DEPRESSED RESPONSIVENESS TO VASOCONSTRICTOR AND DILATOR AGENTS AND BAROREFLEX SENSITIVITY IN CONSCIOUS, NEWBORN LAMBS

被引:40
作者
MANDERS, WT
PAGANI, M
VATNER, SF
机构
[1] NEW ENGLAND REG PRIMATE RES CTR,1 PINE HILL DR,SOUTHBORO,MA 01772
[2] HARVARD UNIV,CHILDRENS HOSP,MED CTR,SCH MED,DEPT CARDIOL,BOSTON,MA 02115
[3] HARVARD UNIV,SCH MED,DEPT MED,BOSTON,MA 02115
[4] PETER BENT BRIGHAM HOSP,DEPT MED,BOSTON,MA 02115
关键词
D O I
10.1161/01.CIR.60.4.945
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
The effects of vasoconstrictors and vasodilators were compared in conscious, newborn lambs and adult sheep instrumented with electromagnetic flow probes on the ascending aorta and catheters in the thoracic aorta. Methoxamine, angiotensin II, norepinephrine, nitroglycerin and isoproterenol were administered intravenously to evaluate their effects on arterial pressure, cardiac output and systemic vascular resistance (SVR). The difference in response between adults and newborns was most apparent with methoxamine. Methoxamine, 400 μg/kg, i.v., which increased mean arterial pressure by 57 ± 6% and SVR by 278 ± 27% in newborn lambs, caused greater increases (p<0.01) of 81 ± 8% and 1418 ± 141%, respectively, in the adults. Responses also differed significantly between newborn and adult animals to norepinephrine, angiontensin II, nitroglycerin and isoproterenol. In a second group of animals in which smaller amounts of methoxamine and isoproterenol were injected directly into the terminal aorta, changes in terminal aortic flow and resistance were examined. Again, both vasoconstrictor and vasodilator responses were more marked in adults than in newborns. Finally, the sensitivity of the arterial baroreceptor reflex was evaluated by comparing the regression of pulse interval (PI) on systolic arterial pressure (SAP) after an intravenous dose of methoxamine in conscious, adult and newborn animals. The PI/SAP slopes in adult sheep, 45.4 ± 3.5 msec/mm Hg, were significantly greater (p<0.01) than in newborn lambs, 11.7 ± 2.2 msec/mm Hg.
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收藏
页码:945 / 955
页数:11
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