Cations – transmit nerve impulses to muscles and contract skeletal and smooth muscles (K, Na,
Ca, Mg), positive charge (t is like the plus sign)
Anions – attached to cations (CL, HCO3, PO4, SO4), negative charge (n reminds you of
negative)
Osmolality – concentration of body fluid, normal is 275 – 295, if less is hypo-osmolar (result of
excess water intake or fluid overload caused by an inability to excrete excess water, if more is
hyperosmolar (caused by severe diarrhea, increased salt and solutes (protein) intake, inadequate
water intake, diabetes, ketoacidosis or sweating)
Sodium – main extracellular electrolyte, major fxn is to regulate body fluids
Isotonic solutions – D5W, NS, LR, Ringer’s solution, very similar to extracellular and intracellular
fluids, used with fluid volume loss; D5W when given rapidly or continuously will become hypotonic
because dextrose is rapidly metabolized into water and carbon dioxide
Crystalloids – dextrose, saline, LR, used for replacement and maintenance fluid therapy
Colloids – volume expanders, dextran solutions, amino acids, hetastarch, plasmanate, dextran is
not a substitute for whole blood because it doesn’t have any products that can carry oxygen,
hetastarch is isotonic and can decrease platelet and hematocrit counts and is contraindicated in
bleeding disorders, CHF, renal dysfunction, plasmanate can be used instead of plasma or
albumin to replace body protein
Blood and blood products – whole blood, packed RBCs, plasma, albumin
Lipids – fat emulsion solutions, indicated when IV therapy lasts longer than 5 days
Daily water need – 2000 ml/day average, 15 ml/pound, increase by 15% if pt has fever
Potassium – 20 times more prevalent in cells than in vessels, 3.5 – 5.3, narrow normal range, too
little or too much can lead to cardiac arrest, poorly stored in the body so give it daily, bananas
and dried fruits are higher than oranges and fruit juices, necessary for transmission and
conduction of nerve impulses and for contraction of skeletal, cardiac and smooth muscles; given
with an anion (ie. Chloride or bicarb), extremely irritating to the GI and intestinal tract so give with
glass of fluid, IV K must be diluted in IV fluids, cannot be given as a bolus or push, always must
be diluted
Hypokalemia – when cells are damaged from trauma, injury, surgery or shock, potassium leaks
from the cells into the intravascular fluid and is excreted by the kidneys, with cellular loss of
potassium it shifts from the blood plasma into the cell to restore the cellular potassium balance
leading to hypokalemia, vomiting and diarrhea also decreases K levels; s/s – nausea, vomiting,
dysrhythmias, abdominal distention, soft flabby muscles; for low levels encourage foods high in
potassium (ie. fruit juice, citrus fruits, dried fruits, bananas, nuts, veggies); certain drugs promote
K loss – hydrochlorothiazide, Lasix (potassium-wasting diuretics), cortisone preparations; if they
take these drugs they need to eat more foods with potassium; use potassium cautiously in pts
with renal insufficiency, be cautious is urine output is less than 600 ml/day
Drugs – there are potassium-wasting diuretics (excrete K, Na, Cl in the urine) and potassiumsparing diuretics (retain K but excrete Na, Cl in the urine); laxatives, corticosteroids, antibiotics,
potassium-wasting diuretics are the major drug groups that cause hypokalemia; oral and IV
potassium salts, CNS agents, potassium-sparing diuretics can cause hyperkalemia
Hyperkalemia – if the kidneys shut down or are diseased, K accumulates in the intravascular
fluid, caused by renal insufficiency or administration of large doses of K over time, for mild
elevation restrict foods high in K, to immediately decrease K levels use sodium bicarbonate,
calcium gluconate or insulin and glucose or Kayexalate with sorbitol (this drug therapy exchanges
a NA ion for a K ion in the body and is a more permanent means of correcting hyperkalemia), s/s
– nausea, abdominal cramps, oliguria, tachycardia or late bradycardia, weakness, numbness or
tingling in the extremities
Sodium – major cation in the ECF, normals 135-145, regulates body fluids, promotes the
transmission and conduction of nerve impulses, part of the sodium/potassium pump that causes
cellular activity; Na shifts into cells as K shifts out of cells repeatedly to maintain water balance
and neuromuscular activity, Na combines readily with Cl or HCO3 to promote acid-base balance
Hyponatremia – can result from vomiting, diarrhea, surgery, potent diuretics; s/s – muscle
weakness, headaches, abdominal cramps, nausea, vomiting; can give NS to increase sodium
content in the vascular fluid
Hypernatremia – requires sodium restriction; s/s – flushed skin, elevated body temp, elevated BP,
rough dry tongue; can result from consuming certain drugs (cortisone, cough meds, some
antibiotics)
Water – essential nutrient, more important to life than any other nutrient, body needs more water
each day than any other nutrient, can survive only a few days without water, minerals help the
body maintain an appropriate balance and distribution of water, 60% of an adult’s body weight,
more in a child
Carries nutrients and waste products
Maintains the structure of large molecules
Participates in metabolic reactions
Serves as a solvent for minerals, vitamins, amino acids, glucose
Acts as a lubricant and cushion around joints, eyes, spinal cord
Aids in regulation of normal body temp
Maintains blood volume
Water intake – when the blood becomes concentrated (having lost water but not the dissolved
substances in it) the mouth gets dry and the hypothalamus initiates drinking behavior, thirst lags
behind the body’s need, first sign of dehydration is thirst, if you can’t get fluid or don’t perceive the
thirst message you get dehydrated rapidly; water intoxication leads to hyponatremia
Water sources – water itself and other beverages, fruits and veggies have up to 90% water,
meats and cheeses contain 50%, water is also generated during metabolism, caffeine can be
counted towards total intake, alcohol acts as a diuretic and dehydrates you
Fluids maintain blood volume which, in turn, influences blood pressure, central to the regulation of
blood volume and BP are the kidneys, instructions on whether to retain or release substances or
water comes from ADH, rennin, angiotensin and aldosterone (see Figure 12-3, pg 401 Nutrition)
ADH – retains water; (also called vasopressin) whenever BP or blood volume falls too low or
extracellular fluid becomes too concentrated they hypothalamus signals the pituitary gland to
release ADH, this is a water conserving hormone that stimulates the kidneys to reabsorb water,
so the more water you need the less your kidneys excrete, this also triggers thirst
Renin – retains sodium; cells in the kidney release renin in response to low blood pressure
causing the kidneys to reabsorb sodium, sodium reabsorption is always accompanied by water
retention which restores blood volume and BP
Angiotensin – constricts blood vessels; renin also activates angiotensin which is a powerful
vasoconstrictor which raises BP
Aldosterone – retains sodium; angiotensin causes the release of aldosterone from the adrenal
glands, it signals the kidneys to retain more sodium and water, the effect is that when more water
is needed less is excreted
Cells – must maintain a balance of 2/3 body fluids inside the cells and 1/3 body fluids outside
cells, if too much water enters then the cell can rupture, if too much water leaves cells can
collapse; to control the movement of water, the cells direct the movement of the major minerals
If an anion enters the fluid, a cation must accompany it or another anion must leave so that
electrical neutrality is maintained, it’s a good bet that whenever Na and K ions are moving, they
are going in opposite directions
Electrolytes attract water, some electrolytes reside outside cells (sodium, chloride) and some
inside cells (K, Mg, PO4, SO4), cell membranes are selectively permeable (they allow passage of
some molecules but not others), whenever electrolytes move across the membrane water follows,
proteins attract water and help to regulate fluid movement, regulation occurs mainly in the GI tract
and the kidneys
Na and Cl are the most easily lost because they are the primary extracellular electrolytes,
sweating, bleeding or excretion
Start at pg 404, Acid-Base balance