Large Volume Parenteral (LVP) Solutions
Parenteral solutions are packaged as large volume parenteral (LVP) solutions
and small volume parenteral (SVP) solutions. LVP solutions are typically bags
or bottles containing larger volumes of intravenous solutions. Common uses of
LVP solutions without additives include: 1) correction of electrolyte and fluid
balance disturbances; 2) nutrition; and 3) vehicle for administering other drugs.
Large volume parenteral solutions are packaged in containers holding 100 ml
or more. There are three types of containers: glass bottle with an air vent
tube, glass bottle without an air vent tube, and plastic bags.
Plastic bags have advantages over glass bottles: they do not break; they weigh
less; they take up less storage space, and they take up much less disposal space.
However, some drugs adsorb to the plastic. Also, some drugs and solutions leach
a plasticizer out of the plastic; the plasticizer is included to keep the plastic
pliable. There are now newer plastics that minimize some of these problems.
Plastic bags are available in different sizes. The most common sizes are 250,
500, and 1,000 ml. The top of the bag has a flap with a hole in it to hang the
bag on an administration pole. Graduation marks are on the front of the bag
to indicate the volume of solution used. They are marked at 25 ml to 100 ml
intervals depending on the overall size of the bag. The plastic bag system collapses
as the solution is administered so a vacuum is not created inside the bag.
At one end of the bag are two ports of about the same length. One is the administration
set port and the other is the medication
port. The administration set port has a plastic cover on it
to maintain the sterility of the bag; the cover is easily removed. Solution
will not drip out of the bag through this port because of a plastic diaphragm
about ½ inch inside the port. When the spike of the administration set
is inserted into the port, the diaphragm is punctured, and the solution will
flow out of the bag into the administration set. This inner diaphragm cannot
be resealed once it is punctured. The medication port is also covered by a protective
rubber tip. Drugs are added to the solution through this port using a needle
and syringe. There is an inner plastic diaphragm about ½ inch inside
the port, just like the administration set port. This inner diaphragm is also
not self-sealing when punctured by a needle, but the protective rubber tip prevents
solutions from leaking from the bag once the diaphragm is punctured.
Because of the advantages of plastic bags, glass LVP solution bottles are not
often used. The major advantage of glass bottles is to administer drugs that
are incompatible with plastic bags. Glass intravenous bottles are packaged with
a vacuum, sealed with a solid rubber closure, and the closure is held in place
by an aluminum band. Graduation marks are along the sides of the bottle and
are usually spaced every 20 ml to 50 ml. The solution bottle is hung on an administration
pole in an inverted position using the aluminum or plastic band on the bottom
of the bottle.
Solutions in either the plastic bag or glass bottle flow from the containers
to the patient through an administration set. But for solutions to flow out
of a glass container, air must be able to enter the container to relieve the
vacuum as the solution leaves. Some bottles have air tubes built into the rubber
closure for this purpose. Some bottles do not, in which case an administration
set with a filtered airway in the spike must be used.
Many different LVP solutions are commercially available. Four solutions are
commonly used either as primary fluids (infused at 2 - 3 ml per minute) or as
the base of an admixture solution. The solutions are sodium chloride solution,
dextrose solution, Ringer's solution, and Lactated Ringer's solution. Various
combinations of different strengths of sodium chloride and dextrose solutions
are also available, i.e., 5% dextrose and 0.45% sodium chloride, or 5% dextrose
and 0.2% sodium chloride.