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TAS Emergencies and Critical Care ✅ > Dehydration and Fluid Management ✅ > Flashcards

Dehydration and Fluid Management ✅ Flashcards

1
Q

How does the total body fluid compare in children to adults?

A

It is higher in children

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2
Q

What % of the body is made up of water at birth?

A

80%

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3
Q

What % of the body is made up of water by adulthood?

A

55-60%

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4
Q

Where is water distributed throughout the body?

A
  • Intracellular space

- Extracellular space

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5
Q

What proportion of water is distributed in the intracellular space?

A

2/3

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6
Q

What proportion of water is distributed in the extracellular space?

A

1/3

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7
Q

Where is water distributed within the extracellular space?

A
  • Interstitial

- Intravascular

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8
Q

What proportion of extracellular water is interstitial?

A

75%

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9
Q

What proportion of extracellular water is extracellular?

A

25%

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10
Q

What does the distribution of water between the intracellular and extracellular spaces depend on?

A

The pressure and osmotic gradients between them

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11
Q

What is dehydration?

A

Loss of water and electrolytes

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12
Q

What might cause children to become dehydrated?

A
  • Reduced oral fluid intake
  • Additional fluid losses
  • Increased insensible losses
  • Loss of normal fluid retaining mechanisms
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13
Q

What might cause reduced oral fluid intake?

A
  • Reduced appetite due to illness
  • Vomiting
  • Sore throat
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14
Q

What might cause additional fluid losses?

A
  • Fever

- Diarrhoea

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15
Q

What might cause increased insensible losses?

A
  • Increased sweating

- Tachypnoea

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16
Q

What might cause a loss of the normal fluid-retaining mechanisms?

A
  • Capillary leak
  • Burns
  • Permeable skin of premature infants
  • Increased urinary losses secondary to renal disease
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17
Q

Why are infants and young children more prone to dehydration than older children and adults?

A
  • Body made up of more water
  • High surface area in relation to their height or weight
  • Relatively high evaporative water losses
  • Higher metabolic rate, so higher turnover of water and electrolytes
  • Rely on others to give them fluids
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18
Q

Does dehydration itself cause death?

A

No

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19
Q

How can dehydration lead to death?

A

It can cause shock, which can lead to death

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20
Q

When does shock occur in dehydration?

A

When there is rapid loss of at least 25% of intravascular volume that is not replaced at a similar rate from the interstitial space

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21
Q

Can shock occur without dehydration?

A

Yes

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22
Q

What does the treatment of shock require?

A

Rapid administration of intravascular volume of fluid

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23
Q

What should be true of fluid administered to treat shock?

A

It should approximate in electrolyte content to plasma

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24
Q

How should dehydration without shock be treated?

A

Gradual replacement of fluids

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25
Q

What should the electrolyte content of the fluid used to treat dehydration resemble?

A

The electrolyte content of the fluid that is lost, or to the total body electrolyte content

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26
Q

What can be used to objectively measure the total body fluid changes?

A

Weight

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27
Q

How can percentage dehydration be calculated?

A

(weight before - weight after ) / weight before = % dehydration

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28
Q

What is the limitation of calculating percentage dehydration?

A

Pre-illness weight is rarely available in emergency situations

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29
Q

What can be used to assess dehydration when pre-illness weight is not available?

A

Clinical symptoms and signs

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30
Q

Why are ‘red flag’ symptoms of dehydration important?

A

They help identify children with severe dehydration at increased risk of shock

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31
Q

At what level of fluid losses does clinical dehydration become apparent?

A

> 25-50ml/kg (2.5-5%)

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32
Q

At what level of fluid losses is shock seen in dehydration?

A

Over 10%

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33
Q

What are the types of dehydration?

A
  • Isotonic/isonatraemic
  • Hypotonic/hyponatraemic
  • Hypertonic/hypernatraemic
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34
Q

What is hypotonic dehydration defined as?

A

Dehydration in association with plasma sodium concentration <135mmol/L

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35
Q

What is considered to be extreme hyponatraemia?

A

<125mmol/L

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36
Q

What is extreme hyponatraemia, or a rapid fall in serum sodium, associated with?

A
  • Cognitive impairment
  • Seizures
  • Brainstem herniation
  • Death due to cerebral oedema
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37
Q

What fluids are no longer used in paediatrics due to the risk of hyponatraemia?

A

Hypotonic crystalloid fluids, e.g. NaCl 0.18% with glucose 4%

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38
Q

What is hypertonic dehydration?

A

Dehydration with sodium >145mmol/L

39
Q

What causes hypertonic dehydration?

A

Excessive free water loss, or rarely, the administration of excess sodium

40
Q

What protects against hypernatraemia in healthy individuals?

A

Thirst and the stimulation of ADH

41
Q

When does sustained hypernatraemia predominantly occur?

A

When thirst or access to water is impaired

42
Q

Who is at the highest risk of hypernatraemic dehydration?

A

Infants, especially breastfed infants establishing lactation and infants with gastroenteritis

43
Q

What fluid shifts occur in hypernatraemia?

A

From intracellular compartment to extracellular spaces

44
Q

What does the shift of fluid from intracellular compartments to extracellular spaces in hypernatraemia lead to?

A

Cellular dehydration

45
Q

What cells are particularly vulnerable to complications arising from cellular dehydration?

A

Brain cells

46
Q

What is severe hypernatraemic dehydration associated with?

A
  • Cerebral haemorrhage
  • Seizures
  • Paralysis
  • Encephalopathy
47
Q

What can rapid rehydration with hypertonic fluids cause?

A
  • Cerebral oedema

- Central pontine myelinolysis

48
Q

What can central pontine myelinolysis lead to?

A
  • Coma
  • Convulsions
  • Death
49
Q

What is done as a result of the potential for rapid rehydration with hypertonic fluids to cause serious complications?

A

If IV therapy is required to treat dehydration, first check plasma electrolytes so rehydration fluid choice and replacement rate is appropriate

50
Q

What is meant by maintenance fluid therapy?

A

The provision of fluid and electrolytes to replace anticipated losses from breathing, sweating, and urine output

51
Q

What assumptions is maintenance fluid calculations based on?

A
  • 100kcal/kg/day of caloric requirement
  • 3ml/kg/day of urine output
  • Normal stool output
52
Q

What is the name of the formula used to calculate maintenance fluid requirements?re ma

A

Holliday-Segar formula

53
Q

How is maintenance fluid requirement calculated using the Holliday-Segar formula?

A
  • 100ml/kg/day for the first 10kg
  • 50ml/kg/day for the second 10kg
  • 20ml/kg/day for subsequent kilograms
54
Q

What is the limitation of using the Holliday-Segar formula to calculate maintenance fluid requirements in critical illness or injury?

A

Losses may be profoundly disturbed

54
Q

What is the limitation of using the Holliday-Segar formula to calculate maintenance fluid requirements in critical illness or injiry?

A
55
Q

Give an example of when maintenance fluid requirements might decrease in critical illness or injury?

A

In SIADH, secondary to acute respiratory or neurological pathology

56
Q

Why might maintenance fluid requirements be reduced in SIADH secondary to critical illness?

A

Due to reduced renal fluid loss

57
Q

How low might maintenance fluid requirements be in the context of SIADH in critical illness/injury?

A

30ml/kg/day

58
Q

Give an example of when maintenance fluid requirements might increase in critical illness or injury?

A

Acute diarrhoeal illness

59
Q

By how much might maintenance fluid requirements increase in acute diarrhoeal illness?

A

4x

60
Q

What is the first choice route for providing maintenance fluids?

A

Enteral feeds (mouth or NG tube)

61
Q

What fluid is the first choice if IV maintenance fluid is required?

A

Isotonic crystalloid fluids, e.g. NaCl 0.9% with dextrose 5%

62
Q

What is the first choice IV maintenance fluid in neonates?

A

Glucose 10% with added NaCl

63
Q

Why is glucose 10% with added NaCl the first choice IV maintenance fluid in neonates?

A

Because they have a higher glucose requirement

64
Q

What is the aim of rehydration fluid therapy?

A

To replace fluid losses and correct any electrolyte deficits

65
Q

How can the deficit volume to be replaced in rehydration fluid therapy be calculated?

A

% dehydration x weight (kg) x 10

66
Q

What is the limitation of the formula to calculate the deficit volume to be replaced in rehydration fluid therapy?

A

It requires you to know the percentage dehydration accurately, which is often not the case in clinical practice

67
Q

How is dehydration graded clinically?

A
  • No clinically detectable dehydration
  • Clinical dehydration
  • Clinical shock
68
Q

How should children with no clinically detectable dehydration be managed?

A

Regular oral intake, including breastfeeding and other milk feeds, should be encouraged

69
Q

What can be used if a child is at risk of developing dehydration?

A

Oral rehydration solution as a supplemental fluid

70
Q

How is clinical dehydration with no red flag symptoms or shock managed?

A

Rehydration via the oral route using a low osmolarity ORS

71
Q

What osmolarity of ORS is used to manage clinical dehydration?

A

240-250mOsm/L

72
Q

What volume of ORS is recommended for fluid deficit replacement in clinical dehydration?

A

50ml/kg over 4 hours

73
Q

What does fluid deficit replacement with ORS need to be given in addition to in clinical dehydration?

A

A child’s maintenance fluid

74
Q

How can ORS be given?

A

Orally or via NG tube

75
Q

When is rehydration with IV fluids indicated?

A
  • When there are red flag symptoms
  • Persistent vomiting despite NG tube administration of ORS
  • Suspected/confirmed shock
76
Q

How should cases of shock caused by dehydration be managed?

A

Rapid IV fluid bolus

77
Q

What volume of IV fluid bolus is given to treat shock caused by dehydration?

A

20ml/kg

78
Q

What IV fluid is given to treat shock caused by dehydration?

A

0.9% NaCl

79
Q

What should be done if repeated rapid fluid boluses are needed to treat shock caused by dehydration?

A

Other causes of shock need to be considered

80
Q

What should be done once the shock caused by dehydration has been resolved?

A

Rehydration can start with IV fluids

81
Q

What does the choice of fluid and rate of deficit correct depend on once resolved shock caused by dehydration depend on?

A

The serum electrolyte levels, in particular serum sodium levels

82
Q

What is used for fluid deficit replacement and maintenance in isonatraemic or hyponatraemic dehydration?

A

An isotonic solution such as 0.9% sodium chloride +/- 5% glucose

83
Q

How much fluid should be given for fluid deficit replacement in dehydrated children who initially require rapid intravenous fluid boluses for suspected or confirmed shock?

A

100mg/kg/day (added to maintenance fluid requirements)

84
Q

How much fluid should be given for fluid deficit replacement in dehydrated children who are not shocked at presentation?

A

50mg/kg/day (in addition to maintenance fluids)

85
Q

Over what time period should rehydration with IV fluid therapy be undertaken in isonatraemic or hyponatraemic dehydration?

A

3-6 hours

86
Q

Why is slow rehydration (i.e. over 24 hours) no longer recommended in isonatraemic and hyponatraemic dehydration?

A
  • Results in children remaining dehydrated for longer
  • Delays restarting oral fluids
  • Associated with longer hospital stays
87
Q

What fluid is used for fluid deficit replacement and maintenance in hypernatraemic dehydration?

A

Isotonic solutions such as 0.9% sodium chloride +/- 5% glucose

88
Q

What is the difference between fluid replacement in hypernatraemic dehydration compared to iso/hyponatraemic?

A

Fluid deficit must be replaced slowly, and typically over 48 hours

89
Q

Why should the fluid deficit be replaced more slowly in hypernatraemic dehydration?

A

It is important the serum sodium levels are reduced slowly, as rapid correction is associated with cerebral oedema

90
Q

What is the maximum rate of reduction of serum sodium levels?

A

0.5mmol/L per hour

91
Q

Why is it important to consider electrolyte disturbances when managing DKA?

A

Children presenting with DKA are often severely dehydrated, with abnormalities in glucose and sodium levels

92
Q

What is the risk of over hydration and/or rapid correction of blood sodium and glucose levels in DKA?

A

Risk of cerebral oedema

93
Q

How is shock in DKA managed?

A

10ml/kg aliquots of 0.9% sodium chloride, limiting the total fluid deficit replacement to 8% dehydration or 30ml/kg and rehydrating over 48 hours

TAS Emergencies and Critical Care ✅ (8 decks)

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