Fetal-neonatal physiology Flashcards
If placenta is poorly functioning =
Intrauterine growth restriction
Chronic hypoxia
Newborns should be
Warm
Sweet
Pink
Newborns should not be
Hypothermic
Hypoglycemic
Cyanosed
ABCDEFG
Airway
Breathing
Circulation
dont ever forget Glucose
Size of newborn airway
2.5-3.5 cm
The newborns airway is easily obstructed with
Fluid, blood, meconium
Gas exchange can only take place at what stage of lung development?
Terminal sac stage
Alveolar phase of lung development occurs at
30 weeks
Surfactant is produced at
32 weeks
Ex of congenital lung abnormalities =
Diaphragmatic hernia
Pulmonary hypoplasia
Diaphragmatic hernia =
Diaphragm failed to develop. Baby is born with bowel on 1 side of chest so lung cannot grow and expand
Pulmonary hypoplasia
Incomplete development of the lungs, resulting an abnormally low number or size of bronchopulmonary segments or alveoli
What do lungs need in utero to form?
Fluid matrix - formed from kidneys
Why might the fetus not have a fluid matrix in lungs?
Chronic leaking No kidneys (Potters)
Surfacts =
Phospholipid, reduces surface tension in alveoli
Babies born before surfactant production have
Respiratory distress syndrome
Why are some babies surfactant deficient?
- Premature
- Congenital abnormalities
- Myconium aspiration
- Hypoxia - lactiacidosis
- Infection
Why does meconium aspiration reduce surfactant?
Blocks airway, neutralises surfactant
Respiratory distress syndrome may lead to a
Pneumothorax
Respiratory distress syndrome on CXR =
Ground glass appearance
Poorly expanded lungs
Air bronchograms
Small lung volume
Ground glass appearance due to =
Fluid, consolidation, alveoli not fully expanded
Air bronchograms =
Dark bronchi, due to alveoli around it being white
Number of umbilical arteries
2
Number of umbilical veins
1
Umbilical arteries carry
Deoxygenated blood away from fetus
Umbilical veins carry
Oxygenated blood towards fetus
Adaptations of fetal circulation before birth:
- Ductus venosus
- Foramen ovale
- Ductus arteriosus
- Increased vascular resistance in lungs
Ductus venosus
Shunts blood from umbilical vein to IVC
Ducutus arteriosus
Shunts blood from pulmonary artery to aorta
Foramen ovale becomes what after birth?
Fossa ovalis
Why do lungs have a high resistance before birth?
Hypoxic pulmonary vasoconstriction
What closes first after birth?
Foramen ovale
What closes last after birth?
Ductus venosus
Why/how does the ductus arteriosus close?
High O2, vasoconstriction
What can be used to diagnose septal defects?
Echocardiogram
What may cause the circulation to fail to adapt?
Lungs:
Surfactant deficiency
Congenital pneumonia
Meconium aspiration
Cardiac:
Duct dependent circulation
Duct dependant relies on what?
Ductus arteriosus
Duct dependent circulation cna be subdivided into:
- DD systemic
- DD pulmonary
- Both
Duct dependent systemic circulation can be due to:
- Coarctation of the aorta
- Critical aortic stenosis
- Hypoplastic left heart syndrome
Duct dependent pulmonary circulation can be due to:
Pulmonary artresia
Ciritical pulmonary stenosis
Tricuspid atresia
Tetralogy of Fallot
Tetralogy of Fallot =
- Pulmonary artery stenosis
- Right ventricular hypertrophy
- Ventricular septal defect
- Aorta overlying VSD
What is different about the VSD in the Tetralogy of Fallot?
Right to left shunting (due to high pulmonary pressures)
Cause of duct dependent systemic and pulmonary circulations
Transposition of the great arteries
Aorta on right, Pulmonary artery on left
Transposition of the great vessels leads to
2 separate loops
Entirely reliant on ductus for circulation
What does persistent pulmonary hypertension cause?
Patent ductus arteriosus
How to treat persistent pulmonary hypertension
BP in lungs down, BP in body higher
- Pulmonary vasodilators (NO)
- Ventilate
- Give surfactant
What makes blood cells in fetus?
Yolk sac –> liver –> spleen –> bone marrow
Fetal glucose is derived from
Mother (80% maternal level)
Why might children of uncontrolled diabetic cause hypoglycemic baby?
Used to high sugars - high insulin
Babies at risk of hypoglycemia =
- B blocker mother
- Septic
- Asphyxiated
- High Hb (polycytaemia)
- premature
- Diabetic mum
- Inherited metabolic disorder
- Growth restriction
Weight of children =
Lose in week one (no more than 7%)
Should gain back by week 2
