[29] Dehydration Flashcards

1
Q

What is dehydration?

A

When the body loses more fluid than it takes in

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2
Q

Is dehydration serious?

A

It can be if it is untreated

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3
Q

What % of an infants body weight is made up of water?

A

As much as 80%

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4
Q

What happens to the proportion of body water by 3 years?

A

It falls to about 65%

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5
Q

How is body water distributed?

A

Between the cells (intra-cellular) and the extracellular compartments

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6
Q

What can the extracellular compartment be further divided into?

A
  • Intravascular space

- Extravascular (interstitial) space

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7
Q

What separates the intravascular and extravascular space?

A

Capillary endothelium

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8
Q

Depletion of what compartment can lead to dehydration?

A

Any

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9
Q

What may acute loss of fluid from the intravascular compartment be associated with?

A

Shock

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10
Q

What do the clinical signs of dehydration depend on?

A

The concentration of electrolytes in the intracellular and extracellular compartments

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11
Q

What are the major ions within the extracellular compartment?

A
  • Sodium

- Bicarbonate

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12
Q

What is the major ion within the intracellular compartment?

A
  • Potassium
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13
Q

What is balanced in normal body fluids?

A

Intake and output

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14
Q

What does normal fluid balance depend on?

A
  • Fluid intake
  • Urine volume
  • Stool volume
  • Sweating
  • Insensible loss
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15
Q

When does dehydration occur, with regard to fluid balance?

A

When losses exceed input

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16
Q

Why do infants have a higher risk of dehydration?

A
  • Higher SA to weight ratio than older children, leading to greater insensible water losses
  • Higher basal fluid requirements
  • Immature renal tubular reabsorption
  • Inability to obtain fluids for themselves when thirsty
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17
Q

What are the causes of dehydration in children?

A
  • Diabetes
  • Vomiting and diarrhoea, e.g. gastroenteritis
  • Heatstroke
  • Fever
  • Conditions that make it hard to swallow fluids, e.g. sore throat
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18
Q

What are the risk factors for dehydration?

A
  • Infants
  • Children that have passed 6 or more diarrhoeal stools in the previous 24 hours
  • Children that have had vomiting 3 or more times in the previous 24 hours
  • Children that have been unable to tolerate, or not offered, oral fluids
  • Children with malnutrition
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19
Q

What infants in particular are at risk of dehydration?

A
  • Under 6 months of age

- Low birthweight

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20
Q

What are the symptoms of dehydration?

A
  • Feeling thirsty
  • Dark yellow and strong-smelling urine
  • Feeling dizzy or lightheaded
  • Feeling tired
  • Reduced urine output
  • Few or no tears when crying
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21
Q

What needs to be determined in the history in dehydration?

A
  • Cause of dehydration

- Severity of dehydration

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22
Q

What are the signs of dehydration?

A
  • Sunken eyes
  • Soft spot on head sinks inwards
  • Cold and blotchy-looking hands and feet
  • Dry mouth, lips, and eyes
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23
Q

What do you need to assess/obtain on physical examination in dehydration?

A
  • Weight
  • Severity of dehydration
  • Signs of cause of dehydration
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24
Q

What is the importance of measuring the weight in dehydration?

A

Acute water loss can be estimated from the difference between actual weight and a recent weight made before dehydration occurred, and so regular weighing will allow accurate measurement of fluid replacement

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25
Q

How can the cause of dehydration be assessed on examination?

A

Should perform a thorough examination to identify the foci of infection

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26
Q

What should be included on thorough examination to identify the cause of dehydration?

A
  • Ears
  • Throat
  • Chest
  • Abdomen
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27
Q

What physical things etc signs should be assessed when determining the severity of dehydration?

A
  • Mental state
  • Skin turgor
  • Dryness of mucous membranes
  • Fontanelle
  • Eye turgor
  • Skin perfusion
  • Pulse rate and character
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28
Q

What are the signs of mild dehydration?

A

Only physical sign may be dry mouth

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29
Q

What are the physical signs of moderate dehydration?

A
  • Lethargy
  • Inelastic skin
  • Sunken fontanelle
  • Sunken eyes
  • Pulse may be fast, but of normal volume
  • Slow refilling of skin when blanched
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30
Q

What are the signs of severe dehydration?

A
  • Very confused, only semi-conscious
  • Mottled skin
  • No refilling of skin when blanched
  • Fontanelle and eyes deeply sunken
  • Poor eye turgor
  • Thready and fast pulse
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31
Q

Why is it important to assess how severe dehydration is?

A

So you can calculate how much fluid replacement is required

32
Q

What investigations should be done in dehydration?

A
  • U&s

- Urine assessment

33
Q

What findings may be present on U&Es in dehydration?

A
  • Hyper or hyponatraemia

- Low bicarbonate

34
Q

Why can hyper or hyponatraemia occur in dehydration?

A

Due to differential loss of sodium

35
Q

What is the importance of identifying hyper or hyponatraemia in dehydration?

A

It will change your management

36
Q

When might you get low bicarbonate in dehydration?

A

As a result of diarrhoea

37
Q

What does low bicarbonate due to diarrhoea cause?

A

Metabolic acidosis

38
Q

What metabolic abnormality may occur if there has been excessive vomiting?

A

Excessive loss of hydrogen ions, which may cause an initial metabolic alkalosis

39
Q

What urine assessments should be done in dehydration?

A

Assess urine for specific gravity or osmolality, and consider measuring urine electrolytes

40
Q

Should an assessment of urinary volume over a known period be done in dehydration?

A

It is helpful, but difficult to collect, and treatment should not be delayed to measure urine output

41
Q

What are the different types of dehydration?

A
  • Isotonic
  • Hyponatraemic
  • Hypernatraemia
42
Q

What is the most common type of dehydration?

A

Isotonic

43
Q

What is isotonic dehydration?

A

When there are equal losses of sodium and water

44
Q

Will the seurm sodium be high, normal, or low in isotonic dehydration?

A

Normal

45
Q

How do the physical signs of dehydration correlate to the fluid loss in isotonic dehydration?

A

The physical signs will be proportional to the degree of fluid loss

46
Q

Define clinically hyponatraemic dehydration?

A

Dehydration with serum sodium <130mmol/L

47
Q

Physiologically, when does hyponatraemic dehydration occur?

A

Generally, when fluid losses have been replaced with hypotonic solutions such as water

48
Q

How does hyponatraemic dehydration present?

A

The child will be lethargic, and skin dry and inelastic

49
Q

What is hypernatraemic dehydration clinically defined as?

A

Dehydration when serum sodium is >150mmol/L

50
Q

When is hyponatraemic dehydration more likely?

A
  • Acute and severe water loss
  • Common in breast-fed baby in first 2 weeks of life
  • Concentrated formula feeds
51
Q

Why might hyponatraemic dehydration occur in a breastfed baby in the first two weeks of life?

A

If there is difficulty establishing feeds

52
Q

What might lead to a parent giving a baby concentrated formula feeds?

A

The parent incorrectly measuring scoops of powdered milk

53
Q

How does hypernatraemic dehydration present?

A

Infant appears very hungry, but has fewer clinical signs of dehydration. The skin feels doughy.
Metabolic acidosis is a common feature

54
Q

What % dehydration is considered to be mild?

A

5%

55
Q

How can a child with mild dehydration be treated?

A

May be treated at home using oral hydration therapy

56
Q

When is oral rehydration likely to be successful in dehydration?

A

When vomiting is not a major feature

57
Q

What should be used in oral rehydration therapy?

A

Oral rehydration solutions such as Dioralyte

58
Q

In what forms can oral rehydration solutions such as Dioralyte be dispensed?

A
  • Oral solution

- Effervescent tablets or powders

59
Q

Should breast feeding be maintained when using oral rehydration solutions?

A

Yes

60
Q

When can normal milk feed be resumed in dehydration if the baby is bottle fed?

A

Once diarrhoea has settled

61
Q

When do you need to pay closer attention to the fluid balance in dehydration?

A

In a child with more significant dehydration, particularly if there is vomiting

62
Q

What do you do in assessment of the fluid balance in a significantly dehydrated child involve?

A
  • Maintaining an accurate input-output chart
  • Weighing the child twice daily
  • Frequent measurement of serum electrolytes
63
Q

What principles do the calculations of rehydration require?

A
  • Estimate or acute fluid loss
  • Estimate of maintenance fluid requirements
  • Estimate of on-going losses
64
Q

How is an estimate of acute fluid loss made?

A

Difference between actual weight and recent normal weight

65
Q

What should be done if recent normal weight is unknown when estimating acute fluid loss?

A

Rely on clinical assessment of dehydration

66
Q

What is the estimated maintenance fluid requirement for a 0-6 month old?

A

150mL/kg/24 hours

67
Q

What is the estimated maintenance fluid requirement for a 6-12 month old?

A

120mL/kg/24 hours

68
Q

What is the estimated maintenance fluid requirement for a 12-24 month old?

A

100mL/kg/24 hours

69
Q

What is the estimated maintenance fluid requirement for a >24 month old?

A

80mL/kg/24 hours

70
Q

How are on-going losses estimated in dehydration?

A

If possible, they should be measured carefully on an hourly basis, and added to the fluid regimen every 4 hours

71
Q

What does the rate of rehydration depend on?

A

The type of dehydration

72
Q

How should rehydration be given if the patient is shocked?

A

Circulation must be restored by boluses of colloid

73
Q

How should rehydration be given if hypernatraemia dehydration?

A

Must correct more slowly over 48 hours

74
Q

Why is it important to correct hypernatraemic dehydration slowly?

A

To avoid rapid shifts of water within the brain resulting in cerebral oedema

75
Q

What are the complications of dehydration?

A
  • Shock
  • Severe metabolic acidosis
  • Death