The problem
 Worldwide, dehydration is probably the most common
cause of death in childhood. In the UK, dehydration and
iatrogenic overhydration are key issues in clinical practice.
 A child suffering 10-15% dehydration will die or suffer
permanent brain damage unless managed urgently and
capably.
Why nurses?
 Nurses administer the fluids
 Nurses are responsible for ensuring that the fluids given
are safe in type and amount
 Nurses must recognise an unsafe prescription
 Under and over treatment with fluids (water and or
electrolytes) may cause severe morbidity or mortality
Fluid content as % of body weight
Water contributes to a higher percentage of body weight in child.
Fluid balance is relatively more important and fluid imbalance
causes more morbidity and mortality
Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
Body compartments
Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
Fluid distribution according to age
Younger children have a higher proportion of extra-cellular fluid.
In some forms of fluid loss, an important volume of fluid can be
lost from the extra-cellular (mostly interstitial) compartment.
Isotonic fluid is given IV to reach this compartment.
Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
Fluid distribution
Young children have a
greater proportion of water
in their interstitial
compartment
Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
Osmotic pressure
What we put into the vascular
compartment affects what is in the
other compartments
 Normally the osmotic pressure in the different body
compartments is equal.
 Differentials in osmotic pressure between two body
compartments will cause fluid to move between
compartments.
 This can be a serious problem during the acute phase of
treatment.
 Therefore – electrolytes MUST be monitored during and
(especially) after treatment.
Blood Volume
Neonate
90 ml / kg
Infants and children
80 ml / kg
Adults
65 ml / kg
Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
Electrolytes
Learn the plasma values for
these electrolytes
Water
 What is acquired from:
 Drinking
 IV fluids etc.
 Oxidation of nutrients
(carbohydrate)
Note that we make
our own water
 Water is lost through
 Renals
 Lungs
 Skin
 GI Tract
Note the avenues of
insensible loss
Insensible loss
 Water is normally lost via:
 Renals (not insensible)
 Lungs
 Skin
 GI Tract
 Obligatory loss of fluid from the
skin etc. Is influenced by:




Surface area
Environmental temperature
Humidity
Respiratory rate (lungs)
Non obligatory loss
controlled by ADH (posterior
pituitary).
ADH causes the reabsorption
of water from the renal
collecting ducts.
Insensible loss
To calculate Body Surface
Area
Insensible loss is 300ml /
M2 / day so use this
formula (left)
Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
Homeostasis
Osmo-receptors in
the hypothalamus
and elsewhere
Hypothalamus and
posterior pituitary
responsible for
sensation of thirst
(mid hypothalamus)
and releases of
antidiuretic hormone
Volume receptors
(baroreceptors) in
the atria and
elswhere
Homeostasis
The renal collective
ducts re-absorb
water
The absorption of
fluid from the gut is a
passive response to
the active transport
of sodium (failure
results in diarrhoea)
Normal Oral Fluid (Feed)
Requirements
Pre-Term
Term
Adult
• Pre-term baby needs
approximately 200ml / kg / day
• Term babies need
approximately 150ml / kg / day
• Adults need approximately
70ml / kg / day
Normal oral fluid requirements
(adapted from Behrman RE (1992)).
Age
Av. Weight (kg)
mL per kg per day
3/7
10/7
3/12
6/12
9/12
1 yr
2 yr
4 yr
6 yr
10 yr
14 yr
18 yr
3.0
3.2
5.4
7.3
8.6
9.5
11.8
16.2
20.0
28.7
45.0
54.0
80-100
125-150
140-160
130-155
125-145
120-135
115-125
100-110
90-100
70-85
50-60
40-50
Subdivision of total fluids
Fraction of Total
Function
Amount
Type
1st fifth
Insensible loss
One fifth
Insensible losses
only
2nd fifth
Essential urine
output
Two fifths
Severe fluid
restriction
3rd to 5th fifths
Maintenance of
urine output
Three fifths
Moderate fluid
restriction
Four to five fifths
Adequate fluids
Six to ten fifths
Induced diuresis
Maintenance IV requirements
First 10kg
Second 10kg
Each
additional kg
• 100 ml / kg / day for the first 10kg
body weight (4ml / kg / hour)
• 50ml / kg / day for the second 10kg
body weight (2ml / kg / hour)
• 20ml / kg / day for each additional
kg body weight (1ml / kg / hour)
 A 15kg child requires 1000ml plus 250ml =1250ml daily
Note that oral fluid requirements are higher than IV requirements.
Glasper , McEwing and Richardson (2007). Oxford handbook of children’s and young people’s nursing. Oxford University Press.
Types of IV Fluid
Fluid losses
(children)
Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
Dehydration a problem because
children have:







Higher proportion of water
Higher metabolic rate (children exchange up to 50% of the body fluid daily (adult 17%)
Higher metabolic rate (more water produced and excreted)
Higher metabolic rate = greater propensity to dehydration
Greater surface area in proportion to weight
Greater proportion of extracellular fluid
Neonates relative inability to concentrate urine on dehydration:
 Neonatal Glomerular filtration Rate is 30ml/min/1.73 m2
 At 9/12 GFR is 100ml / min / 1.73 m2
Note that circulatory failure (shock) can be highly compensated and so vital signs may mask
underlying pathology. Consequently hypotension may be a late sign of hypovolaemia.
A child is a small vessel with a large spout
An adult is a large vessel with a small spout
Therefore – children lose fluid FASTER
Dehydration
Clinical signs of dehydration
Clinical signs
Mild (<5%)
Severe (>10%)
Comments


Loss of fluid = loss of weight


? the most important sign of
severity


Measure it from the beginning
Dry mouth


Not as obvious in babies, feel
inside their cheek
Decreased skin turgor


Most obvious on abdomen
Sunken eyes


Ask parents
Tachypnoea

Late sign
Tachycardia

Late sign
Hypotension

Pre terminal sign

Only for the experienced
Decreased weight

Moderate (510%)
Drowsiness
Decreased urine output
Sunken fontanelle


Means of estimating clinical
dehydration
 Capillary refill time (should be < 2 seconds)
 Central – peripheral temperature gap (should be
< 2 degrees centigrade)
 Tissue turgur (abdomen or inside of thigh)
 3-5% weight (fluid) loss skin remains raised for
seconds



Severe malnutrition can cause reduced skin
turgur
Obesity can cause skin turgur to appear normal
Hypernatraemic dehydration associated with firm
‘thick-feeling’ skin
 Oedema
 Dry mucosa (inside cheek)
 Oligurea – Normal urine output is at least
1ml/kg/hour
 Weight change (1ml water weighs 1 gram).
Equation for dehydration
Treatment for fluid loss
(dehydration)
 Less than 5%
dehydration – treat
with Oral rehydration
solution (ORS), e.g.
dioralyte
Treatment of shock – initial Rx
 Admission to 2 hours post admission
 Weigh child
 Estimate degree of dehydration
 Measure urine output
 Give 20 ml / kg Normal saline or Colloid over 1-2 hours
 Repeat if shock not reversed
 Do electrolyte levels
 Allow IV potassium only in the presence of adequate renal
function.
Treatment of shock 2-24 hours
Give maintenance fluids plus 2/3 deficit and minus volume
already administered (20ml / kg)
Example
Weight on admission
Dehydration estimated at
 fluid deficit is
Deficit X 0.66 is
Maintenance requirement
Subtract fluid administered
Volume required over 22 hours is
9kg
10%
900ml (10% of 9kg)
594ml
900ml (100ml/kg)
180ml (20ml/kg)
1314ml
Monitor – be vigilant
Lab Serum Values
 Monitor electrolytes after infusion





and at intervals
Correct major electrolyte imbalances
SLOWLY
Monitor systemic perfusion
Monitor urine output
Monitor neurological status
Underhydration is SAFER than
overhydration
Potassium
3.5-7mmol/l
Sodium
136-146mmol/l
Types of dehydration
 Normonatraemic
 Isotonic pressure of intravascular
compartment is the same as that
in the extravascular compartment
[normal]
 Hypernatraemic
 The vascular compartment is
hypertonic
 Hyponatraemic
 The vascular compartment is
hypotonic
Na = sodium, aemia = blood, ‘Na’traemic
syn. ‘blood sodium’
Normonatraemic dehydration
 Normonatraemic
 Most common in UK
 No significant shift of fluid between intra-cellular and extracellular compartment
 Normal serum sodium is 130-150mmol/L
Hypernatraemic dehydration
 Relatively uncommon in the UK
 Serum sodium > 150mmol/L
 Can be caused by high levels of water loss with retention of sodium or
iatrogenically
 Possible causes include
 High levels of insensible fluid loss
 Diabetes incipidus
 Extra-cellular fluid is well maintained at the expense of intracellular fluid
 Clinical features underestimate the actual level of dehydration
Hyponatraemic dehydration
 Caused by the loss of fluid high in sodium
 Fluid passes into the cells
 Results in convulsions and shock which is more severe
than the level of dehydration would indicate
Shock – the three stages
 Compensated shock
 Uncompensated
 Irreversible
Compensated shock
 Normal BP
 Oligurea
 Pallor, coldness, clamminess
 Tachycardia
 Increased capillary refill time
 Anxious, agitated and confused
Uncompensated shock
 Insufficient oxygenation of tissues
 Insufficient provision of glucose to tissues
 Failure of normal metabolism
 Build up of lactic acid and carbonic acid (acidosis)
 Reduced cardiac output
 Platelet aggregation is small blood vessels (bleeding)
 Increased capillary permeability ( fluid moves from
capillaries into interstitial space)
Irreversible shock
 Damage to the renals and brain is such that even if
dehydration (hypovolaemia) is corrected and fluid
balance is restored, death will still take place
 Oxygen free radicals are released (or have been released)
and have cause irreversible major organ damage