Fluid Balance

1. Fluid Balance

2. Learning Outcomes Understand the principals of fluid balance To appreciate the difference of water and fluid distribution in the newborn, children and adults. Understand, and define key terminology Explain the fate of a red blood cell in a hypotonic, isotonic and hypertonic solution. How electrolytes and proteins effect fluid distribution Homeostatic mechanisms of ADH and RAA pathway that attempt to maintain fluid balance The action of diuretic Basic conditions effect on fluid balance

3. Water Balance Water Intake = Drink (neonate milk) Food (neonate milk) Metabolism Impaired renal function (risk fluid overload = hypervolemia causing pulmonary oedema, hypertension, breathlessness, hypoxia) Water losses Urine Faeces Insensible losses (expired air + adults sweat) Diarrhoea Vomiting (risk dehydration = hypovolemia leading to shock)

4. Terminology Osmolarity: - Is the measure of solute particles per litre of solution (High solute conc. = high attraction of water) Oncotic Pressure: - The effect of plasma proteins also called colloid pressure (High oncotic conc. = high attraction of water) Hydrostatic Pressure: - Is the mechanical force of water pushing against a cellular membrane

5. Osmosis Definition: - Water moves down a concentration gradient across a semi-permeable membrane. From an area of high water concentration to an area of low water concentration.

6. Red blood cells Isotonic beaker Hypotonic beaker Hypertonic beaker

7. Body water content Age Water Content of body Premature Infant 90% Newborn Infant 70-80% 12-24 months 64% Adult 60% Willock & Jewkes (2000). Making Sense of fluid balance in children. Paediatric Nursing. 12. 7, 37-42.

8. Fluid distribution Intracellular fluid Extracellular fluid Newborn Infant 47% 53% 12 months 53% 47% 24 months 60% 40% Adult male 67% 33% Intracellular = fluid inside cells Extracellular = fluid outside cells Willock & Jewkes (2000). Making Sense of fluid balance in children. Paediatric Nursing. 12. 7, 37-42.

9. Composition of body fluids Electrolyte Plasma conc. Intracellular conc. (mmol/l) (mmol/l) Na+ 133-147 10 K+ 3.4-5.2 150 High sodium = Hypernatraemia High potassium= Hyperkalaemia Willock & Jewkes (2000). Making Sense of fluid balance in children. Paediatric Nursing. 12. 7, 37-42.

10. Questions Sodium is osmotically active, where is most sodium found? What would happen if sodium increased in this compartment? What would happen if sodium decreased in this compartment? Where is potassium mostly found? If the albumin conc. of the blood fell, what would happen to the water in the blood?

12. Role of ADH in dehydration

13. Role of ADH in dehydration continued...

14. Renin, Angiotensin, Aldosterone (RAA) Pathway

15. Action of Diuretics

16. Action of Diuretics continued...

17. Questions What are diuretics general mechanism of action? Why might diuretics be given to hypertensive patients? Why are diabetic patients thirsty and produce high volumes of urine? What is Diabetes insipidus? Which hormone affects water balance short term and how does it work? Long term a fall in BP and fluid volume is regulated by which system and how does it work?