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TAS Neonatal Medicine ✅ > Fluid, Electrolytes, Feeding, and Nutrition ✅ > Flashcards

Fluid, Electrolytes, Feeding, and Nutrition ✅ Flashcards

1
Q

What is the total body fluid in neonates distributed among?

A

3 major fluid spaces - plasma, interstitial, and cellular space

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2
Q

Is the proportion of fluid in each of the compartments the same in infants and adults?

A

No, very different

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3
Q

How does the extra cellular fluid expressed as a percentage of body weight differ at 26 weeks, term, and in the adult?

A

In 26 weeks, 50% of fluid is extracellular fluid. In term, around 35%, and in adults, around 20%.
Therefore, relatively less dry weight in younger.

Volume of intracellular fluid is the same.

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4
Q

What is the result of the differing proportion of fluids in each compartment in the neonate compared to an adult?

A

A different approach to fluid management is required

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5
Q

What % of the total body weight is water in the early fetal period?

A

95%

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6
Q

What % of the total body weight is water at term?

A

75%

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7
Q

What happens to the distribution of fluid throughout the compartments as the foetus grows?

A

The amount of fluid in the extracellular spaces decreases gradually, and there is a slow increase in intracellular fluid

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8
Q

Why is it important to consider the change in fluid distribution throughout the neonatal period?

A

It affects decision-making about fluid changes, especially in the sick preterm infant

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9
Q

What factors affect the neonatal fluid balance?

A
  • GFR
  • RDS
  • Transepidermal water loss (TEWL)
  • Complications of prematurity
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10
Q

How does the GFR in an extremely preterm infant compare to that of a term infant?

A

It is only around 1/4 of that of a term infant

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11
Q

What is the result of the GFR being lower in an extremely preterm infant compared to a term infant?

A

It makes them vulnerable for fluid overload and hyponatraemia, as well as dehydration and hypernatraemia

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12
Q

What else can increase the risk of hypernatraemia in an extremely preterm infant?

A

Their immature renin-angiotensin mechanism increases the risk following rapid correction of sodium

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13
Q

What happens to all babies in the immediate post-natal period, regarding their renal function?

A

They undergo a diuretic phase

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14
Q

What regulates the diuretic phase in the immediate post-natal period?

A

An increase in atrial natriuretic peptide

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15
Q

What does the diuretic phase in the immediate post-natal period lead to?

A

A physiological contraction of the extracellular volume

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16
Q

Describe the sodium balance in a neonate?

A

There is a negative sodium balance early on, followed by sodium retention in the kidney

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17
Q

What is a negative sodium balance early on followed by sodium retention in the kidney important for?

A

Growth

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18
Q

At what gestational age are premature infants able to maintain an adequate water balance over a wide range of fluid intake?

A

> 30 weeks

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19
Q

What can affect fluid homeostasis in extremely preterm infants (<30 weeks)?

A
  • Administration of fluid blouses
  • Infection
  • Hypotension
  • Mechanical ventilation
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20
Q

How does RDS affect fluid balance?

A

Infants with RDS have a delayed diuretic phase, and their extracellular volume is not decreased

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21
Q

What is the result of the extracellular volume of infants with RDS not being decreased due to the delayed diuretic phase?

A

It is important not to give extra fluids and sodium before the diuretic phase

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22
Q

Why is there a high transepidermal water loss (TEWL) in babies?

A

Due to their large surface area and thin, permeable, non-keratinised skin

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23
Q

How does the TEWL in infants of 25 weeks gestation compare to that of term infants?

A

It can be up to 15 times higher

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24
Q

What can reduce the TEWL in preterm infants?

A
  • Nursing inside an incubator with high humidity
  • Humidification of respiratory gases
  • Good skin care
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25
Q

How high is the humidity in an incubator?

A

Up to 80%

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26
Q

What neonatal complications can lead to hyponatraemia?

A
  • Pneumothorax
  • Intraventricular haemorrhage
  • Conditions requiring surgery
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27
Q

What might complications of prematurity lead to, regarding sodium?

A

Hyponatraemia

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28
Q

How can complications of prematurity lead to hyponatraemia?

A
  • Diminished capacity to excrete a free water load
  • Increased sodium loss in the urine
  • Iatrogenic fluid administration of hypotonic, low sodium solutions
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29
Q

Is true SIADH common in neonates?

A

No, probably rare

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30
Q

What are the fluid requirements of a term neonate at day 1?

A

Around 50ml/kg/day

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31
Q

What are the fluid requirements for a term neonate at day 7?

A

Around 150ml/kg/day

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32
Q

What are the fluid requirements of a preterm neonate at day 1?

A

60-70ml/kg/day

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33
Q

What are the fluid requirements of a preterm neonate at day 7?

A

Up to 175ml/kg/day

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34
Q

What are the energy requirements of a term infant?

A

100kcal/kg/day

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35
Q

What are the energy requirements of a preterm infant?

A

120kcal/kg/day

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36
Q

What are the energy requirements of an IUGR infant?

A

Up to 140kcal/day/kg

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37
Q

What fluids are given to infants in the first 2-3 days of life if IV fluids are required?

A

Solute-free dextrose solution

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38
Q

Why is a solute free dextrose solution used in the first 2-3 days of life?

A
  • Na/K-ATPase mechanism is affected during intensive care for sick babies
  • Infants have a limited ability to handle solute load in administered fluid
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39
Q

What is the Na/K-ATPase mechanism responsive for?

A

Maintaining sodium and potassium balance

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40
Q

Why do infants have a limited ability to handle solute load in administered fluid?

A

Due to renal impairment

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41
Q

What does serum sodium levels reflect?

A

Sodium and water balance

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42
Q

What is considered to be hypernatraemia?

A

> 145mmol/L

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43
Q

What is happening with regard to sodium and fluid in hypernatraemia?

A

There is an absolute or relative deficit of body water in relation to body sodium

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44
Q

What is considered to be hyponatraemia?

A

<135mmol/L

45
Q

What is happening with regard to sodium and water in hyponatraemia?

A

There is a relative or absolute excess of body water

46
Q

What needs to be clinically assessed when determining the cause of hypo or hypernatraemia?

A

Change in weight and clinical context

47
Q

What does weight gain in the first few postnatal days with normal serum sodium indicate?

A

Isotonic expansion of extracellular space and a positive sodium and water balance (at a time when it should be negative)

48
Q

What does hyponatraemia with weight loss or inadequate weight gain indicate?

A

Sodium depletion

49
Q

What is required when sodium depletion is suspected to be the cause of hyponatraemia?

A

Supplemental sodium

50
Q

How is hyponatraemia caused by fluid excess treated?

A
  • Fluid restriction

- Treatment of underlying cause

51
Q

What does hypernatraemia with weight loss suggest?

A

Dehydration

52
Q

What does hypernatraemia with weight gain suggest?

A

Sodium and water overload

53
Q

Where does most of the potassium in the body exist?

A

In the intracellular compartment

54
Q

Do blood levels of potassium reflect total body potassium?

A

No, not usually

55
Q

What maintains the high intracellular potassium concentration?

A

The Na/K-ATPase

56
Q

How does the Na/K-ATPase maintain the high intracellular potassium concentration?

A

By pumping sodium out and potassium into the cell

57
Q

What is potassium necessary for?

A

The electrical responsiveness of muscle cells, and the contractile to of cardiac, skeletal, and smooth muscles

58
Q

When must potassium rich fluids be avoided?

A

If there is oliguria or anuria due to renal compromise

59
Q

What is the daily sodium requirement of a term infant?

A

2.5-3.5mmol/kg

60
Q

What is the daily potassium requirement of a term infant?

A

2.5-3.5mmol/kg

61
Q

What is the daily chloride requirement of a term infant?

A

5mmol/kg

62
Q

What is the daily phosphorus requirement of a term infant?

A

1.0-1.5mmol/kg

63
Q

What is the daily calcium requirement of a term infant?

A

1.2-1.5mmol/kg

64
Q

What is the daily magnesium requirement of a term infant?

A

0.6mmol/kg

65
Q

What is the daily sodium requirement of a preterm infant?

A

3-4mmol/kg

66
Q

What is the daily potassium requirement of a preterm infant?

A

2-3mmol/kg

67
Q

What is the daily chloride requirement of a preterm infant?

A

1.5-4.5

68
Q

What is the daily phosphorus requirement of a preterm infant?

A

1.9-4.5mmol/kg

69
Q

What is the daily calcium requirement of a preterm infant?

A

3-5.5mmol/kg

70
Q

What is the daily magnesium requirement of a preterm infant?

A

0.3-0.6mmol/kg

71
Q

What is the normal weight loss in the first week in a healthy term infant?

A

About 5-7%

72
Q

Why do term infants normally loose 5-7% of their birth weight?

A
  • Physiologic contraction of extracellular water volume

- Catabolism secondary to low caloric intake

73
Q

When is the weight loss of a term infant most marked?

A

On day 2-3

74
Q

When should an infant regain their birth weight?

A

Within 2 weeks

75
Q

When might the initial weight loss in infants be more marked?

A

In breastfed infants

76
Q

What can weight loss in excess to 10% lead to?

A

Hypernatraemic dehydration

77
Q

How much weight does a baby gain in the first 6 months?

A

Average of around 30g/day

78
Q

When should an infant double their birth weight?

A

Around 4-5 months

79
Q

When should an infant treble their birth wight?

A

1 year of age

80
Q

What are the benefits of breast feeding to the baby?

A
  • Most suitable source of nutrition
  • Reduced risk of infection
  • May be protective in eczema
  • Beneficial effect on later ‘cardiovascular’ health
  • May improve later cognitive function
  • May protect against SIDS
81
Q

What infections does breastfeeding reduce the risk of?

A
  • Gastroenteritis
  • Otitis media
  • Probably severe lower respiratory tract infection requiring hospitalisation
82
Q

When might breastfeeding be protective in eczema?

A

In infants with a positive family history

83
Q

In what ways does breastfeeding have a beneficial effect on later cardiovascular health?

A

Improves plasma lipid profile, blood pressure, and risk of obesity

84
Q

What confounds the evidence that breastfeeding reduces the risk of SIDS?

A

May be through maternal education, socio-economic status, and birth weight

85
Q

What are the advantages of breastfeeding in a preterm infant?

A
  • Better gastrointestinal tolerance
  • Reduced incidence of necrotising enterocolitis (NEC) and systemic infection
  • Improved cognitive outcome
  • Lower BP, more favourable plasma lipid profile, and higher bone mass during childhood and adolescence
86
Q

What are the benefits of breastfeeding for the mother?

A
  • Better mother-infant bonding
  • Sense of personal achievement
  • More rapid weight loss
  • Readily available without any preparation
  • Easy to express and store
  • Delayed return to menses
  • Uterine involution through oxytocin
  • No cost
  • Some protection against osteoporosis, ovarian and breast cancer
87
Q

Why might a delayed return to menses be beneficial?

A

Increased time-interval to next child is important when alternative birth control is not available

88
Q

What happens to the breast in pregnancy?

A

There is a marked increase in the number of breast ducts

89
Q

What causes the increase in the number of breast ducts in pregnancy?

A

Response to progesterone, oestrogen, and placental lactometer

90
Q

When does secretion of prolactin start?

A

In the last trimester

91
Q

What triggers the secretion of colostrum?

A

Prolactin from the anterior pituitary causes glandular tissue to secrete small amounts of colostrum

92
Q

What controls milk flow after birth?

A

The let down reflex

93
Q

What mediates the let down reflex?

A
  • Afferent impulse from the baby rooting at the nipple

- Oxytocin secretion from the posterior pituitary

94
Q

How does oxytocin stimulate cause milk to be released?

A

Oxytocin squeezes milk into large ducts through smooth muscle fibre stimulation around alveoli

95
Q

What maintains milk production?

A
  • Prolactin secretion

- Effective suckling and emptying of breast milk

96
Q

What is the energy content of breast milk?

A

67kcal/100ml

97
Q

What are the main constituents of breast milk?

A
  • Fat (54%)
  • Carbohydrate (40%)
  • Protein (6%)
98
Q

Describe the protein content of breast milk, and how it differs from cows milk?

A
  • It has a relatively low amount of protein, but with a high whey:casein ratio of 0.7
  • It has twice as much lactalbumin as cows milk, but no lactoglobin
  • There are high levels of amino acids such as taurine, aspartic acid, glutamic acid, and asparagine
99
Q

What is a large amount of the nitrogen in breast milk derived from?

A

Non-protein sources

100
Q

How does the absorption of fat in breast milk compare to cows milk?

A

It is better

101
Q

Why is the absorption of fat better in breast milk compared to cows milk?

A

Due to smaller size of fat globules and lipase content

102
Q

How does the fat content of breast milk compare to cows milk?

A
  • Higher amount of unsaturated fatty acids
  • Higher amount of vitamins A, C, E, and nicotinic acid
  • Less of vitamins B and K
103
Q

Is the renal solute load high or low in cows milk?

A

Low

104
Q

How do the calcium and phosphate levels in breast milk compare to cows milk?

A

They are lower, but better absorbed

105
Q

What are the maternal contraindications to breastfeeding?

A
  • Severe acute illness, e.g. sepsis
  • Breast abscess
  • Chemotherapy
  • Some mental health drugs, e.g. lithium
  • Active TB
  • HIV
106
Q

What are the neonatal contraindications to breastfeeding?

A
  • Metabolic conditions such as galactosaemia, phenylketonuria
  • Lactose intolerance
107
Q

In what condition might breastfeeding be difficult to establish?

A

Severe cleft lip/palate

108
Q

What is the alternative option to breastfeeding?

A

Artificial, or formula feeding

109
Q

What are the key differences between breastfeeding and formula feeding?

A
  • High casein protein content and relatively low whey:casein ratio
  • Low lactose content
  • No immunological benefits
  • Higher calcium, phosphate, and iron content, but less absorption and bioavailability

TAS Neonatal Medicine ✅ (35 decks)

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