Advanced catheterization (Proceedings)

Central line placement has become practical, affordable, and more often indicated in veterinary practice. Most private practices, referral practices, or larger settings have everyday indications for placement of these longer duration catheters. Central line placement simply means placing an indwelling catheter into a central vein, specifically either the cranial or caudal vena cava. Technicians should become familiar with the types of catheters available and typical placement sites and procedures.

Single lumen vs. multi-lumen

Various manufacturers make central lines and there are single lumen and multi-lumen catheters. Single lumen catheters have one lumen that resides in the vessel whereas multi-lumen catheters have separate, non-communicating lumens that run within the outer shell of the catheter. Keep in mind that the single or multi-lumen designation does not pertain to how many fluid line enter into the hub of the catheter. Some single lumen catheters may have several fluid ports, or pig tails, that connect at the hub or entrance of the catheter. But these catheters have only one lumen chamber where the fluids would intermingle. True multi-lumen catheters have one to three lumens that do not communicate in any way. The exit sites of the various lumens are at different locations at the distal end of the catheter shaft so as to protect the infusions from mixing before they are delivered into the vein. There are many advantages of utilizing a multi-lumen central line. These include simultaneous administration of incompatible solutions, continuous monitoring of central venous pressure while administering fluids, administration of irritant solutions (TPN) while administering fluids, and repeated atraumatic blood sampling.

Placement technique

Three types of placement techniques are common for central venous catheterization; with these being over the needle, through the needle, and over a guide wire (Seldinger) technique. Over the needle catheters vary greatly in size, length, and material. These catheters are commonly used as peripheral catheters and less commonly utilized as central lines. Generally these catheters are for short term usage, and a major disadvantage is they require large needles that increase in size as the catheters increase in size. Typically the over the needle catheters are made from rigid materials and may kink and cause discomfort to the patient and trauma to the vessel.

Through the needle catheters are more common than over the needle for central line placement. Several manufacturers and brand names exist, but all catheters are delivered into the vein through a needle. Some brands have split apart, winged needles that are removed entirely; while others have a needle guard that remains at the proximal end of the catheter and is incorporated into the bandage. The catheters that require a needle guard are often difficult to secure without kinking. Again the disadvantage exists of the required large size of the needle for the catheter to pass through. The final technique is an over the wire technique that will be discussed in detail.

Seldinger technique

This technique uses a small guage introducer to perform the venipuncture followed by a small atraumatic guide wire passed through the introducer into the vein. After the vein is entered, several smaller steps are then performed to pass the larger bore central venous catheter. There are several choices of introducers which is just a fancy name for the tool you choose to perform venipuncture.

A needle alone may be used to hit the vein; or a needle with a regular syringe attached may feel very familiar for technicians. A specialized Seldinger syringe may also be used to perform venipuncture. This syringe has a wire guide, or channel, through the entire length of the syringe from butt end of the barrel all the way up the syringe and exiting the point end of the needle. After establishing venous access with this syringe and needle, the wire is passed through the syringe and out the needle into the vessel. And finally another choice of introducer is a small sized, over the needle catheter, can easily be used as an introducer.

Many factors, primarily comfort and past experience, can play a role in what type of introducer a technician uses to first establish venous access. However, the single most important point is to ensure that the wire will pass through the introducer of your choice before you perform venipuncture. I would dare say that many a placement has been aborted after an introducer was seated in the vein only to find that the guide wire would not fit through the introducer. Perform a "test run", to ensure the guide wire will pass through, if an introducer is used other than what is provided in the manufacturers pack.

The big advantage of over the guide wire technique is the larger sized central catheter which was started with a smaller needle to make the venipuncture. Patient comfort and overall success rate seem to increase with this technique since the technician is working with a flexible guide wire within the vessel as opposed to a sharp needle that must be held steady within the vessel while the central catheter is placed. The step by step placement process will be discussed next.

Step by step placement process using over the guide wire (Seldinger) technique of multi-lumen catheterization in the jugular vein

1. Determine desired number of lumens for anticipated medical therapies

2. Determine appropriate length of catheter for patient. Measure from anticipated point of insertion (middle of jugular vein) to the second rib space. Distal end of catheter should terminate cranial to the right atrium.

3. Develop sedation protocol as appropriate for patient's medical status. Most every patient will benefit from slight sedation during this procedure and most cats require it.

4. Ready all supplies necessary for procedure including heparinized saline bag to use for flushing ports of catheter before placement.

5. Sedate patient and utilize pulse oximetry and or ECG in order to monitor patient.

6. Clip and prep right jugular vein. Using the jugular vein on the right side will save the left side of neck for any future need of esophagostomy feeding tube. Hair should be clipped from a large area to provide 2-3 inches of sterile field around the catheter placement site.

7. Open your catheter pack and sterile gloves. Open your desired introducer if using an instrument other than the pack equipment.

8. Put on sterile gloves.

9. Have an assistant hold the sterile hep saline bag and aseptically pull up several syringes of hep saline.

10. Flush all ports of multi-lumen catheter with hep saline and return catheter to pack.

11. Place drape on patient and have assistant hold off jugular vein under drape.

12. Palpate jugular vein and determine ideal location of venipuncture.

13. Instruct assistant to release jugular vein pressure. Make stab incision with #11 scalpel blade with cutting edge of scalpel facing up. Make a full thickness skin incision but do not slice and do not nick jugular vein.

14. Instruct assistant to reapply pressure at thoracic inlet and perform venipuncture with your chosen introducer.

15. Straighten J-end of guide wire and feed wire through introducer into vein until it meets resistance/stops or until it reaches your introducer device.

Regarding introducer choice and introducing the guide wire ---

A. If needle alone is used, it will be helpful to instruct the assistant to keep holding off the vein until the guide wire is fed down the needle and started into vein. Occasionally the vein will "slip" back off the needle if the jugular vein is released before the wire is in the vein.

B. If needle and regular syringe is used, aspirate a small amount of blood to confirm venipuncture and then remove the syringe and thread guide wire through needle. Jugular pressure may or may not need to continue depending on whether the needle is advanced into the vein only slightly.

C. If a specialized Seldinger syringe is utilized, aspirate a small amount of blood to confirm venipuncture and then thread the guide wire through the whole in the barrel end of the syringe. Feed guide wire all the way through needle into vein.

D. If an over the needle catheter is used, the catheter is advanced into the vein right after viewing an initial flash of blood within the stylet hub. The catheter is then seated completely into the vein and the stylet is removed. The guide wire is then passed through the catheter.

16. Once the guide wire is placed into the vein, the introducer is removed. Only the guide wire is remaining.

17. Next the vessel dilator is fed over the wire and advanced (do not advance until the guide wire has extended beyond proximal end of dilator). The wire must always be within reach so that it is not inadvertently lost within the vein. A pushing/twirling motion should be used and the dilator is advanced about ¾ of the length.

18. The dilator is removed and sterile gauze is applied for hemostasis as the vessel now has a larger defect. Once again only guide wire is left in the vein.

19. Now the multi-lumen catheter is fed over the wire and inserted. Remember the wire must extend beyond the port end of the catheter (and is therefore within reach for removal). Both wire and catheter can be advanced during insertion of the catheter.

20. Hold the catheter in place and pull the wire out of the catheter. Large bore multi-lumen catheter is now in place.

21. Secure the catheter with a suture through each wing of catheter hub. Do not over tighten these sutures. One more suture is placed at the suture guide and snugged into place.

22. A bandage is applied utilizing sterile 4x4's from the catheter pack.

23. Extension sets primed with hep saline are applied and anchor loops are taped to prevent direct pulling on the catheter.