Fluid, Electrolyte & Acid-

Base Balance

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

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

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

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?

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

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

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

Balance of other Electrolytes

Calcium – hypercalcemia / hypocalcemia

Magnesium – hypermagnesemia/

hypomagnesemia

Phosphate – hyperphosphatemia/

hypophosphatemia

Chloride – hyperchloremia/

hypochloremia

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

1. Buffers

2. Removal of CO2 by lungs

3. Removal of H+ ions by kidneys

Buffers

Protein Buffer Systems

Amino Acid buffers

Hemoglobin buffers

Plasma Protein buffers

Phosphate Buffer Systems

Carbonic Acid – Bicarbonate Buffer

System

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

Disturbances to Acid-Base

Balance

Respiratory Acidosis

Respiratory Alkalosis

Metabolic Acidosis [ lactic acidosis,

ketoacidosis]

Metabolic Alkalosis

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