Pulmonary blood flow and vascular resistance in immature foetal lambs

Cassin, S.; Dawes, G. S.; Roß, Bernhard

doi:10.1113/jphysiol.1964.sp007362

Cited by 103 publications

(40 citation statements)

References 9 publications

(5 reference statements)

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“…The placenta receives a major portion of the cardiac output while both the fetal lung and kidney [29] receive a relatively small proportion. A higher rate of blood flow to the lungs toward the end of gestation is prevented by a rise in pulmonary vascular resistance [6]. Measurements of renal vascular resistance in near-term fetal lambs, as in piglets, are reported as being high [31].…”

Section: Fetal and Neonatal Changes In Rbf And Pulmonary Blood Flowmentioning

confidence: 96%

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Maturational Changes in Renal Blood Flow in Piglets

1970

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ExtractCardiac output, renal blood flow, and intrinsic renal vascular resistance were measured in piglets ranging in age from 6 h to 45 days. During this period of time the mean cardiac output increased from 0.9 to 6.5 liters/min/m . These data demonstrate that the large increase in renal blood flow in the pig during the first 6 weeks of life was due to both an increase in cardiac output as well as a decrease in renal vascular resistance. By 6 weeks of age, cardiac output was at adult levels. Since in the adult pig the kidney receives 20 % of the cardiac output, increases in renal blood flow beyond 6 weeks of age must result from further decreases in renal vascular resistance. SpeculationIn the human infant, cardiac index is comparable to values observed in the adult. It appears, therefore, that the entire increase in renal blood flow observed during year 1 of life is due to steadily decreasing renal vascular resistance. Since glomerular filtration rate is modified by the relative resistances in the glomerular afferent and efferent arterioles, the parallel increases in filtration rate during infancy may be related to the same mechanism.Introduction mates renal plasma flow by not more than 30-40%. Rates of flow reach mature levels (1,200 ml/min/1.73 Numerous studies have shown that renal blood flow m

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Section: Fetal and Neonatal Changes In Rbf And Pulmonary Blood Flowmentioning

confidence: 96%

“…The CPAH increases five to six times during year 1 of life [2][3][4]6]. CALCAGNO and RUBIN [4] found that renal extraction of PAH in the young infant may be as low as 50%, suggesting that clearance of PAH markedly underestimates true renal plasma flow or the value of renal blood flow calculated from it.…”

Section: Age-related Changes In Rbf In Human Infantsmentioning

confidence: 99%

Maturational Changes in Renal Blood Flow in Piglets

1970

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“…The potential role far a-adrenergic constriction in the control of the pulmonary vasculature is suggested by observations of aadrenergic pulmonary vasoconstriction in a variety of experimental models (3,4,12,16,27). Furthermore, a-adrenergic pulmonary vasoconstriction in the neonatal lamb may be altered by hypoxia (20); circulating 1-norepinephrine levels are elevated markedly in stressed human neonates (18,24) and a-adrenergic blockade may be useful in treating neonatal pulmonary hypertension (1 1, 17).…”

Section: Discussionmentioning

confidence: 99%

“…There is evidence which suggests that a-adrenergic constriction may be involved in the control of the neonatal pulmonary circulation (4,14). Tolazoline, an a-adrenergic antagonist, has been used successfully to manage some babies with persistent pulmonary vasoconstriction (1 1, 17) although the therapeutic benefit of this drug also could be related to its histaminergic effects (10).…”

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confidence: 99%

A Comparison of the Sensitivities of Neonatal Ovine Pulmonary and Femoral Arteries to l-Norepinephrine Stimulation

Green

Leffler

1984

Pediatr Res

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“…There are several reasons why the longitudinal distribution of vascular resistance in the lung is likely to be different in the younger animal. The high pulmonary vascular resistance in the fetus (8,9) falls dramatically at birth (10, 11) but does not reach the low adult value until 3-6 months of age (12). Vascular resistance in the lung is high in early life partly due to a higher basal vasomotor tone (1 3) and in part due to differences in the morphology of the pulmonary vasculature (14).…”

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confidence: 99%

Micropuncture Measurement of Lung Microvascular Pressure Profile in 3- to 4-Week-Old Rabbits

1986

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ABSTRACT. We have reported the longitudinal distribution of vascular resistance in the three segments (arteries, microvessels, and veins) of the pulmonary circulation of adult rabbits (J Appl Physiol 60:539-545, 1986). To determine the longitudinal distribution of vascular resistance in lungs of younger animals, we measured microvascular Dressures in the sub~leural microcirculation in nine isolated blood perfused lungs of 3-to 4-wk-old rabbits. We used micropipettes and the servonull pressure measuring system to directly measure pressures in 20-50 pm diameter subpleural arterioles and veuules. We also measured pulmonary arterial and left atrial pressures and lung blood flow. To determine the influence of vascular tone on segmental vascular resistance, in four lungs we measured microvascular pressures both before and after paralyzing the vasculature with papaverine. We found that 51% of the total pressure drop in the pulmonary circulation was in arteries, 24.5% in microvessels, and 24.5% in veins. Vascular tone contributed minimally to baseline arterial resistance. The greater arterial and venous resistance in lungs of 3-to 4-wk-old rabbits as compared to that in adult rabbits is probably due to differences in vessel geometry. (Pediatr Res 20: 1107-11 11, 1986) Various methods have been used to determine the contribution of the three longitudinal segments of the pulmonary vasculature, i.e. the pulmonary arteries, microvessels, and veins to the total vascular resistance in the lung (1-4). Recently, with the development cf the technique of lung micropuncture, it has been possible to measure directly microvascular pressures in the subpleural microcirculation. Using this method, in the isolated dog lung, Bhattacharya and coworkers (5, 6) found that the major site of resistance to blood flow was the middle segment, i.e. microvessels <20 Fm in diameter. Using the same technique in the adult rabbit lung, we found that -60% of the total arteriovenous pressure drop occurs in vessels <20 pm in diameter, -33% occurs in arteries and only -7% occurs in veins (7). In the adult rabbits we had eliminated vascular smooth muscle tone in the lungs by paralyzing the vessels with papaverine.All the estimates of segmental vascular resistance in the lungs have been in lungs from adult animals. There are several reasons why the longitudinal distribution of vascular resistance in the lung is likely to be different in the younger animal. The high pulmonary vascular resistance in the fetus (8,9) falls dramatically at birth (10, 11) but does not reach the low adult value until 3-6 months of age (12). Vascular resistance in the lung is high in early life partly due to a higher basal vasomotor tone (1 3) and in part due to differences in the morphology of the pulmonary vasculature (14).In this study, using an isolated blood perfused lung preparation and the technique of lung micropuncture, we describe the distribution of vascular resistance in the pulmonary arteries, microvessels and veins in 3-to 4-wk old rabbits. METHODS Isolated lung pr...

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Pulmonary blood flow and vascular resistance in immature foetal lambs

Cited by 103 publications

References 9 publications

Maturational Changes in Renal Blood Flow in Piglets

Maturational Changes in Renal Blood Flow in Piglets

A Comparison of the Sensitivities of Neonatal Ovine Pulmonary and Femoral Arteries to l-Norepinephrine Stimulation

Micropuncture Measurement of Lung Microvascular Pressure Profile in 3- to 4-Week-Old Rabbits

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