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Year 3 Clinical > Adaptation at Birth > Flashcards

Adaptation at Birth Flashcards

1
Q

Functions of the placenta?

A

Foetal homeostasis

Gas exchange - placenta acts as the foetal lung

Nutrient transport to the foetus

Waste product transport from the foetus

Acid-base balance

Hormone production

Transport of IgG (mainly in the 3rd trimester, closer to the time of delivery)

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2
Q

Hormones produced by the placenta?

A

Insulin-like Growth Factor (IGF) 1 &2 - allow foetal growth

Placental lactogen

Oxytocin (mainly produced by the maternal hypothalamus but also by the placenta)

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3
Q

3 shunts of the foetal circulation?

A
  1. Ductus venosus (from the umbilical vein to the IVC)
  2. Foramen ovale (between the right and left sides of the heart)
  3. Ductus arteriosus (between the pulmonary artery and the aorta)
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4
Q

Why does the placenta act as the foetal lung, rather than the baby’s lungs themselves?

A

Lungs are growing and developing and, during pregnancy, are fluid-filled

The pulmonary vascular resistance is very high, so only 7% of the output proceeds via the lungs; this provides a blood supply for the developing lungs

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5
Q

Oxygenation of the foetal circulation?

A

Umbilical vein carries oxygenated blood (80% oxygenation)

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6
Q

What preparations for birth are made during the 3rd trimester?

A

Surfactant production by type II pneumocytes

Glycogen accumulation, in liver, muscle and the heart

Accumulation of brown fat (unique to the neonate) between the scapulae and around the internal organs

Accumulation of s/c fat (breakdown is essential for the starving neonate)

Swallowing of amniotic fluid (allows development of the lungs and, to some degree, the GI organs)

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7
Q

What preparations for birth are made during labour and delivery?

A

At the onset of labour, catecholamines / cortisol increase, to prepare for gluconeogenesis and thermogenesis

Synthesis of lung fluid stops

Vaginal delivery is thought to squeeze the lungs and help the lungs to switch from transepithelial Cl- production to Na+ reabsorption, allowing the lung fluid production to cease

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8
Q

Within the first few seconds of life, what changes occur?

A

The baby is born blue; they begin to breathe and cry, gradually turning pink (this takes 5-10 minutes, usually turning pink from the centre to the periphery)

The cord is cut; in a healthy, term baby, cutting of the cord is delayed by ~1 minute

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9
Q

Why is crying in the first few seconds important?

A

Crying floods the lungs with +ve pressure, opening them up and pushing any remaining lung fluid into the lymphatics

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10
Q

Circulatory transitions that occur?

A
  1. Pulmonary vascular resistance drops and systemic vascular resistance rises
  2. Oxygen tension rises
  3. Circulating PG levels drop (closing the ductus arteriosus)
  4. Ductus arteriosus constricts, driven by 3 factors:
    • Rising pO2
    • Decreased blood flow
    • Decreased PGs
  5. Foramen ovale closes
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11
Q

What happens to the different foetal shunts?

A

Foramen ovale:
• Closes (normal)
• Persists as the PFO

Ductus arteriosus:
• Becomes the ligamentum arteriosus (normal)
• Persistent ductus arteriosus

Ductus venosus:
• Becomes the ligamentum teres

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12
Q

Major risk factor for persistent ductus arteriosus?

A

Preterm baby

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13
Q

Situations where a failure of cardiorespiratory adaptation may occur?

A

Preterm babies

Babies that pass meconium before birth

Babies that get cold during delivery

Babies with infection

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14
Q

What is Persistent Pulmonary Hypertension of the Newborn (PPHN)?

A

Persistence of the foetal circulation, characterised by marked pulmonary hypertension, leading to hypoxaemia secondary to right-to-left shunting of blood (via the foramen ovale and ductus arteriosus)

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15
Q

Ix for PPHN?

A

Significant difference between the pre- and post-ductal oxygenation (at least 5-10%); the higher the gap, the worse the pulmonary hypertension

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16
Q

Mx of PPHN?

A

Ventilation

O2

Nitric oxide (causes vasodilatation)

Sedation

Inotropes

Extra-Corporeal Life Support (ECLS) - heart-lung bypass

17
Q

What is Transient Tachypnoea of the Newborn (TTN)?

A

Most common cause of respiratory distress of the newborn; occurs due to fluid that remains the lungs

18
Q

Important bodily processes during the first few hours as a newborn?

A
  1. Thermogenesis
  2. Glucose homeostasis
  3. Nutrition
19
Q

Why are babies vulnerable to heat loss?

A

Large surface area : volume ratio

Wet when born

They cannot shiver

NOTE - newborn babies need help maintaining their temperature

20
Q

4 methods by which heat loss occurs?

A
  1. Evaporation
  2. Radiation
  3. Conduction
  4. Convection
21
Q

Main method of heat production in newborns?

A

Non-shivering thermogenesis - heat is produced by breakdown of stored brown adipose tissue, in response to catecholamines

It is not efficient in the first 12 hours of life

22
Q

Other methods of newborns retaining heat?

A

Peripheral vasoconstriction

23
Q

Causes of hypothermia in an SGA / preterm baby?

A

Low stores of brown fat

Little s/c fat

Larger SA : V ratio

24
Q

Why is hypothermia in a newborn so problematic?

A

Predisposes to other problems, e.g: hypoglycaemia

25
Q

Why is glucose homeostasis so important in the newborn?

A

Interruption of glucose supply from the placenta

Very little oral intake of milk (in the first 24 hrs, the baby takes in only 5mls of colostrum, so the glucose must come from elsewhere)

26
Q

Adaptations in the newborn that allow glucose homeostasis?

A

Drop in insulin and increase in glycogen

Mobilisation of hepatic glycogen stores for gluconeogenesis

Ability to use ketones as brain fuel

27
Q

Why does hypoglycaemia occur in a newborn?

A

Increased energy demands:
• Unwell baby
• Hypothermia

Low glycogen stores:
• SGA
• Preterm

Inappropriate insulin / glycogen ratio:
• Maternal diabetes
• Hyperinsulinism

Drugs, e.g: maternal use of labetalol (β-blocker)

28
Q

Methods of avoiding / treating hypoglycaemia?

A

Identify at risk babies

Feed effectively

Keep warm (hypothermia causes/worsens hypoglycaemia)

Monitor

29
Q

Explain the physiology of breastfeeding

A

Rooting and suck reflex allows the baby to suckle; this sensory input triggers the hypothalamus to stimulate the:
• Posterior pituitary - releases oxytocin, allowing milk ejection (let-down reflex)
• Anterior pituitary - releases prolactin, allowing milk production

30
Q

Types of breastmilk?

A

The composition of breastmilk changes:
• Colostrum
• Foremilk and hindmilk

31
Q

Weight changes that occur after birth?

A

Babies often lose weight (up to 10% weight loss) in the first 7-10 days of life; if they lose more, it may be significant

Calculate the % weight loss

32
Q

Haematological changes that occur at birth?

A

Foetal Hb becomes disadvantageous at birth

Haematopoiesis moves to the bone marrow

Adult Hb is synthesised

33
Q

Why does physiological anaemia occur?

A

Adult Hb is synthesis more slowly than foetal Hb is broken down; nadir is at 8-10 weeks

34
Q

Why does physiological jaundice occur in the neonate?

A
  1. Breakdown of foetal Hb
  2. Conjugating pathways are immature
  3. Rise in circulating unconjugated bilirubin (generally nor harmful, unless the levels are very high)

NOTE - physiological jaundice is not harmful and the liver eventually catches up

35
Q

When might neonatal jaundice be pathological?

A

If it occurs <24 hours (early)

OR

If it is prolonged:
• Term >14 days
• Preterm >21 days

36
Q

What type of jaundice do neonates develop?

A

Almost always unconjugated hyperbilirubinaemia (as the cause is almost always pre-hepatic)

Conjugated hyperbilirubinaemia is more common in adults and, in neonates, really only occurs with biliary atresia

37
Q

When are jaundices babies treated?

A

ADD IMAGE

1st line is normally phototherapy, however this depends on the total bilirubin levels

2nd is exchange transfusion

NOTE - cannot assume that the baby has unconjugated hyperbilirubinaemia; it is important to check their history (pale stools and dark urine indicate conjugated hyperbilirubinaemia) and blood tests

38
Q

Which babies are at risk of a failure to adapt?

A 
Risk factors for adaptation problems:
• Hypoxia / asphyxia during delivery
• Part. small or large babies
• Premature babies 
• Some maternal illness and medications
• Ill babies (sepsis, congenital anomalies)

Year 3 Clinical (100 decks)

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