Module 1 Learning Objectives
Fluids/Electrolytes and Genetics
1. Summarize the regulation of water and electrolyte movement between
plasma and interstitial fluids and the mechanisms that result in edema
Fluid (water and small particles) move back and forth between the
vascular and interstitial areas by filtration at the capillaries. Capillary
hydrostatic pressure is the primary force promoting fluid movement
from the capillaries to the interstitial fluid. Plasma colloid osmotic
pressure is the primary force that causes interstitial fluid to move back
into the capillaries.
Water follows proteins and likes sodium. So, if sodium is present, water
will stay. If proteins move from ECF to a cell, water will follow. Vice versa.
If there is an injury, such as a burn, protein leave the cell and go into the
interstitial space, which then water follows causing edema. If sodium is
not properly excreted by the kidneys water stays which causes edema.
2. Outline the physiologic and pathophysiologic conditions leading to
electrolyte alterations and the characteristic clinical findings of plasma
excesses and deficits of potassium, calcium, magnesium, and phosphate
ions
There are 4 processes that affect the concentration of electrolytes within
the plasma:
1. Electrolyte intake: We intake electrolytes through food, drink, and
medications. Sometimes through NG or GI tubes. Even through
dialysis.
2. Electrolyte absorption: Electrolytes taken orally must be absorbed
before it is useful. Absorption of K depends on concentration
gradient, while absorption of calcium requires binding with
proteins such as Vit D. Within the GI tract many electrolytes are
bound and are prevented from being absorbed. Undigested fats
will bind to Ca and Mg and the pH of the GI tract will alter
absorption of Ca.
3. Electrolyte Distribution: the concentrations of K, Mg, and
Phosphate are higher inside the cell and lower outside the cell. Ca
is higher inside the cell; however, it is bound to other molecules.
Physiologically active ionized Ca is higher within the extracellular
fluid. Bones store Ca, Mg, and phosphate and are often referred to
electrolyte pools. The distribution of electrolytes between the
extracellular fluid and the electrolyte pool is dependent upon
hormones such as epi (K), insulin (K and phosphate), and
parathyroid hormone (Ca). Certain medications will also affect the
distribution.
4. Electrolyte Excretion: Excretion occurs through urine, feces, and
sweat. Urinary excretion is influenced by hormones. Renal tubular
flow rate also influences urinary excretion. There are also many
medications that can cause an increased excretion of urine. Fecal
excretion is influenced by the type of feces. Diarrhea increases
the excretion of K and Mg. Undigested fats binds to Ca and Mg and
