Uncommon IV Catheter Sites in Small Animals

Venous access is critical for patient care in veterinary medicine because it provides a route for administration of fluids, medications, and blood products as well as a source of blood for sampling. The most common “go to” site for intravenous (IV) access in small animal patients is the cephalic vein. However, what happens if this vein is not accessible? Why might we need to choose another IV access site, and what other sites can we choose from? This article discusses sites other than the cephalic vein that can be used for IV catheter placement in small animals (TABLE 1).

General Indications for Using Alternative IV Catheter Sites

Many factors affect the size and accessibility of blood vessels (BOX 1). For example, patients experiencing hypotension, hypothermia, or both will experience vasoconstriction. Neonates and exotic small mammal pets often have extremely small vessels, making it difficult to gain IV access.¹ Physical restrictions to venous access include masses (e.g., lipomas, mast cell tumors, skin tags), skin infections, and edema at the site. Other challenges to IV access include changes to an animal’s conformation, such as angular limb deformities or amputated limbs. Certain catheterization locations may be selected over others to reduce bleeding around insertion sites in patients with thrombocytopenia or other clotting disorders. The number of IV access sites will also be decreased by limb trauma (e.g., fractures, open wounds).

Other considerations include the patient’s mobility and potential for chewing or scratching out the catheter; the potential of catheter soiling by frequent diarrhea, urination, or urinary incontinence; and the overall stress during patient restraint for catheter placement in a particular area. Medications themselves can cause phlebitis, which should lead to consideration of other IV catheter options for patients that could potentially receive high concentrations of potassium chloride (KCl) (80 mEq/L or higher), dextrose (7% or higher), mannitol, or chemotherapy agents. 

General Catheter Placement and Maintenance

Sterile placement of IV catheters is essential. Hands should be appropriately washed, exam gloves or sterile gloves (location dependent) should be worn, and aseptic technique should be followed. To ensure the site can be as clean and secure as possible and to prevent discomfort during tape removal, the location should be clipped approximately 2 inches above and below where the catheter will be placed and all the way around on peripheral limbs. The site should be cleaned with sterile 0.9% sodium chloride (normal saline) combined with chlorhexidine scrub to form a 0.5% to 2% concentration.^2,3 After placement, the catheter should be flushed with sterile saline to confirm patency and then secured with sterile bandage material.³ All catheters, regardless of location, should be rewrapped daily and the insertion site should be evaluated twice daily for signs of dislodgement, swelling, infection (red or yellow discolored skin around insertion site or purulent discharge), or pain and tenderness.^2,3 For lower limb catheters, the nail and tip of the third and fourth digits should remain visible outside of the bandage to enable monitoring for signs of swelling. Elizabethan collars will prevent licking or chewing at the site. The bandage material should be routinely inspected to ensure that it is dry and free from water, food, urine, or fecal matter. Catheters that are not being used for continuous IV fluids should be kept patent by flushing with normal saline every 2 to 4 hours.^2-4

Alternative Sites

Jugular Vein IV

Location: The left and right external jugular veins are located on the ventrolateral aspects of the neck, off the midline on either side of the trachea (FIGURE 1A).⁵ On each side, the jugular vein branches into the subclavian vein which runs into the cranial vena cava.⁵ The jugular veins lay superficial to the brachiocephalicus, sternocephalicus, and sternothyroideus muscles and are innervated by cranial nerve XI (accessory nerve) and the segmental nerves.⁵

Indications: When used as a central line, a jugular catheter is a large-bore catheter that is placed in the jugular vein.^4,6 It can be a regular 1-port catheter or a multiport catheter that enables use of up to 3 ports at the same time. The choice of which type to use is based on access to supplies and whether multiple fluids will be administered or blood samples collected.⁶

Placement/maintenance: To reduce the risk for infection, the catheter location should be prepared as aseptically as possible.^4,6,7 After catheter placement, bandaging above and below the insertion site will help maintain sterility and protect the catheter from becoming dislodged. Jugular catheters should be sutured in place to prolong their longevity and maintain proper placement. The catheter should be sutured at the base, the top, and both sides of the butterfly tab. If a patient is being monitored for central venous pressure, the catheter should be measured to the third to fifth rib space to ensure that the tip of the catheter sits just cranial to the right atrium.⁷ A single lateral thoracic radiograph should be taken to confirm that the catheter has not been advanced into the heart (FIGURE 1B).⁷ Otherwise, the anatomic location of the central line is not as concerning as long as blood samples can be obtained.⁷ If the catheter is a standard peripheral 18-gauge to 22-gauge catheter, then no placement radiograph is needed.

Accessory Cephalic Vein IV

Location (FIGURE 2): The accessory cephalic vein branches off the cephalic vein at the proximomedial aspect of the carpus. It is located on the anterior aspect of the metacarpus and makes a “Y” shape as it passes over the carpus.⁵ The accessory cephalic vein is superficial to the extensor carpi radialis, superficial digital flexor, and flexor carpi radialis muscles.⁵ Innervating these muscles are the distal radial, median, and ulnar nerves.⁵ The location of this vein often makes it easier to see than the cephalic vein.

Indications: Indications for using this vein include ease of access due to its prominence, restrictions on the proximal aspect of the limb (e.g., masses, edema, scar tissue), or need to avoid use of back limbs because they cannot be kept clean and dry.

Placement/maintenance: After catheter placement, be sure to have good padding under the hub of the catheter. For bandages that cover the entire paw to the digits, the nail and tip of the third and fourth digits should remain visible for monitoring. Due to the location of the accessory cephalic vein, the catheter will extend medially. When this vein is used, be sure that other veterinary staff members are aware so that they do not mistake the catheter for a cephalic vein catheter that is twisted sideways and needs to be adjusted.

Auricular Vein IV

Location: The auricular veins are located on the rostral (medial auricular vein) and caudal (lateral auricular vein) edges of the ear.⁵ These veins are located beside the rostral and caudal auricular nerves, which branch into the auriculopalpebral and facial nerves.⁵

Indications/contraindications: This location can be used for anesthetized patients when catheter sites under drapes are inaccessible or no longer functioning or for patients that have large ears (e.g., basset hounds, mastiffs, Great Danes, dachshunds, Doberman pinschers, rabbits).^8,9 Vasoconstriction renders an auricular vein a poor choice for patients with hypothermia or insufficient perfusion. Auricular veins are extremely superficial, and care should be taken not to puncture through the pinna.

Placement/maintenance (FIGURE 3): Auricular vein catheters can be difficult to secure in place and should not be considered the first choice for a patient that needs significant volumes of fluid. In general, make sure the catheter is secured well to the ear with tape. Suturing the tape to the ear may provide more stability, especially for a patient likely to shake its head. The integrity of the catheter can be maintained by making a splint for the ear with a small cup or tongue depressor. If the patient has to wear an Elizabethan collar, close monitoring is needed to ensure that the collar does not rub against the ear and dislodge the catheter.

Lateral Saphenous Vein IV

Location (FIGURE 4): The lateral saphenous vein runs over the lateral aspect of the distal tibia, just proximal to the tibiotarsal joint (hock) and superficial to the superficial digital flexor, long digital flexor, and gastrocnemius muscles.⁵ Innervating the muscles surrounding this vein are the tibial and peroneal nerves.⁵ In dogs, this vein is larger in diameter than the medial saphenous vein.⁸

Indications: The lateral saphenous vein can be used for a regular peripheral catheter or as the introduction site for a peripherally inserted central catheter (PICC line).⁶ A PICC line is a long, large-bore catheter, 18-gauge or larger, with single or multiple lumens. It can be inserted into the vein to help deliver larger quantities of fluids, peripheral parenteral nutrition, or multiple medications through multiple ports (the extra lumen ports keep the medications separate).^8,10 PICC lines can help maintain the longevity and integrity of the vein.⁸ In a study performed in 2008, PICC lines successfully remained in patients for an average of 16.2 days.¹⁰ No complications (e.g., venous thrombosis, sepsis, extravasation) were noted during the duration of the catheterization. Bandaging the catheter after placement can be difficult due to the proximity of the tibiotarsal joint. For a regular peripheral catheter, the tape should be tight enough to keep the catheter in place yet should give the skin, muscles, and tendons enough room to fluctuate in size after fluid resuscitation. Taping too tightly can lead to swelling of the paw and digits. The chance of swelling can be minimized by starting the bandaging at the distal aspect of the paw and proceeding proximally. The third and fourth digits should remain exposed for monitoring. Bandaging should extend proximal to the catheter insertion site (usually proximal tibia).

Medial Saphenous Vein IV

Location (FIGURE 5): The medial saphenous vein is located on the mid-to-distal aspect of the proximal femur, superficial to the gracilis and sartorius muscles.⁵ The nerves surrounding this vein are the femoral nerve and its distal branch (saphenous nerve).⁵ 

Indications: The medial saphenous vein is a good catheter location for patients that are nonambulatory and have no other patent or accessible veins. In cats, the medial saphenous vein is larger and more easily catheterized than the lateral saphenous vein.⁸

Placement/maintenance: For placement of this catheter, the patient should be lying on the same side as the desired vessel (i.e., in right lateral recumbency for access to the right medial saphenous vein), and the person restraining the patient should hold the contralateral pelvic limb in abduction. After catheter placement, tape should be placed around the hub of the catheter and wrapped all the way around the patient’s thigh. Care should be taken to keep the tape loose enough to prevent swelling of the distal limb. Padding (e.g., towels) can be placed between the patient’s legs to prevent compression of the catheterized limb, which can cause swelling or edema around the catheter site. If the patient is too mobile, the catheter could easily become dislodged.

Common Dorsal Digital Vein (Dorsal Pedal Vein) IV

Location (FIGURE 6): The dorsal pedal vein is located on the dorsal aspect of the paw, superficial to the long digital extensor muscle and the extensor retinaculum. It is innervated by the common fibular nerve.⁵ The vein begins to branch into a “Y” shape at the middle of the metatarsal bones; either the left or right branch can be used.⁵ Lack of excess fat or skin over the area often makes this vein more visible than most.

Placement/maintenance: After the catheter is inserted, tape should be placed around the hub to secure it to the paw. When bandaging the catheter, start from the distal aspect of the limb and extend the bandage proximally to the tibiotarsal joint or above for extra security.

Sublingual Vein IV

Location (FIGURE 7): The sublingual vein begins on the rostral portion of the tongue and runs caudally to the mylohyoid muscle.⁵

Indications: The sublingual vein can be used for a short time in anesthetized patients. If peripheral IV access has been lost while an animal is anesthetized, catheterization of the sublingual vein can be attempted as the tongue is often still readily accessible. A sublingual catheter is typically used to give IV medications to maintain anesthesia until a new peripheral catheter can be placed.

Placement/maintenance: When placing a sublingual catheter, first clean the tongue as aseptically as possible with chlorhexidine solution and saline (0.13% solution). However, before cleaning, ensure that the endotracheal tube cuff is inflated to avoid passage of chlorhexidine cleaning solution or fluids into the trachea. After cleaning the catheter site, rinse the mouth with sterile water or normal saline to avoid the caustic effects of long-term exposure to chlorhexidine on the tongue. Tongue depressors can be used to make a splint to add rigidity to the tongue and make it easier to hold the catheter in place. 

Corpus Cavernosum IV

Location (FIGURE 8): The corpus cavernosum consists of 2 columns of spongy tissue in the shaft of the penis.⁵ This tissue is filled with blood vessels that become enlarged during erection.⁵ The corpus cavernosum is located on the lateral aspect of the penis caudal to the os penis.⁵

Indications: Although not used extensively, corpus cavernosum catheterization is a short-term option for administering resuscitation fluids or medications until another route of IV access is achieved.^11,12 Experimental models have shown that catheters placed in the corpus cavernosum can support sufficient flow rates to resuscitate hypovolemic animals and can be used to administer cardiac arrest drugs (e.g., epinephrine, atropine).¹¹ Although administration of other emergency drugs via this route has not been studied, no complications have been reported after delivery of blood products and IV phenobarbital to some patients via the corpus cavernosum.¹²

Placement/maintenance: A large-bore catheter (18-gauge or 19-gauge) is inserted on the lateral aspect of the penile skin at a 45° angle caudal to the os penis toward the corpus cavernosum.¹² The catheter can be taped and sutured to the dorsal aspect of the shaft of the penis.

Umbilical Vein IV

Location: The umbilical vein is located on the umbilicus of neonates.

Indications/contraindications: The umbilical vein can be accessed immediately after birth as long as the vein was not ligated after a cesarean delivery.¹² Because the umbilicus begins to dry and harden and falls off within 24 to 72 hours after birth, this vein may no longer be a viable choice after 24 hours.

Placement/maintenance: Accessing this vein can be difficult and time consuming if not practiced regularly; thus, a better choice for IV access in a neonate may be an intraosseous catheter. For access to the umbilical vein, the base of the umbilicus should be surrounded with umbilical tape that is tightened enough to prevent hemorrhage.¹² To prevent infection and possible sepsis in the neonate, sterility of site preparation should be similar to that for a central line or PICC line.¹² The catheter should not be advanced more than a few centimeters beyond where the flash of blood occurs. Advancing farther could result in the catheter being inserted into the portal venous system. A radiograph should be taken to check appropriate placement.¹² 

Intraosseous IV

Location (FIGURE 9): The 3 most common locations for intraosseous catheter placement are the medullary cavities of the greater tubercle of the proximal humerus, the intertrochanteric fossa of the proximal femur, and the tibial tuberosity.^12-14 Other locations include the wing of the ilium and ischium in small mammals and distal ulna and proximal tibia in birds.^1,12,13

Indications/contraindications: Intraosseous catheters can be used when a venous catheter cannot be placed. Most medications that can be administered IV can also be delivered via the intraosseous route.¹² The exceptions are drugs that are toxic to bone marrow (e.g., sodium bicarbonate, chemotherapy agents, large amounts of hypertonic saline).^12,13 If the catheter was advanced into the spongy portion of the bone that has a network of blood vessels and capillaries, blood can be sampled from an intraosseous catheter.¹⁵ In a study of 12 dogs that compared 0.5 mL of blood collected from the jugular vein versus from the proximal tibia, samples were tested for blood urea nitrogen (BUN), glucose, packed cell volume (PCV), total plasma protein, lactate, potassium, sodium, and chloride. The authors found statistically significant differences between blood collected at the 2 sites for BUN, potassium, sodium, and chloride and a large but not statistically significant difference for PCV.¹⁵ However, it was determined that the differences were not clinically significant and blood from an intraosseous catheter could be used as a method for assessing parameters, excluding potassium and PCV, in healthy dogs. Further studies need to be performed in critically ill patients to determine if this route is reliable for other blood values.   

Placement/maintenance: Because placement of any intraosseous catheter involves going through the superficial and underlying tissues and muscle, there is always a risk for muscle trauma and nerve damage. For example, the intertrochanteric fossa of the proximal femur is adjacent to the sciatic nerve, which innervates the biceps femoris muscle (among others).⁵ Other muscles and associated nerves that could be affected during placement of intraosseous catheters include the brachiocephalicus muscle/spinal accessory nerve for the proximal humerus, gluteal muscles/caudal or cranial gluteal nerve for the intertrochanteric fossa of the femur, and quadricep muscles/femoral nerve for the proximal femur.⁵ Two-view radiographs can confirm appropriate placement (FIGURE 10).

As with all catheters, intraosseous catheter placement should be sterile. For traumatized limbs, fractures should be ruled out before placing an intraosseous catheter as any fluid or medication injected through the catheter could extravasate outside the bone into the surrounding muscle and tissue.¹³ Patients that are not ideal candidates for intraosseous catheters are those with diseases or conditions that make a bone easily prone to fracture (e.g., osteosarcoma; malnutrition; incomplete bony development due to young age; loss of calcium and phosphorus with resulting decreases in bone density, as in geriatric patients).¹⁶ 

Summary

For veterinary nurses, being prepared for the unexpected should be considered part of the normal day. When cephalic veins are not available for any reason, veterinary nurses need to have a backup plan for alternative routes of venous access. Knowing the correct anatomic locations of individual vessels, including bony landmarks as well as underlying muscles and nerves, is crucial for proper placement of the catheter and for minimizing catheter-associated trauma. Of the many options for gaining IV access, the option chosen should be the one that best fits that patient’s condition and needs.

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Editor’s Note: A previous version of this article erroneously referred to the ilium as the ileum. In addition, the Figure 10 caption misidentified the proximal humerus. These have been corrected; we regret the error.