Fluid and Electrolytes

• -Normal ECF has a ratio of 20 parts bicarbonate (HCO3-) to 1 part carbonic acid (H2CO3)
• -Carbonic acid and bicarbonate must be controlled to maintain the ratio
• -If the ratio changes, so will the pH
• -Lungs assist in regulating the production of carbonic acid
• -Kidneys assist by regulating the production of bicarbonate

-Active in the intracellular fluids, particularly the renal tubules

-Converts alkaline sodium phosphate (Na2HPO4), a weak base, to an acid–sodium phosphate (NaJ2PO4) in the kidneys

-Plasma proteins and hemoglobin possess chemical groups that combine or liberate hydrogen ions

-Excess hydrogen ions in the blood cross the plasma membrane and bind to hemoglobin molecules

• -A buffer is a substance that prevents body fluids from becoming overly acidic or alkaline.
• -Buffers can:Combine with excess acids or bases to prevent major changes in pH
• -Work like a base and bind with a free hydrogen ion
• -Work like an acid and release hydrogen ions

-lungs regulate acid–base balance by eliminating or retaining carbon dioxide

-can change pH rapidly: within minutes

-Blood levels of carbonic acid and carbon dioxide rise as RR increase (to blow off carbon dioxide).

-Blood levels of carbonic acid and carbon dioxide fall as RR decrease (carbon dioxide is retained).

-Acidosis: kidneys excrete hydrogen ions => conserve bicarbonate ions => raises pH to the normal range (7.35–7.45).

-Alkalosis:  kidneys retain hydrogen ions => excrete bicarbonate ions => lowers pH to the normal range.

-Acid–base balance by the kidneys occurs slowly. Approx. 3 days to return pH to normal.

-a substance that releases hydrogen ions in a solution and has a pH value less than 7.

-a substance that retains hydrogen ions in a solution and has a pH value greater than 7.

-a condition characterized by an excess of hydrogen ions or loss of base ions (bicarbonate) in the ECF.

-The pH falls below 7.35. Death will occur if the pH falls below 6.80.

-a condition characterized by a lack of hydrogen ions or a gain of base ions (bicarbonate).

-The pH rises above 7.45. Death will occur if the pH rises above 7.80.

-fluid found within the cells

-comprises two thirds of the total body fluid.

-ICF contains oxygen, electrolytes, and glucose along with water.

• -found outside the cells
• -carries oxygen and nutrients to body cells, and carries waste products away from body cells. 
• -comprises one third of the total body fluid.
• -two compartments: intravascular and interstitial.

• -aka plasma
• -accounts for 20% of the ECF.

• -accounts for 75% of the ECF
• -fluid that surrounds the cells.

• -5% of the ECF
• -Ex:Cerebrospinal, pericardial, pancreatic, pleural, intraocular, biliary, peritoneal, and synovial fluids

• -Sodium (Na+)
• -Potassium (K+)
• -Calcium (Ca2+)
• -Magnesium (Mg2+)

• -Chloride (Cl-)
• -Bicarbonate (HCO3-)
• -Phosphate (HPO42-)
• -Sulfate (SO42-)

• -Substances that dissolve in a liquid
• -Oxygen,
• -carbon dioxide,
• -glucose,
• -urea,
• -amino acids,
• -protein

• -a solution that can dissolve a solute.
• -Water is a solvent.

-The concentration of solutes in body fluids is expressed as osmolality.

- total solute concentration within a fluid compartment 

-Sodium is the greatest determinant of osmolality of plasma

-Potassium, glucose, and urea are determinants of osmolality of ICF

• -0.9% NaCl (normal saline)
• -Normal saline is administered with blood products
• -Ringer lactate (balanced electrolyte solution)
• -5% dextrose in water (D5W)
• -Have the same concentration of solutes as blood plasma
• -Used to restore vascular volume
• -Assess clients for signs of hypervolemia (i.e., bounding pulse and dyspnea)

• -5% dextrose in normal saline (D5NS)
• -5% dextrose in 0.45% NaCl (D51/2NS)
• -5% dextrose in Ringer lactate (D5LR)
• -Greater concentration of solutes than plasma
• -Draw fluid out of ICF and interstitial compartments into the vascular compartment
• -Expand vascular volume
• -Do not administer to clients with kidney or heart disease, or if dehydrated
• -Assess for hypervolemia

• -0.45% NaCl (half normal saline)
• -0.33% NaCl (one-third normal saline)
• -Provides free water and treats cellular dehydration
• -Promotes waste elimination by the kidneys
• -Do not administer if client is at risk for increased intracranial pressure or fluid shift

-Osmotic pressure allows the solution to pull water across the semipermeable membrane.

-the solution with the higher solute concentration exerts a higher osmotic pressure.

-water is pulled across the membrane to equalize the concentrations of the solutions.

-Opposes Hydrostatic pressure

-the movement of solutes across a semipermeable membrane from higher to lower concentration.

-the diffusion of water across the cell membrane from lower to higher concentration.

-equalizes water and solute.

-maintains homeostasis and fluid balance

-the movement of fluid and solutes together across a semipermeable membrane from an area of higher pressure to one of lower pressure.

-occurs when fluids and nutrients in the body move from the capillaries to the interstitial fluid around the cells.

-force exerted by the blood against the blood vessel walls is hydrostatic pressure.

-Osmotic pressure opposes hydrostatic pressure, holding fluid in the vascular compartment to maintain vascular volume.

-If the hydrostatic pressure is greater than the osmotic pressure, fluid filters out of the blood vessels.

-The movement of solutes across the cell membrane from a less concentrated solution to a more concentrated one.

-requires metabolic energy.

-A substance combines with a carrier and moves it inside the cell membrane.

-maintains the differences between sodium and potassium concentrations in ECF and ICF.

1 L of fluid gained or lost

• increases with dehydration
• decreases with overhydration

• Antidiuretic hormone (ADH):
• Renin-angiotensin-aldosterone system:
• Atrial natriuretic factor (ANF):