The Effect of an Increase in Systemic Arterial Pressure in the Newborn with Right Ventricular Hypertension

Abstract

ABSTRACT. To evaluate the effect of an elevation in systemic arterial pressure upon pulmonary blood flow and arterial oxygenation during right ventricular hypertension (RVH), we acutely studied 13 1-d-old piglets. Catheters were positioned in the pulmonary artery, both atria, and the aorta for hemodynamic measurements. An electromagnetic probe was positioned in the main pulmonary artery for pulmonary blood flow measurement. Systemic and regional blood flow were measured with the radiolabeled microsphere technique. A balloon-mounted catheter was advanced in the aorta and maintained at the lower thoracic level. After induction of RVH (pulmonary artery banding), a significant decrease in arterial 0 2 pressure from 54.4 f 1.6 to 10.6 2 0.4 kPa (p < 0.01), a 30% reduction in systemic arterial pressure, and a 44% decrease in pulmonary blood flow were observed. During RVH, partial inflation of the aortic balloon to restore the systemic arterial pressure to its initial value led to an increase in arterial O2 pressure to 23.5 2 3.1 kPa ( p < 0.01). Full inflation of the balloon further increased the arterial O2 pressure to 32.6 f 2.9 kPa ( p < 0.01). Aortic balloon inflation increased pulmonary blood flow in 11 and systemic O2 delivery in nine of the 13 animals. RVH was associated with a significant increase in cerebral and right ventricular myocardial free-wall blood flow and a decrease in renal and bowel blood flow and O2 delivery (p < 0.01). Aortic balloon inflation during RVH did not change either the cerebral or myocardial free-wall blood flow, but further significantly decreased renal and bowel blood flow and O2 delivery. In conclusion, an elevation in systemic arterial pressure significantly reduces foramen ovale shunt and increases pulmonary blood flow and systemic O2 delivery in the newborn pig with RVH. This finding may prove useful in the clinical management of hypoxemic infants with persistent pulmonary hypertension syndrome. (Pediatr Res 28: 603-608, 1990 PPHN, persistent pulmonary hypertension syndrome Pao2, arterial O2 pressureIn the newborn pig, we have previously shown that RVH is associated with a significant decrease in PSA and cardiac output (1,2). The factors responsible for the reduction in cardiac output during RVH are presently unclear, but previously reported data suggest that the reduction is related to the changes in PSA (3-6). Meadow et al. (3)reported that after group B streptococcusinduced pulmonary hypertension in the piglet, a significant increase in Qp can be achieved by elevating the PSA Although not evaluated in their experimental animals, Meadow et al. also suggested that a selective elevation of the PsA during pulmonary hypertension could also impede right to left shunt at the foramen ovale and thus improve oxygenation (3). Furthermore, in adult animals with RVH and decreased Qp, an elevation in PSA increases cardiac output (4-6).In infants, the PPHN syndromeis associated with hypoxemia related not only to the decreased Qp, but also to the magnitude of the right to left shunt across ...

Pulmonary vasodilator effects of norepinephrine during the development of chronic pulmonary hypertension in neonatal lambs

“…14 In newborn piglets with right ventricular hypertension, an elevation in systemic arterial pressure reduced right to left foramen ovale shunt and increased pulmonary blood flow and systemic oxygen delivery. 17 Our results are consistent with these studies, suggesting that the norepinephrine-induced raise in AoP may be associated with increased pulmonary blood flow. A pulmonary vasodilator response to norepinephrine was observed after acute hypoxia in isolated perfused cat lung, 18 and in isolated intra-pulmonary arteries of neonatal and adult pigs.…”