Fluid, Electrolyte & Acid-Base Balance

Body FluidsYour body is 66% waterNot evenly distributed separated into compartmentsAble to move back and forth thru the cell membranes to maintain an equilibrium

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

EdemaCondition 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

Fluid BalanceAmount in = amount outAverage 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?

Electrolyte BalanceDef: - concentration of individual electrolytes in the body fluid compartments is normal and remains relatively constant. Electrolytes are dissolved in body fluidsSodium predominant extracellular cation, and chloride is predominant extracellular anion. Bicarbonate also in extracellular spaces

Electrolyte BalancePotassium is the predominant intracellular cation and phosphates are the predominant intracellular anionCations are actively reabsorbed, anions passively follow by electrochemical attractionAldosterone works at kidney tubules to regulate sodium & potassium levels

Electrolyte BalanceBecause of sodium and potassium influence, water will move between compartmentsExample: if high [sodium], then water will move from intracellular space to extracellular space due to osmotic pressure

Balance of other ElectrolytesCalcium hypercalcemia / hypocalcemiaMagnesium hypermagnesemia/ hypomagnesemiaPhosphate hyperphosphatemia/ hypophosphatemiaChloride hyperchloremia/ hypochloremia

Acid - Base BalanceBlood - normal pH of 7.2 7.45< 7.2 = acidosis > 7.45 = alkalosis3 buffer systems to maintain normal blood pHBuffersRemoval of CO2 by lungsRemoval of H+ ions by kidneys

BuffersProtein Buffer SystemsAmino Acid buffersHemoglobin buffersPlasma Protein buffersPhosphate Buffer SystemsCarbonic Acid Bicarbonate Buffer System

Maintenance of Acid-Base BalanceRespiratory 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

Disturbances to Acid-Base BalanceRespiratory AcidosisRespiratory AlkalosisMetabolic Acidosis [ lactic acidosis, ketoacidosis]Metabolic Alkalosis

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