Fluid, Electrolyte & Acid-Base Balance

1. Fluid, Electrolyte & Acid-Base Balance

2. Body Fluids • Your body is 66% water • Not evenly distributed – separated into compartments • Able to move back and forth thru the cell membranes to maintain an equilibrium

3. Fluid Compartments • Intracellular fluid – fluid inside cells [ICF] • Extracellular fluid – fluid outside cells and all other body fluids --- ¼ is plasma [intravascular fluid], remaining ¾ is interstitial fluid. Small amount is localized as CSF, serous fluid, synovial fluid, humors of eye & endo/perilymph of ears

5. Edema • Condition in which fluid accumulates in the interstitial compartment. Sometimes due to blockage of lymphatic vessels or by a lack of plasma proteins or sodium retention

6. Fluid Balance • Amount in = amount out • Average daily intake is 2500 ml [ fluids, food and metabolic water] • Average daily output is 2500 ml [ urine, feces, perspiration, insensible perspiration] • What can throw off these numbers?

7. Electrolyte Balance • Def: - concentration of individual electrolytes in the body fluid compartments is normal and remains relatively constant. • Electrolytes are dissolved in body fluids • Sodium predominant extracellular cation, and chloride is predominant extracellular anion. Bicarbonate also in extracellular spaces

8. Electrolyte Balance • Potassium is the predominant intracellular cation and phosphates are the predominant intracellular anion • Cations are actively reabsorbed, anions passively follow by electrochemical attraction • Aldosterone works at kidney tubules to regulate sodium & potassium levels

10. Electrolyte Balance • Because of sodium and potassium influence, water will move between compartments • Example: if high [sodium], then water will move from intracellular space to extracellular space due to osmotic pressure

11. Balance of other Electrolytes • Calcium – hypercalcemia / hypocalcemia • Magnesium – hypermagnesemia/ hypomagnesemia • Phosphate – hyperphosphatemia/ hypophosphatemia • Chloride – hyperchloremia/ hypochloremia

12. Acid - Base Balance • Blood - normal pH of 7.2 – 7.45 • < 7.2 = acidosis > 7.45 = alkalosis • 3 buffer systems to maintain normal blood pH • Buffers • Removal of CO2 by lungs • Removal of H+ ions by kidneys

13. Buffers • Protein Buffer Systems • Amino Acid buffers • Hemoglobin buffers • Plasma Protein buffers • Phosphate Buffer Systems • Carbonic Acid – Bicarbonate Buffer System

14. Maintenance of Acid-Base Balance • Respiratory System: removal of CO2 by lungs – stabilizes the ECF, has direct effect on Carbonic Acid – Bicarbonate Buffer System • Urinary System: removal of H+ ions by kidneys

15. Disturbances to Acid-Base Balance • Respiratory Acidosis • Respiratory Alkalosis • Metabolic Acidosis [ lactic acidosis, ketoacidosis] • Metabolic Alkalosis

16. www.nda.ox.ac.uk/ wfsa/html/u13/u1312_02.htm