Average central aortic pressure in full-term neonate is_____ mm Hg?
Ans. a (75/50) (Ref. Nelson Paediatrics 18th/1856; OP Ghai 6th/393)Nelson pediatrics 18th/p. 1856 under heading Neonatal Circulation:# The average central aortic pressure in a term neonate is 75/50 mm Hg.THE NEONATAL CIRCULATION# At birth, the fetal circulation must immediately adapts to extrauterine life as gas exchange is transferred from the placenta to the lung.- After an initial slight fall in systemic blood pressure, a progressive rise occurs with increasing age.0- The heart rate slows as a result of a baroreceptor response to an increase in systemic vascular resistance when the placental circulation is eliminated.- The average central aortic pressure in a term neonate is 75/50 mm Hg.- The onset of ventilation, pulmonary vascular resistance is markedly decreased as a consequence of both active (PO2 related) and passive (mechanical related) pulmonary vasodilation.* The major decline in pulmonary resistance from the high fetal levels to the low "adult" levels in the human infant at sea level usually occurs within the 1st 2-3 days but may be prolonged for 7 days or more.* Over the 1st several weeks of life, pulmonary vascular resistance decreases even further, secondary to remodeling of the pulmonary vasculature, including thinning of the vascular smooth muscle and recruitment of new vessels.Significant differences between the neonatal circulation and that of older infants include:- right-to-left or left-to-right shunting may persist across the patent foramen ovale;- in the presence of cardiopulmonary disease, continued patency of the ductus arteriosus may allow left-to-right, right-to-left, or bidirectional shunting;- the neonatal pulmonary vasculature constricts more vigorously in response to hypoxemia, hypercapnia, and acidosis;- the wall thickness and muscle mass of the neonatal left and right ventricles are almost equal; and- newborn infants at rest have relatively high oxygen consumption, which is associated with relatively high cardiac output.# The newborn cardiac output is about 350 mL/kg/min.# CO falls in the 1st 2 months of life to about 150 mL/kg/min# Then more gradually to the normal adult cardiac output of about 75 mL/kg/min.# The foramen ovale is functionally closed by the 3rd mo of life.# Functional closure of the ductus arteriosus is usually complete by 10--15 hr in a normal neonate0# The normal ductus arteriosus differs morphologically from the adjoining aorta and pulmonary artery in that the ductus has a significant amount of circularly arranged smooth muscle in its medial layer.# During fetal life, patency of the ductus arteriosus appears to be maintained by the combined relaxant effects of low oxygen tension and endogenously produced prostaglandins, specifically prostaglandin E2# In a full-term neonate, orygen is the most important factor controlling ductal closure.0# 'When the PO2 of the blood passing through the ductus reaches about 50 mm Hg, the ductal wall constricts.
75/50
60/40
40/20
20/10
C.V.S.