Abstract
Extract: Cardiac output, renal blood flow, and intrinsic renal vasuclar 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 litres/min/m2, the mean renal blood flow increased from 0.043 to 0.76 litters/min/m2, and intrinsic renal vasuclar resistance dropped from 1,605 to 133 mm Hg/liter/min/m2. 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 outputs as well as decrease in renal vascular resistance. By 6 weeks of age, cardiac output was at adult levels. Since in the adult pig the kindney 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.
Speculation: In 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 I of life is due to steadily decreasing renal vascular resistence. 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.
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Gruskin, A., Edelmann, C. & Yuan, S. Maturational Changes in Renal Blood Flow in Piglets. Pediatr Res 4, 7–13 (1970). https://doi.org/10.1203/00006450-197001000-00001
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DOI: https://doi.org/10.1203/00006450-197001000-00001
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