AJP - Regulatory, Integrative and Comparative Physiology, Vol 247, Issue 4 626-R633, Copyright © 1984 by American Physiological Society
Cardiovascular responses to arterial and venous hemorrhage in neonatal swine
B. J. Buckley, N. Gootman, J. S. Nagelberg, P. G. Griswold and P. M. Gootman
The cardiovascular effects of graded arterial or venous hemorrhage were
evaluated in developing swine (less than or equal to 1 day, 2-5 days, 1 wk,
and 2 wk of age) anesthetized with halothane in 50% N2O-50% O2. Serial
5-ml/kg aliquots of arterial or venous blood were removed at 3- to 4-min
intervals to a cumulative total of 20 ml/kg. Tachycardia occurred in most
animals. Decreases in aortic pressure to arterial, but not to venous,
hemorrhage were age dependent. Renal, femoral, and carotid arterial flows
decreased with hemorrhage in all animals; the decreases in blood flow did
not differ among the three circulations and were not age dependent.
Increases in femoral resistance were obtained to both arterial and venous
hemorrhage only in the 2-wk-old group. As the degree of hemorrhage was
increased, aortic pressure, regional blood flow, and femoral resistance (2
wk olds) responses were larger in magnitude. Aortic pressure in piglets 1-5
days of age could not be restored to within 20% of the prehemorrhage level
at a smaller bleeding volume with arterial than with venous hemorrhage.
Pressor responses to norepinephrine (0.5 micrograms/kg) and to bilateral
common carotid occlusion were still present after 20-ml/kg hemorrhage.
These responses indicate the presence of a progressive maturation-related
compensation to the stress of arterial but not venous hemorrhage.
