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Fluid Therapy

Teresa Rieser, DVM, DACVECC

Veterinary Specialty Care, Mt. Pleasant, SC, USA

Intravenous fluids are a commonly used treatment in diameter allows for rapid bolusing of fluids. This type of
small animal medicine. A full understanding of the indi- catheter is usually secured in place with medical tape.
cations and potential fluid choices allows clinicians to Through‐the‐needle catheters are also widely availa-
reap the maximum benefit from fluid therapy while min- ble. This type of catheter tends to be greater in length
imizing possible complications. and is used when central venous access is desired for
repeated blood sampling or the administration of a
Vascular Access hyperosmolar solution such as total parenteral nutrition.
Catheters placed using a guide wire can be single lumen
or multilumen and are placed into a central vein. This
Catheter Types
type of catheter allows for blood sampling, fluid admin-
Fluid therapy can be administered via a number of differ- istration, including the concurrent administration of
ent routes, including intravenous, subcutaneous, and noncompatible fluids through separate lumens, as well
intraosseous. In order to administer fluids intravenously, as the administration of hyperosmolar solutions that
venous access must first be established. Most commonly, would cause significant phlebitis if administered periph-
this involves the placement of a catheter within a periph- erally. Placement of a central venous catheter also allows
eral vein or within the jugular vein. There are a variety of for monitoring of central venous pressure in patients to
catheter types currently available, including winged nee- guide fluid therapy.
dle (butterfly catheters), over the needle, through the Intravenous catheters may be made of a number of dif-
needle and catheters that are placed using a guide wire. ferent materials, including polyurethane, Teflon®, and
When placing an intravenous catheter, a number of silicon elastomer (silastic). Polyurethane and Teflon
questions should be considered to ensure the most catheters are most commonly used, as they are cost‐
appropriate catheter is selected. effective and relatively easy to insert. Silicon elastomer
Butterfly‐type catheters are rigid needles with a plastic (Silastic®) catheters are very flexible and less likely to
“butterfly” at the needle hub to make handling easier. result in catheter‐related thrombophlebitis but they are
The needles are then attached to a length of tubing that more expensive and technically challenging to place.
can be connected to a syringe for bolus drug delivery or Silastic catheters are used for long‐term catheterization,
blood sample collection. This type of catheter is useful while Teflon or polyurethane catheters are reasonable
for instances where the catheter does not need to be choices for shorter term catheterization.
maintained within the vein. An example would be an IV The placement of intravenous catheters is common in
bolus injection of medication or a single episode of veni- small animal veterinary medicine. Peripheral catheters
puncture to collect blood samples. are most commonly placed in the cephalic, medial or lat-
If a catheter needs to be maintained within a peripheral eral saphenous or femoral vein. In some animals, the
vein for any duration of time then an over‐the‐needle veins of the ear can also be used for catheterization.
type catheter is most commonly used. Theses catheters Central catheters are placed within the jugular vein or
are relatively easy to place and can be maintained within threaded from a peripheral vein into the vena cava. In
a vessel for a number of days with diligent nursing care. If order to preserve the integrity of the catheter and mini-
placed in the critically ill, emergent or surgical patient, mize discomfort and inflammation, catheters should not
the short length of the catheter coupled with a reasonable cross a joint. Common sense would also dictate that the

Clinical Small Animal Internal Medicine Volume I, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical