This protocol describes a reliable and reproducible technique for the insertion and maintenance of a tunneled Hickman catheter for long-term vascular access in a large animal model. The approach allows for convenient daily sampling of whole blood from awake animals and intravenous administration of medication and fluids. Some of the main challenges to the long-term central venous lines in large animals are infection and damages, as large animals are occasionally able to gain access to the lines and cause mechanical trauma.
To mitigate these challenges, our group has invented our special pouches that protects the line while still allowing easy access to the catheter. Central venous catheters are invaluable devices in large animal research as they facilitate a wide range of medical applications, but there is no consensus on the best practices for their insertion and maintenance. In response, we have proposed a protocol that comprehensively describes an approach for proper placement of a tunneled Hickman catheter in pigs that minimizes catheter related complications and morbidity.
The use of our approach in over 100 pigs has resulted in long-term patency and minimal complication rates. This protocol offers a method to optimize the lifespan of the Hickman catheter and guidance for approaching issues during its use. To begin, place the anesthetized swine on the operating table.
In the ventral field, make a four-centimeter incision between the trachea and the medial border of the sternocleidomastoid muscle. Divide the platysma and dissect the connective tissue to expose the internal jugular vein or IJV on the lateral border of the sternocleidomastoid muscle. Then, isolate three to four centimeters of the IJV by dividing its branches with 4-0 coated and braided non-absorbable suture ties.
Circumferentially dissect away from the surrounding connective tissue. At the cranial end of the IJV, pass a coated and braided non-absorbable suture tie twice underneath the vessel to create a loop around it. At the caudal end, pass a suture tie once underneath the vessel to create a sling.
For catheter exit site preparation, reposition the swine via lateral tilt toward the non-surgical side to expose the ipsilateral dorsal surgical field. Once the limbs are re-secured, with a number 10 blade scalpel, make a 0.5-centimeter puncture in the skin at the desired catheter exit site three centimeters lateral to the vertebral column and five centimeter caudal to the head. For tunneling of the catheter, remove the wet gauze and re-identify the isolated IJV segment.
Then, choose a target entry site for catheter introduction subcutaneously at the same depth as the IJV deeper than the sternocleidomastoid and between the two coated and braided non-absorbable suture ties. Hold the Hickman catheter introducer in the dominant hand in the dorsal surgical field, and suspend the remaining length of the catheter in the air above the sterile field. The non-dominant hand should be in the ventral surgical field.
Insert the introducer into the exit puncture site with the dominant hand pointing the tip of the device toward the non-dominant hand in the ventral field. Push the tip of the introducer superficially and medially to tunnel the catheter through the adipose tissue, feeling for the emergence of the tip with the non-dominant hand. Once the tip emerges at the target entry site, pull the introducer and catheter through the subcutaneous tunnel until the cuff of the main line is just underneath the surface of the skin of the dorsal field.
Cut the end of the catheter to approximately the length at which it would reach down to 1/3 of the length of the swine's sternum. Using Addison Brown forceps, grasp the middle of the isolated IJV segment and make a cut halfway through the vessel with curved Metzenbaum scissors. While holding the IJV segment, insert the vein pick into the caudal segment of the vessel.
While maintaining tension on the cranial suture tie, insert and thread the end of the catheter into the vessel caudally. Once the catheter is fully inserted, not the caudal suture tie once to temporarily secure the Hickman catheter. Once patency is confirmed, knot the caudal suture tie twice to secure the distal IJV segment around the intravenous catheter.
Then, knot the cranial suture tie once to occlude blood flow in the IJV segment. Once done, to close the ventral surgical site, first suture platysma simple interrupted sutures with a 3-0 braided absorbable suture. Then, close subcuticular running sutures with a 3-0 monofilament absorbable suture.
To secure the Hickman catheter to the animal's skin, orient the Hickman catheter so that it forms a U-shape. Then identify three points. The first point is within two centimeters of the exit site.
The second point is over the forked portion of the catheter where the red and white lines diverge. And the third point is at the top of the U between the first two points. At each point, place a three-centimeter piece of one-inch medical tape over the catheter to create a wing on each side.
With a 0 synthetic monofilament, non-absorbable polypropylene suture, secure each wing to the skin via a single simple interrupted suture. At the second point over the forked portion, add a single interrupted suture through the gap between the two lines and ensure that the knot lies on top of the tape to prevent irritation. Test the patency of the white and red lines outside the sterile field via blood draws and flushes using 10 milliliters of 0.9%normal saline and 10 milliliters of heparinized saline.
Once the catheter pouch with a desired number of flaps is created, align the hole and flap one with the point where the lines exit the collar, orienting it so that its opening is caudal. Ensure the pouch is on the midline or slightly lateral to the dorsal neck. Then pull the red and white lines through the hole in flap one, ensuring the lines lay flat between flaps one and two with flap three facing up.
Using a 0 synthetic monofilament, non-absorbable polypropylene suture, secure the pouch to the collar with a simple interrupted suture at each corner and midway along each end. Do not suture through the skin. In a representative cohort of 32 swine with endpoint ranging from eight to 132 days, 78.13 of Hickman catheters remained patent until the experimental endpoint.
Small repairs were required in 9.38%of cases, while rates of removal or replacement before and after 30 days were 9.38%and 12.5%respectively. Reasons for line compromises included displacement, puncture and internal blockage. However, timely repair and replacement demonstrated a 100%functional success rate without significant interference with data collection.
