osmolar. Hypo-osmolar might be caused by a fluid deficit. Hyper-osmolar might
be caused by fluid excess.
The concentration of solutes is important when determining the proper
replacement fluid for a patient whose fluids and electrolytes are imbalanced.
Replacement fluids are replaced orally (by mouth or nasogastric tube) or par-
enterally with IV fluids (intravenously or subcutaneously).IV Fluids
The osmolality of many IV fluids is similar to serum osmolality, which is
290 mOsm/kg H 2 O. IV fluids are:- Isotonic.This is in the iso-osmolar range (240 to 340 mOsm/L) where
the concentration of the IV fluid is the same as concentration of intracellu-
lar fluid (NaCl 0.9%, normal saline). - Hypotonic.This is in the hypo-osmolar range (< 240 mOsm/L) where
the concentration of the IV fluid is less than the concentration of intracel-
lular fluid (NaCl 0.45%, sodium chloride). - Hypertonic.This is in the hyper-osmolar range (> 340 mOsm/L) where the
concentration of the IV fluid is more than the concentration of intracellu-
lar fluid (Dextrose 5% in 0.45% saline).
IV solutions are classified as crystalloids, colloids, or lipids.CRYSTALLOIDS
Crystalloids are used for replacement and maintenance of fluid balance therapy.
These include dextrose, saline, and lactated Ringer’s solution.COLLOIDS
Colloids are volume expanders that increase the patient’s fluid volume. These
include Dextran, amino acids, hetastarch, and plasmanate.- Dextran is not a substitute for whole blood because it does not have com-
ponents that carry oxygen. Dextran 40 tends to interfere with platelet func-
tion resulting in prolonged bleeding times.
(^160) CHAPTER 10 Fluid and Electrolyte Therapy