Term
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Definition
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Term
| What is are the changes that happen shortly after birth in transition from fetal to adult circulation? |
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Definition
PDA closure --> ligamentum arteriosum
DV closure --> ligamentum teres
PFO closure due to increased pressures in LA |
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Term
| What function does the placenta serve in fetal circulation? |
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Definition
respiratory and metabolic bc most of blood bypasses lungs
-active transport of nutrients
-diffusion of oxygen and carbon dioxide |
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Term
| How does fetal hemoglobin differ from adult hemoglobin? |
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Definition
-higher affinity for oxygen
-oxygen dissociate curve more suited to function at the low oxygen tension of the fetus
-normal PaO2 is 30-40 with a corresponding SaO2 >80% |
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Term
| Why is it necessary for fetal hemoglobin to have higher affinity for oxygen? |
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Definition
| Due to the mixing of oxygenated blood leaving the placenta and the deoxygenated blood returning to the placenta, there is lower oxygen tension in the intervillous space than arterial blood. As a result, fetal hemoglobin must have higher affinity than maternal hemoglobin to bind oxygen in this environment |
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Term
| How is lung fluid produced and at what rate? |
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Definition
| -Chloride pump on pulmonary endothelium faciilates production of lung fluid at rate of 4-6cc/kg/hr |
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Term
| Why is pulmonary vascular resistance higher than systemic vascular resistance in fetal circulation? |
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Definition
| -developing lungs are filled with fluid that constricts pulmonary vessels |
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Term
| Describe the blood flow across the ductus venosus, foramen ovale, and PDA in fetal circulatoin |
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Definition
Ductus venosus: shunts blood directly from placenta to IVC
Foramen ovale: oxygenated blood flows from RA -->LV
Ductus arteriosus: blood flows from PA--> aorta (R-L shunt) |
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Term
| What changes does the fetus undergo to prepare for delivery? |
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Definition
2-3 days prior to delivery:
-decrease in lung fluid production
-chloride pump is replaced by sodium pump
-Na pump transports Na from the alveolar space to the intersitium. Water follows
-2/3 of lung fluid is removed this way
-last 1/3 removed during first/second breath |
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Term
| Why do c-section babies huff and puff after birth? |
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Definition
| scheduled c-section babies might not have undergone the changes in preparation for delivery. |
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Term
| What stimulates a neonate's first breath? |
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Definition
1. elastic recoil (lung cavity squished during birth recoils and forces baby to gasp)
2. internal stimulation (hypoxemia, acidosis, hypercarbia)
3. external stimulation |
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Term
| What causes the drop in PVR after birth? |
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Definition
-physical expansion of the lungs mechanically lowers PVR
-increase in pulmonary blood flow causes shearing of the endothelium --> release of NO and prostacyclins
-NO and prostacyclins vasodilated PBV decreasing PVR
-increase oxygen tension from expansion of lungs and increased blood flow
-oxygen is a potent vasodilator in the lungs |
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Term
| How significant is the drop in PVR after birth? |
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Definition
| PVR drops by 75%; Pulm blood flow increases 450% |
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Term
| Why does systemic vasuclar resistance increase after birth? |
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Definition
-umbilical cord is clamped
-low resistance vascular bed is d/c and causing SVR to increase dramatically
-adrenal gland is dumping epinephrine, norepinephrine |
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Term
| What causes the ductus arteriosus close? |
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Definition
-increased oxygen ==> constrictor of the ductus
-prostalglandin E2 and NO levels drop (vasodilators) |
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Term
| Why is fetal distress dangerous for babies? |
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Definition
-fetal distress can causes baby to pass meconium inutero and then ingest it when gasping for breath.
-inhaling meconium can lead to chemical pneumonitis with respiatory distress |
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Term
| Why is indomethacin used? |
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Definition
| -NSAID that can be given to babies with PDA and asymptomatic??? |
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