Chapter 9
Intravenous Access and Fluid Administration
Water is life
Erin Wendt-Hornickle
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, USA
- Q. What are the indications for intravenous catheter placement?
- A. The most common reasons for placing an intravenous (IV) catheter are fluid and drug administration, blood sampling, and emergency preparedness.
Intravascular catheter placement is necessary for IV fluid administration during anesthesia. The American Animal Hospital Association has outlined general guidelines for fluid administration, including recommendations for patients undergoing anesthesia [1]. Fluids given IV help maintain blood pressure, organ perfusion, and normal blood volume.
Intravenous anesthetic induction should be performed via a patent and secure IV catheter. Many induction agents cause adverse effects (tissue damage, pain) when given extravascular; it is important to ensure maintenance of IV access when administering these drugs. Also, having an IV catheter makes giving peri-operative analgesia and antibiotics easier for staff and patients.
Occasionally, blood sampling may be necessary. Though central (jugular) catheters are better suited for this purpose, larger gauge peripheral catheters can be used for obtaining blood samples without repeatedly performing venipuncture on a patient.
Lastly, IV access is an important aspect of emergency preparedness. In the event of a cardiopulmonary arrest, treatment may be administered quickly and seamlessly if an IV catheter is already in place.
- Q. Where can I place a peripheral IV catheter in dogs and cats?
- A. There are many options for IV catheter location in small animal patients. The location is dependent upon many factors, including anesthetist experience, patient demeanor, patient health status or pathology, accessibility of the site, overall goals, and the risk of complications.
The cephalic and accessory cephalic veins on the thoracic limbs are options suitable in most small animal patients. There are several advantages to this location. Thoracic limbs are often easier to keep clean. They are also more accessible for surgical procedures that do not involve the cranial third of the patient. The patency of cephalic and accessory cephalic vein catheters may be easier to maintain due to the straight anatomy and limited motion of that area when compared to other locations. In general, a larger gauge catheter can be placed in a patient’s cephalic vein than in other peripheral sites. There are a few disadvantages to this location. If the patient is aggressive or fractious, maintaining venous access and also ensuring safety of personnel may be difficult. In these instances, restraint for a saphenous catheter may be safer. Also, if the procedure requires access to the patient’s cranial third (e.g., dental prophylaxis, ophthalmic procedures, thoracic limb amputation), this location may not be readily accessible during anesthesia.
Other common choices for intravenous catheter placement include the lateral and medial saphenous veins on the pelvic limbs. Lateral saphenous veins are suitable in most dogs, though they may be more difficult to maintain due to the tortuous nature of the vessel in this area. Medial saphenous veins are suitable in most cats, and are fairly easy to maintain for short periods such as an anesthetic episode. Advantages of catheterization of veins located on the pelvic limb include accessibility if the procedure being performed is on the cranial portion of the patient, and safety of staff if a patient is aggressive or fractious. For fractious patients, an IV extension set filled with saline or heparinized saline can be securely attached to the catheter and then accessed from outside the cage for administration of drugs and so on in the recovery period.
- Q. How do I choose which catheter I should use?
- A. There are several catheter types available for intravenous use. They include winged needle, over-the-needle, through-the-needle, and guide-wire type catheters. The most common type used in peripheral vessels for anesthesia is an over-the-needle type. They are well suited for maintaining peripheral venous access, inexpensive, and very easy to use. Over-the-needle catheters are useful for administering anesthetic drugs and fluids in the perioperative period, but can be maintained and used for fluid administration for 72 h [2].
The gauge of catheter used depends upon the size of the patient. Hansen suggests the following for maintenance therapies in peripheral vessels: for patients less than 5 kg, a 24-20 gauge catheter is appropriate, for patients 5–15 kg, a 22-18 gauge catheter is appropriate and for patients over 15 kg, a 20-18 gauge catheter is appropriate [2].
The main advantage for choosing a larger gauge catheter is less resistance to flow and the ability to deliver large volumes of fluids or drugs over short amounts of time. This may be necessary in patients during anesthesia. Larger catheters will, however, cause more trauma to the vessel. In general, one should choose the smallest gauge catheter that will effectively achieve the goals of intravenous catheterization.
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