Abstract
Piglets, 3.3±0.3 (Gr I) and 15.6±0.4 (Gr II) days of age, were anesthetized, ventilated and paralyzed; the ductus arteriosus was ligated. ECG, aortic (AO) and LV pressures, LV dP/dt max, and phasic pulmonary (cardiac output, CO) and superior mesenteric (Mes) arterial flows were continuously recorded; resistance (R) was calculated. Sequential 10 min infusions of ISO (0.05, 0.1, 0.2 mcg/kg/min) were given during normoxemia (NO, PO2 99±3 mm Hg) and repeated during moderate (M) H (PO2 58±1 mm Hg) in 17 piglets or severe (S) H (PO2 38±1 mm Hg) in 13 piglets. In 18 age-matched controls saline was infused instead of ISO and no significant changes were observed. Mean % changes ± SE to 0.2 mcg/kg/min ISO are presented. In Gr I MH diminished increases in LV dP/dt max (54±10 vs 19±7, p<0.01), CO (22±6 vs 9±6, p<0.02) and HR (28±5 vs 14±3, p<0.02). In contrast MH augmented increases in LV dP/dt max (51±8 vs 68±9, p<0.02) and did not alter dose-dependent increases in HR (29±7) and CO (32±12) in Gr II. In Gr I, SH attenuated increases in HR (34±5 vs 13±3, p<0.01) and LV dP/dt max (43±11 vs 3±6, p<0.01) but not in CO. In Gr II, SH reduced increases in LV dP/dt max (38±9 vs 10±8) in all animals and in HR ( 36±11 vs 10±3) in 6 of 7 animals. ISO had no significant effect on AO pressure during NO, MH or SH in Gr I and II. MesR was not significantly affected by ISO during NO but decreased (15±4, p<0.02) during MH in Gr I. However, in Gr II MesR decreased (15±3, p<0.01) during NO, but increased (23±7, p<0.02) during MH. During SH, ISO had variable effects on MesR in Gr I and II. The results indicate that cardiovascular responses to ISO in newborn swine are signifiantly affected in magnitude and direction by arterial PO2 level and postnatal age.
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Nuclei, D., Peterson, B., Bucklay, B. et al. EFFECTS OF HYPOXEMIA (H) ON CARDIOVASCULAR RESPONSES TO ISOPROTERENOL (ISO) IN NEONATAL SWINE. Pediatr Res 18 (Suppl 4), 128 (1984). https://doi.org/10.1203/00006450-198404001-00212
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DOI: https://doi.org/10.1203/00006450-198404001-00212