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.
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.