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Fluid Balance in Children

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Presentation on theme: "Fluid Balance in Children"— Presentation transcript:

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

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