Grown Up...
©
A Newsletter For Those Who Care For
ADOLESCENTS, ADULTS, and AGING ADULTS
TYPES OF IV SOLUTIONS… IMPLICATIONS
Volume 17, Issue 11
November 2012
Editor-in-Chief: Mary Myers Dunlap, MAEd, RN
BEHAVIORAL OBJECTIVES
AFTER
READING THIS NEWSLETTER THE
LEARNER WILL BE ABLE TO:
1. Describe fluid compartments within the human body.
2. Discuss how various crystalloid solutions affect fluid
distribution.
Maintaining a balance of fluid volume and electrolytes is
essential to health. Crystalloid intravenous solutions are
routinely administered peripherally for fluid maintenance, as
well as for correcting fluid and electrolyte imbalances. The
major component of a crystalloid IV solution is sterile water.
Chemically, water is referred to as a solvent. A solvent is a
substance that dissolves other materials, called solutes. For
example, when making a cup of instant coffee, the water is
the solvent and the instant coffee is the solute. In the body,
the solutes include electrolytes, oxygen, carbon dioxide,
glucose, urea, amino acids, and proteins.
Crystalloid solutions come in different forms - isotonic,
hypotonic, and hypertonic, and have different impacts on the
body. Each has a specific purpose and is prescribed based
on the patient’s needs. It is important for healthcare
professionals to have an understanding of the different types
of crystalloid IV fluids, along with their indications for use.
This newsletter will discuss fluid compartments within the
body, and osmosis, which affects distribution of fluids.
Examples of crystalloid IV solutions will be described,
including implications for the healthcare provider.
TOTAL BODY WATER
Water is the largest single component of the body. The
percentage of total body water (TBW) is influenced by age,
gender, and body mass. The proportion of TBW decreases
with aging. Infants have the highest proportion of water,
accounting for 70% - 80% of their weight. The TBW for
adults is approximately 60%, compared to 40% in the
elderly. Muscle tissue contains more water than the same
amount of adipose tissue. Fat tissue is essentially free of
water. Therefore, regardless of age, water makes up a
greater percentage of a lean person’s body weight than an
obese person’s. Women naturally have proportionately
more body fat than men, and, therefore, have a lower
percentage of body fluid. Likewise, in the elderly, as
muscular tissue diminishes, so does the percentage of bodily
fluids.
A patient’s TBW in liters can easily be calculated using
the formula: TBW in liters = % TBW x body weight in
kilograms. Conveniently, one liter of fluid weighs one
kilogram, Therefore, an adult patient who weighs 70 kg (70
kg x 60% [0.6]) = 41 kg, which means the patient’s volume of
TBW is 41 L.
FLUID COMPARTMENTS
Fluids within the body are contained in two basic
compartments - intracellular and extracellular. Intracellular
fluid (ICF) consists of fluid contained within all body cells and
is the larger of the two compartments. ICF makes up
approximately 2/3rds of the TBW and is vital to normal cell
functioning, such as cellular growth and repair. It also
carries nutrients and oxygen to the cells and wastes and
carbon dioxide from the cells.
The extracellular fluid (ECF) compartment contains all
the fluids outside the cells. It is the smaller of the two main
fluid compartments, containing the remaining 1/3 of body
fluid. ECF is the transport system that carries nutrients to
and waste products from the cells.
A mnemonic to help remember which fluid compartment
contains 1/3rd and which 2/3rds of the TBW:
E comes before I in the alphabet, so E (ECF) is 1/3 and
I (ICF) is 2/3
The ECF is divided into two major areas, interstitial and
intravascular. Interstitial fluid fills the spaces between the
tissues. The fluid in this area would be increased in a patient
who has generalized edema. Intravascular fluid is the
plasma, the liquid portion of the blood. In order to
understand fluid balance, it’s important to remember peripheral IV solutions go directly into the intravascular area
of the ECF.
For example, if a patient has generalized edema, which
may be caused by cardiac, renal, or liver disease, there is
excessive accumulation of fluid in the interstitial spaces.
Transcellular fluid (fluids contained in body spaces), such as
cerebrospinal fluid, the pleural cavity, and joint spaces
(synovial fluid), is usually not calculated as a percentage of
the ECF. It is minimal, 2.5% of the TBW. Interstitial fluid
accounts for close to 80% of ECF in adults, and
intravascular fluid, about 20%. In the previous example of
the patient having 41 L of TBW, 27 L of fluid is located in the
tissue fluid (2/3 x 41L = 27L) and 14 L in the blood plasma
(1/3 x 41 = 14L).
ELECTROLYTES: Each fluid compartment of the body has a
distinctive pattern of electrolytes. Sodium (Na+) and chloride
(Cl-) are the major electrolytes in ECF.
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In intracellular fluid, potassium (K+) and phosphate (P04-),
are the major electrolytes. In both compartments, other
electrolytes, are also present, but in much smaller quantities.
DISTRIBUTION OF FLUIDS:
Water is in a constant state of motion in the body, in an
effort to maintain balance of water and electrolytes between
the ICF and ECF compartments, as well between the
intravascular and interstitial fluid. Fluid compartments are
separated by semi (or selectively) permeable membranes,
such as capillary and cell membranes. Such membranes
allow water to easily flow into and out of these fluid
compartments in an effort to equalize the number of solutes
in each. Large molecule solutes can’t cross semi- permeable
membranes to maintain homeostasis, hence, the name
“semi” permeable. It is up to the water to shift.
OSMOSIS
In the left image, the concentration of sugar
molecules is greater on the right side of the
membrane than on the left. The water molecules
are small enough to move across the semipermeable membrane, but the larger sugar
molecules cannot pass through.
On the right image, the water molecules moved
across the membrane until the water and sugar
molecules are of equal concentration on both sides.
This lowers the water level on the left side and
raises it on the right side.
Water tends to move across the membranes until the
solute concentration on both sides is the same. Water
moves from the side that has a lower concentration of
solutes, to the side that has a higher level, in an effort to
equalize them. Movement of water stops when each side of
the membrane becomes equal in its concentration of solutes.
This is known as osmosis and is a common mechanism the
body uses to maintain homeostasis.
CRYSTALLOID IV SOLUTIONS
Crystalloid solutions contain sterile water and small
molecules that flow easily across semipermeable
membranes, allowing transfer between the fluid
compartments. The small molecules may be electrolytes or
nonelectrolytes, such as dextrose. Crystalloid solutions
come in many preparations and are classified according to
their tonicity or osmolality - the ability to cause water
movement from one fluid compartment to another.
Each IV solution has a specific purpose and the specific
IV solution is ordered based on the patient’s needs. The
concentration of solutes in the IV solution, will determine the
need for movement of body water and the direction of the
change to produce balance.
Isotonic solutions – do not draw or push fluid into the cell
Hypotonic solutions - push fluid into the cell
Hypertonic solutions – draw fluid out of the cell and into
the extracellular space.
Isotonic: When the IV solution contains the same amount of
solutes as body fluid, it is referred to as an isotonic solution,
and no fluid shift, osmosis, occurs. Isotonic solutions are
generally used to treat patients with fluid loss. Common
examples of isotonic solutions are 0.9% sodium chloride
(NaCl), Lactated Ringers (LR) and D5W. NaCl is commonly
used as a volume expander in patients with a fluid deficit and
in conjunction with blood transfusions. LR is used to treat
sudden blood loss, dehydration, and burns. Patients with
renal failure should not receive Lactated Ringer's solution
because it contains potassium and could lead to potassium
overload (hyperkalemia.) D5W (5% dextrose in water) is also
considered an isotonic solution, but can also be categorized
as a hypotonic solution. When D5W is initially infused, it is an
isotonic solution, but when the dextrose is metabolized, the
solution actually becomes hypotonic, causing fluid to shift
into cells. D5W is not indicated for patients with renal failure
or cardiac problems since it can cause fluid overload. Also,
patients at risk for intracranial pressure should not receive
D5W since it could increase cerebral edema.
Hypotonic: When a crystalloid solution contains fewer
solutes than the body fluid, it is less concentrated and is
referred to as hypotonic. Hypotonic fluids are used to treat
patients when fluids need to be shifted back into the cell,
such as may occur in patients with diabetic ketoacidosis, in
which high serum glucose levels draw fluid out of the cells.
Hypotonic fluids can be dangerous because of the sudden
shift of fluid from the intravascular spaces to the cells. The
decrease in vascular volume can cause fluid deficit,
hypotension, and cardiovascular collapse. Hypotonic
solutions should not be administered to patients who are at
risk for increased intracranial pressure because of a
potential fluid shift to the brain tissue, which can cause or
exacerbate cerebral edema. In addition, hypotonic solutions
are not appropriate for patients with liver disease, trauma, or
burns due to the potential for depletion of intravascular fluid
volume.
Hypertonic Solutions: If a crystalloid solution contains more
solutes, such as electrolytes, than the body fluid, it is more
concentrated and is referred to as hypertonic. Hypertonic
solutions cause water to leave the cells in order to dilute the
solute. An example of a hypertonic crystalloid solution is 3%
sodium chloride. Hypertonic solutions should be given slowly
to avoid intravascular fluid volume overload and pulmonary
edema. During infusion, serum electrolytes should be
assessed, as well as signs and
symptoms of fluid overload. It is important for healthcare
professionals to have an
understanding of the different types of
crystalloid IV fluids, along with their
indications for use.
Growing Up With Us, Inc.
PO Box 481810 • Charlotte, NC • 28269
GUWU Testing Center
www.growingupwithus.com/quiztaker/
Phone: (919) 489-1238 Fax: (919) 321-0789
Editor-in-Chief: Mary M. Dunlap MAEd, RN
E-mail: [email protected]
Website: www.growingupwithus.com
Copyright © 2012 Growing Up With Us, Inc. All rights reserved.
Page 2 of 4
Name:_____________________________________________________
Date:___________________________________
Employee ID#:____________________________________________
Unit:____________________________________
POPULATION/AGE-SPECIFIC EDUCATION POST TEST
GROWN UP... Caring For Adolescents, Adults, and Aging Adults November 2012 Competency: Demonstrates Age-Specific Competency by correctly answering 9 out of
10 questions related to Types of IV Solutions… Implications.
TYPES OF IV SOLUTIONS… IMPLICATIONS
1. What percentage of an adult’s body weight is typically fluid?
a.
b.
c.
d.
20
40
60
80
2. The ECF compartment contains 2/3rds of the TBW.
a. True
b. False
3. Changes in the level of solute concentration, as occurs in various types of IV solutions, influence
the movement of fluid and electrolytes between the fluid compartments.
a. True
b. False
4. Generalized edema is excess accumulation of fluid in which compartment?
a.
b.
c.
d.
Intracellular
Extracellular
Intravascular
Interstitial
5. What is the primary means of water movement between intracellular and extracellular fluid?
a.
b.
c.
d.
Diffusion
Osmosis
Filtration
Reabsorption
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Name:_____________________________________________________ Date:___________________________________
POPULATION/AGE-SPECIFIC EDUCATION POST TEST
Employee ID#:____________________________________________ Unit:____________________________________
GROWN UP... Caring For Adolescents, Adults, and Aging Adults TYPES OF IV SOLUTIONS… IMPLICATIONS
6. All fluids inside the cells are referred to as what type of fluid?
a.
b.
c.
d.
intracellular
extravascular
intravascular
interstitital
7. Which isotonic fluid is used to administer blood products?
a.
b.
c.
d.
0.9% sodium chloride
LR
D5W
Ringer’s solution
8. Isotonic IV fluids increase:
a.
b.
c.
d.
osmosis.
active transport.
intracellular volume.
intravascular volume.
9. Which type of solution can be used to shift fluids into the cells?
a.
b.
c.
d.
Isotonic
Hypotonic
Hypertonic
Crystalloid
10. In the body, water tends to move across semi-permeable membranes between the fluid
compartments until the solute concentration is the same on both sides.
a. True
b. False
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