygen

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1988.254.3.h542 ◽

1988 ◽

Vol 254 (3) ◽

pp. H542-H546 ◽

Cited By ~ 23

Author(s):

F. C. Morin ◽

E. A. Egan ◽

W. Ferguson ◽

C. E. Lundgren

Keyword(s):

Blood Flow ◽

Right Ventricular ◽

Oxygen Tension ◽

Pulmonary Circulation ◽

Pulmonary Blood Flow ◽

Arterial Oxygen Tension ◽

Arterial Oxygen ◽

Absolute Pressure ◽

Fetal Lamb ◽

Near Term

The ability of the pulmonary circulation of the fetal lamb to respond to a rise in oxygen tension was studied from 94 to 146 days of gestation. The unanesthetized ewe breathed room air at normal atmospheric pressure, followed by 100% oxygen at three atmospheres absolute pressure in a hyperbaric chamber. In eleven near-term lambs (132 to 146 days of gestation), fetal arterial oxygen tension (PaO2) increased from 25 +/- 1 to 55 +/- 6 Torr (mean +/- SE), which increased the proportion of right ventricular output distributed to the fetal lungs from 8 +/- 1 to 59 +/- 5%. In five very immature lambs (94 to 101 days of gestation), fetal PaO2 increased from 27 +/- 1 to 174 +/- 70 Torr, but the proportion of right ventricular output distributed to the lung did not change, 8 +/- 1 to 9 +/- 1%. In five of the near-term lambs, pulmonary blood flow was measured. It increased from 34 +/- 3 to 298 +/- 35 ml.kg fetal wt-1.min-1, an 8.8-fold increase. We conclude that the pulmonary circulation of the fetal lamb does not respond to an increase in oxygen tension before 101 days of gestation; however, near term an increase in oxygen tension alone can induce the entire increase in pulmonary blood flow that normally occurs after the onset of breathing at birth.

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