Fluid Balance in Children

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

10. Electrolytes Learn the plasma values for these electrolytes

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

12. Insensible loss 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

15. Normal Oral Fluid (Feed) Requirements

16. Subdivision of total fluids

17. Maintenance IV requirements • 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. Dehydration

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 900ml (10% of 9kg) Deficit X 0.66 is 594ml 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

28. 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 • Normonatraemic • Most common in UK • No significant shift of fluid between intra-cellular and extra-cellular compartment • Normal serum sodium is 130-150mmol/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