a. Crystalloid Solutions. Crystalloid solutions contain small molecules that
pass freely through cell membranes and vascular system walls. These solutions are
useful as fluid expanders and are stored at room temperature. The crystalloid solutions
are a useful source for electrolytes and a temporary source of fluid volume. They flow
out of the vascular system rather quickly. Lactated Ringer's is an example of a
b. Colloid Solutions. The colloid solution contains molecules that are
frequently very complex and much larger than those in the crystalloid solutions. A
solution that contains protein is colloidal. The colloidal solutions are needed when a
solution is required to remain in the vascular system. Colloid solutions generally require
refrigeration and can be stored for a limited period. Whole human blood U.S.P. and
Hetastarch are examples of colloid solutions.
2-10. NORMAL FLUID LOSS
As mentioned earlier, there are four ways the normal healthy body loses fluids
daily. People are generally unaware of the loss of fluids since the body does an
excellent job of replacing the lost amounts of fluid and electrolytes. It is only when there
is a severe loss during illness or injury that the body has difficulty replacing these
a. Perspiration. Perspiration is a constant route for fluid loss. About 650
milliliters of perspiration are lost during a normal day by a healthy person. Along with
water, a liter of perspiration has about 45 mEq of sodium, 4.5 mEq of potassium and
57.5 mEq of chloride. A normal person only becomes aware of the perspiration loss
during very strenuous exercise or when the day is very hot. As a general rule, where
sodium goes, water follows. That is why there is always sodium on the skin following
b. Respiration. Respiration occurs around-the-clock, but most people are not
aware that they are exhaling fluid in the form of water vapor every time they breathe.
We become aware of the vapor loss during cold weather when the vapor can be seen
as it is exposed to low temperatures. About 450 milliliters of fluid are lost during a
twenty-four hour period by respiration.
c. Feces. A small amount of fluid is normally contained in the feces. About 100
milliliters of fluid are lost in this manner during a day.
d. Urine. Urination accounts for the greatest fluid loss daily. About 1300
milliliters of urine are excreted by the normal person each day.
e. Total. If these four loss routes are totaled, we find that about 2500 milliliters
of fluid are lost and must be replaced daily. See figure 2-7 for a summary.