Catheters in Reptiles

Video

Video clip produced and narrated by Dr. M. Scott Echols.

Introduction

Fluid therapy is an important part of supportive care. Depending on the reptile species, maintenance fluids are estimated at 10 to 30 ml per kg per day. Replace deficits over 48 to 96 hours.

There are several routes available for fluid support. Subcutaneous and/or oral fluids are appropriate for mild to moderate dehydration. Administer intracoelomic, intravenous (IV), or intraosseous (IO) fluids to critically ill patients or for patients with moderate to severe dehydration. Regardless of the route selected, pre-warm fluids to the mid-range of the patient’s preferred optimum temperature zone. For many reptiles, this means the target temperature is approximately 80°F or 26.7°C. Both IV and IO catheters can be used for bolus or constant rate infusion for up to 72 hours.

 

Intraosseous catheters in reptiles

Intraosseous catheters are more commonly used than IV catheters in lizards. Although IO catheter placement requires sedation or general anesthesia and pre-emptive analgesia, IO catheters are also more secure and can be used in lizards that weigh as little as 50 grams. Intraosseous catheters are contraindicated with sepsis or metabolic bone disease.

 

Lizards

The preferred site for an IO catheter placement in the lizard is the tibial crest. Other potential sites include the proximal humerus, ulna, and distal femur.

To place an IO catheter in the lizard:

  1. Select a needle of appropriate size. A spinal needle is preferable to prevent a bony core from blocking the catheter. In small lizards, use a 23 to 27 gauge hypodermic needle. Needle length should be approximately one-third to one-half of bone length.
  2. Insert the needle on the medial aspect of the tibial plateau. Enter at the craniomedial aspect of the bone to prevent invasion of the joint capsule (Fig 1).

    Insert the needle on the tibial plateau. As always in reptiles, insert the needle between, not through, scales.

    Figure 1. Insert the needle on the tibial plateau. As always in reptiles, insert the needle between, not through, scales. Click image to enlarge.

  3. Direct the needle straight along the long axis of the bone using steady pressure.
  4. Once through the cortex, the needle should pass easily until the hub is against the skin.
  5. Palpate the entire length of the bone to ensure the needle tip did not inadvertently exit from the cortex.
  6. If the needle is seated properly, the limb can be moved using the needle hub.
  7. Confirm correct placement by aspirating bone marrow or flushing with a small volume of heparinized saline. Survey radiographs can also be used to confirm catheter placement (Fig 2). Obtain two views whenever possible.

    Survey radiographs can be used to confirm intraosseous catheter placement. <em>Click image to enlarge.

    Figure 2. Survey radiographs can be used to confirm intraosseous catheter placement. Click image to enlarge.

  8. Secure the needle with tape.
  9. A fluid or syringe pump will be necessary to push fluid through the IO catheter (Fig 3).

    A leopard gecko receiving intraosseous fluids via syringe pump.

    Figure 3. A leopard gecko (Eublepharis macularius) receiving intraosseous fluids via syringe pump. Click image to enlarge.

Snakes

There are no sites for IO catheter placement in snakes.

 

Chelonians

In many chelonians, the gular plastron is a good place to find cancellous bone, however jugular catheter placement is generally much easier than IO catheter placement in many turtles and tortoises.

 

Intravenous catheters in reptiles

As in other species, IV catheters require 24-hour monitoring because disconnection can lead to fatal hemorrhage.

Ventral abdominal, caudal veins

Catheterization of the ventral abdominal vein and caudal vein are used almost exclusively in anesthetized patients since maintenance of these sites is difficult in the conscious patient. There is also danger of fecal contamination when the ventrum is dragged on the ground.

 

Cephalic vein

The cephalic vein is the vessel of choice for IV catheter placement in the lizard. Carefully perform a transverse cut-down, expose the vessel with blunt dissection, then insert an over-the-needle catheter of appropriate size.

 

Jugular vein

The jugular vein can be catheterized in snakes, lizards and chelonians.

Squamates

A surgical cut-down is required in snakes and lizards. A small, full-thickness skin incision is made to directly visualize the jugular.

 

Chelonians

The jugular vein is the preferred site for IV catheter placement in most turtles and tortoises. Reserve jugular catheterization for chelonians that are chemically restrained or minimally responsive because otherwise these catheters are very difficult to maintain.

The chelonian jugular vein is located at the level of the tympanic scale on the dorsolateral surface of the neck (Fig 4 and Fig 5). Dorsal and ventral branches of the jugular vein run directly along the neck from the dorsal and ventral borders of the neck. The dorsal branch is closely associated with the carotid artery. If the artery is inadvertently entered, hematoma formation is likely. The right jugular vein is slightly larger than the left and is therefore the best choice for catheter placement.

The jugular vein is located at the level of the tympanic scale on the dorsolateral surface of the chelonian neck.

Figure 4. The jugular vein is located at the level of the tympanic scale on the dorsolateral surface of the chelonian neck. Click image to enlarge.

An anatomy overlay illustrates the tympanic scale (green) and jugular vein (blue).

Figure 5. An anatomy overlay illustrates the tympanic scale (green) and jugular vein (blue). Click image to enlarge.

To place an IV catheter in the chelonian jugular vein…

  1. Fully extend the neck.
  2. The superficial jugular vein can often be visualized through the skin (Fig 6), however apply digital pressure at the thoracic inlet to ‘pop up’ the vessel or perform a “cut down” as needed. Alternatively ultrasound can be used to find the jugular vein in large patients.

    The superficial jugular vein (arrow) can often be visualized through the skin.

    Figure 6. The superficial jugular vein (arrow) can often be visualized through the skin. Click image to enlarge.

  3. Perform a sterile preparation of the skin overlying the vessel.
  4. Insert an over-the-needle catheter of appropriate size either through a “cut-down” or percutaneously.
  5. Use a butterfly piece of tape to stabilize the catheter, then suture or glue the catheter to the skin.
  6. When the catheter will be maintained in the conscious patient, cover the setup with a light wrap.

Heart

Intracardiac catheter placement has also been described for emergency or short-term delivery of fluids to the moribund snake.

 

Patient monitoring

  • Weigh patients receiving fluids at least once or twice daily.
  • Monitor urine output.
  • Observe the reptile closely for evidence of overhydration such as serous nasal discharge and tachypnea.

Removing the catheter

Simply remove the catheter and place a light bandage consisting of elastic bandage material with gauze or cotton.

 

References