Share this“Optimizing a polyurethane catheter for the jugular vein was integral in allowing for a patent, long-term infusion into our laboratory animals.” -Comment from an academic user
Selecting a vascular catheter in rodents that is appropriate for a particular study can be a daunting or complicated task even though at first this may seem simple, e.g. “I’ve used PE50 for years and it works great.” Choosing the right catheter can be simplified by using three words to describe catheter characteristics: reliability, resistance, and ROI. These “Three Rs of Catheters” are critical considerations in catheter selection to ensure a successful outcome.
Reliability
We define the reliability of a catheter as the length of time it remains patent for infusion or sampling. The catheter’s performance depends on factors including the catheter material characteristics (stiffness, tear strength, elastic memory) and its size (which is directly related to the vessel to be cannulated). It is essential to have catheterized animals that are functional for the duration of the study to help satisfy every researcher’s goal in reducing the number of animals used. Finding a reliable catheter begins with one simple question: “Which vessel will be cannulated?” Each vessel has unique demands and may require specific catheter sizes, modification, and material to ensure the desired patency.
Choosing a catheter that suits the vessel in size, stiffness, and ease of insertion will improve surgical and post-operative performance, ultimately increasing patency. The “standard” pre-clinical catheter material—polyethylene (PE)—has been used for many years because is easy to implant and relatively inert. The tip of a PE catheter is stiff, however, and may have sharp edges, which can cause vessel damage and reduced patency, making it less reliable than other materials for long term implantation. Fortunately, there are many choices of catheter materials available today to suit any vessel: silicone, Tygon (PVC), nylon, Teflon, polyurethane (PU), and, the more recent, polyethylene-lined polyurethane. Catheter materials that are more pliable than PE, such as polyurethane, have the advantage of softening at body temperature, which may enhance reliability by reducing vessel trauma during insertion and use.
To facilitate the selection of an appropriate catheter based on its intended purpose, Table 11,3was developed to highlight the reliability of various catheter types relative to the vessel, material, and catheter specifications. For example, in a long term sampling study using the femoral artery in rats,4 a durable polyurethane catheter with a small diameter (0.024”) would be optimal; where as the requirements of a catheter for an acute infusion in the jugular vein may best be served by a more flexible silicone catheter with a larger diameter (0.037”).
Figure 1: Cost Compairson of Catheter Materials and Modifications. The ROI of the catheter can be broken down into a few criteria: the material cost and the complexity of the catheter design.
Table 2 : Be advised, there are many different formulations of catheter materials. Test each new catheter with your chosen vehicle for best results. References: Chemical Compatibility of ALZET® Catheters, Nuijen B, Bouma M, et. al , Department of Pharmacy and Pharmacology, 19: 273–281, 2001. For chronic delivery it the responsibly of the researcher to determine compatibility.