1. Fluid Balance in Children

2. 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.

3. 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

4. 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

5. Body compartments
Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42

6. 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

7. 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

8. What we put into the vascular compartment affects what is in the other compartments
Osmotic pressure
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.

9. Blood Volume Neonate 90 ml / kg Infants and children 80 ml / kg Adults
Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42

10. Learn the plasma values for these electrolytes

11. Water Water is lost through What is acquired from: Renals Drinking
Lungs
Skin
GI Tract
What is acquired from:
Drinking
IV fluids etc.
Oxidation of nutrients (carbohydrate)
Note that we make our own water
Note the avenues of insensible loss

12. Insensible loss Water is normally lost via: Renals (not insensible)
Non obligatory loss controlled by ADH (posterior pituitary).
ADH causes the reabsorption of water from the renal collecting ducts.
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)

13. 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

14. Homeostasis Homeostasis
Osmo-receptors in the hypothalamus and elsewhere
Hypothalamus and posterior pituitary responsible for sensation of thirst (mid hypothalamus) and releases of antidiuretic hormone
The absorption of fluid from the gut is a passive response to the active transport of sodium (failure results in diarrhoea)
The renal collective ducts re-absorb water
Volume receptors (baroreceptors) in the atria and elswhere

15. Normal Oral Fluid (Feed) Requirements
Pre-Term
Pre-term baby needs approximately 200ml / kg / day
Term
Term babies need approximately 150ml / kg / day
Adult
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
3.0
80-100
10/7
3.2
3/12
5.4
6/12
7.3
9/12
8.6
1 yr
9.5
2 yr
11.8
4 yr
16.2
6 yr
20.0
90-100
10 yr
28.7
70-85
14 yr
45.0
50-60
18 yr
54.0
40-50

16. 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

17. Maintenance IV requirements
First 10kg
100 ml / kg / day for the first 10kg body weight (4ml / kg / hour)
Second 10kg
50ml / kg / day for the second 10kg body weight (2ml / kg / hour)
Each additional kg
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.

18. Types of IV Fluid

19. Fluid losses (children)
Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42

20. 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

21. Clinical signs of dehydration
Clinical signs
Mild (<5%)
Moderate (5-10%)
Severe (>10%)
Comments
Decreased weight 
Loss of fluid = loss of weight
Drowsiness
? the most important sign of severity
Decreased urine output
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
Hypotension
Pre terminal sign
Sunken fontanelle
Only for the experienced

22. 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).

23. Equation for dehydration

24. Treatment for fluid loss (dehydration)
Less than 5% dehydration – treat with Oral rehydration solution (ORS), e.g. dioralyte

25. 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.

26. Treatment of shock 2-24 hours
Give maintenance fluids plus 2/3 deficit and minus volume already administered (20ml / kg)
Example
Weight on admission 9kg
Dehydration estimated at 10%
 fluid deficit is ml (10% of 9kg)
Deficit X 0.66 is ml
Maintenance requirement 900ml (100ml/kg)
Subtract fluid administered 180ml (20ml/kg)
Volume required over 22 hours is 1314ml

27. Monitor – be vigilant
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
Lab Serum Values
Potassium
3.5-7mmol/l
Sodium
mmol/l

28. Na = sodium, aemia = blood, ‘Na’traemic syn. ‘blood sodium’
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’

29. Normonatraemic dehydration
Most common in UK
No significant shift of fluid between intra-cellular and extra-cellular compartment
Normal serum sodium is mmol/L

30. 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

31. 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

32. Shock – the three stages
Compensated shock
Uncompensated
Irreversible

33. Compensated shock Normal BP Oligurea Pallor, coldness, clamminess
Tachycardia
Increased capillary refill time
Anxious, agitated and confused

34. 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)

35. 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

36. Fluid Balance in Children