ICF-intracellular fluid compartment- inside cells 2/3 of total body water
ECF-extra-cellular fluid compartment- 1/3 of body fluid that is outside the
cells.
a. plasma- plasma membranes separate the ICF from the ECF
b. interstitial spaces- between the cells, the capillary membranes
separate plasma from the interstitial fluid.
Osmolality of fluid is determined by the number of dissolved particles or
solutes in 1 kg (1 L) of water.
In most body fluids 3 solutes determine the osmolality:
Sodium- greatest factor in osmolality bc of its abundance
Glucose
Urea
Normal osmolality of body fluids: 275-295 mOsm/kg
Tonicity-ability of a solution to cause a change in water movement across a
membrane due to osmotic forces.
EX. Normal plasma is considered ISOTONIC
Isotonic- solutions with same osmolality as the blood
Hypertonic- solutions have HIGHER concentration of solutes than plasma
Hypotonic- solutions have LOWER concentration of solutes than plasma.
Osmosis- water moves from area of low concentration(low osmolality) to
area of higher concentration.(high osmolality)
If a hypertonic IV solution is administered the plasma gains more solutes
than the interstitial fluid, therefore water will move by osmosis from the
interstitial fluid to the plasma.(Expanded plasma volume)
If a hypotonic IV solution is administered water will move from the plasma
to the interstitial fluid. (smaller plasma volume)
DIAGRAMS p. 653
Avg adult water intake of 2500ml/day
Most important regulator of fluid intake is THIRST.(the hypothalamus
senses a hypertonic ECF.)
Kidney- primary regulators of fluid output. Aldosterone is secreted by the
adrenal cortex, which causes the kidney to retain sodium and water. This
increases the osmolality of the ECF. Then a 2nd hormone, ADH(anti-diuretic
hormone) is released during periods of high plasma osmolality. ( increases
water reabsorption)
2 kinds of IV replacement fluids:
Colloids- proteins or other large molecules that remain in the blood for a
long time because they are TOO LARGE to cross the capillary
membranes.(therefore, move VERY SLOWLY across membranes)
They draw water molecules FROM the cells and tissues INTO the plasma.
These are called PLASMA VOLUME EXPANDERS.
Dextran 40- given as IV increases BP, Heart rate, Cardiac output, improved
venous return. Used in pts with hypovolemic shock due to burns,
hemorrhage, surgery and shock.
Can also be used to prevent DVT and pulmonary emboli.
Colloid IV Solutions:
5% Albumin
Dextran 40 in D5W or NS
Dextran 70 in NS
Hetastarch 6% in NS
Plasma Protein Fraction:
83% albumin
17% plasma globulins
Used in treating: hypovolemic shock due to burns, hemorrhage, surgery.
Prior to giving colloid iv: CBC, Serum electrolytes, BUN, if pt is dehydrated
can cause renal failure. DO NOT use in renal failure, hypervolemic
conditions, severe HF, thrombocytopenia, or clotting abnormalities.
Monitor vitals for first 30 mins.
STOP infusion @ first sign of hypersensitivity.
Plasma expander will lower hematocrit and hemoglobin bc of increased
intravascular volume. REPORT a hematocrit below 30% to DR. ASAP
PRIMARY nursing responsibility- MONITOR fluid volume status, both
FVE and FVD.
REPORT ASAP: sings of bleeding, bruising, bloody urine, dark tarry stools,
flushing, SOB, itching (could be hypersensitive), cough, chest congestion,
heart palpatations ( could indicate FVE)
Crystalloids- IV fluids than have electrolytes and other agents that are used
to replace lost fluids and promote urine output. QUICKLY diffuse across
membranes. They leave the plasma and enter the interstitial fluid and ICF.
Infusion of crystalloids will increase total fluid volume, but the compartment
which is most expanded depends on the solute (sodium) concentration.
Hypertonic Crystalloids- draw water from the cells and tissues and expand
plasma volume.
Hypotonic Crystalloids- causes water to move out of plasma into the tissues
and cells.
THESE are NOT considered efficient plasma volume expanders.
Crystalloid IV Solutions:
0.9% NaCl = Normal Saline-Isotonic
Lactated Ringers- Isotonic
D5W- Isotonic also considered hypotonic
3% NaCl= Hypertonic Saline -Hypertonic
5% Dextrose in Normal Saline=D5NS- Hypertonic
5% Dextrose in Lactated Ringers=D5LR- Hypertonic
0.45%NaCl= Hypotonic Saline- Hypotonic
Positively charged electrolytes- cations
Negatively charged electrolytes- anions
Sodium- major electrolyte in the ECF
As sodium levels increase in the body fluid, the osmolality increases,
water will move toward this area.
WHERE SODIUM GOES WATER FOLLOWS = water content of plasma
increases so does blood volume and BP. (important link between water
retention, blood volume and blood pressure)
Hypernatremia- more than 145mEq/L
Most common cause- kidney disease
Other causes- excessive sodium in diet, overtreatment of IV fluids w/sodium
chloride or sodium bicarbonate, inadequate water intake, watery diarrhea,
fever, burns, high doses of glucocorticoids or estrogens.
S&S:
Thirst, fatigue, weakness, muscle twitching, convulsions, weight gain,
dyspnea.
For pt that is Hypovolemic- give hypotonic fluids, D5W or 0.45%NaCl- this
increases plasma volume and reduces plasma osmolality.
Hyponatremia- less than 135mEq/L
Causes: excessive secretion of ADH, Hypotonic IV solutions, Skin, GI and
kidney disorders, burns, GI suction, prolonged fever, diuretic use
Early S&S:
N&V, anorexia, abd cramping
Later S&S:
Confusion, lethargy, convulsions, muscle twitching, tremors, tachycardia,
hypotension, dry skin.
TX: Solutions of Sodium Chloride , Hypertonic salt solutions (3%NaCl)
Nursing Actions: monitor FLUID BALANCE, teach pt signs and symptoms
of FVE during infusion of hypertonic saline solutions and to report it to
nurse ASAP.
S&S of FVE- SOB, palpitations, headache and restlessness.
Potassium- most abundant cation in ICF
Role in regulating intracellular osmolality and maintaining acid-base
balance.
FOR every 1 sodium ion that is reabsorbed, 1 potassium ion is secreted
into the renal tubules.
Hyperkalemia- greater than 5 mEq/L :
Causes: potassium sparing diuretics (Spironolactone), renal dysfunction,
high K+ foods
S&S: Dysrhythmias, heart block, muscle twitching, fatigue, paresthesias,
dyspnea, cramping, diarrhea.
TX: restrict K+ in diet
Temporary fix is Glucose and Insulin
Calcium Gluconate or Calcium Chloride may be given in Emergent situation
to counteract K+ toxicity on the heart.
Sodium Bicarbonate is given to correct acidosis that is concurrent with the
Hyperkalemia.
Polystryrene Sulfonate- give orally or rectally to eliminate K+, give this with
a laxative such as sorbitol.
Hypokalemia- less than 3.5mEq/L:
Causes: loop diuretics (Lasix), strenuous muscular activity , severe vomiting
& diarrhea
S&S:
Muscle weakness, lethargy, anorexia, dysrhythmias, and cardiac arrest.
TX: increase K+ in diet
K+ supplements oral or IV