Catheterized rodent models are particularly useful when studies involve repeated access to a laboratory animal over time. Rather than performing multiple needle sticks for injections or blood collection, surgically implanted catheters provide consistent access while minimizing stress and handling.
This article presents considerations for choosing a catheter method, understanding durability, and improving long-term catheter patency to enhance the efficiency and success of preclinical studies.
When to Use a Catheterized Surgery Model
For short-term or single-dose studies, a standard procedure may be sufficient. However, for longer studies involving frequent sampling or repeated procedures, surgically implanted systems become increasingly valuable for both data integrity and animal welfare.
In some cases, a lab animal may need multiple catheterizations or a combination of surgeries, which can be performed during a single surgical time point.
Catheter Exteriorization Options
Catheters can be externalized in several ways, including standard exteriorized lines and more advanced exteriorization systems, each with its own benefits and practical considerations.
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Standard exteriorization: The standard exteriorized catheter model features a fixed 2.5 cm exposed catheter length positioned between the shoulder blades and is secured. A removable stainless-steel plug allows easy catheter access, and configurations are available with either single or double catheters, depending on study needs.
The model offers several advantages, including a simple design, no requirement for specialized adaptors or injectors, and elimination of the stress associated with jackets or harness systems. It can also be readily adapted to alternative configurations, if needed.
However, animals cannot be group-housed, and some may reach the externalized catheter, increasing the risk of catheter damage, removal, or vessel dislodgement. Sutures and wound clips may need to be replaced over time, and catheters must be clamped during access procedures. -
PinPort™*: This catheter system uses a self-sealing access port in place of a standard sterile catheter plug, creating a closed system that is easier to access and helps reduce contamination risk. However, the system requires specialized adaptors or injectors and comes with additional port-related costs.
Similar to a standard fixed catheter, animals cannot be group housed, and some may still be able to reach the catheter, increasing the risk of catheter damage, removal, or vessel dislodgement. Sutures and wound clips may require periodic replacement, though unlike standard exteriorized catheters, clamping during access is not required. -
Harnesses: A harness-based catheter system is available in single, double, triple, and quad configurations and utilizes self-sealing ports for access. The design eliminates the need for suture or wound clip replacement and supports convenient tethering for infusion studies or automated blood sampling. Specialized caps are also available for bile duct-cannulated closed-loop (BDCCL) models to enable closed bile recirculation.
Researchers should consider the added cost of harness systems, the need for compatible adaptors or injectors, and the inability to group house animals. Harnesses also require regular adjustment as animals grow and may cause temporary stress during acclimation. -
Buttons: With single, double, triple, and quad configurations, buttons feature self-sealing ports for access. With no exposed catheters, the design improves protection, reduces contamination risk, minimizes blood flashback, and supports better long-term patency. Protective caps can also allow for group housing in certain applications.
Additional benefits include eliminating suture or wound clip replacement, easy tethering for infusion or automated blood sampling, and specialized caps for BDCCL models that require closed bile recirculation.
Compared to standard exteriorization methods, button systems involve higher costs, specialized access adaptors, and a more invasive surgical procedure with longer recovery times. Animals must also be large enough to support implantation.
Because buttons function as implanted foreign bodies within a subcutaneous pocket, some animals may develop swelling or seroma formation during healing. While most seromas resolve without affecting study use, a small number of animals may ultimately reject the implant.
The Importance of Maintenance and Patency
Catheterized models require active maintenance throughout the study’s duration. This includes routine flushing, patency checks, and, in some cases, replacement of external components such as sutures or wound clips.
Catheter patency refers to the ability to flush an intravascular catheter with saline and withdraw blood without restriction, whereas partial patency describes situations in which infusion is possible, but blood withdrawal is impaired.
Maintaining patency depends on proper surgical technique, component selection, adequate recovery time, careful post-surgical care, and routine catheter maintenance. Best practices include aseptic technique, maintaining a closed system, applying positive pressure during syringe removal, and using locking solutions to prevent clot formation and microbial contamination.
Patency issues may result from physical or biological changes over time. Animal growth or catheter movement may alter the original catheter position, causing the catheter tip to rest against the vessel wall, kink, or become partially displaced from the vessel. Inflammation within the vessel or seroma formation at button implant sites may also contribute to reduced catheter performance. If clot formation occurs, partial patency loss can progress to complete catheter failure, making proper flushing and maintenance techniques essential for long-term study success.
Enrichment Considerations for Surgically Modified Rodent Models
As with other animal models, enrichment is equally important in surgical models. Multiple forms of enrichment should be included, such as gnawing materials, chew blocks, and supplemental bedding enrichment, beginning immediately after surgery and continuing during and after delivery to the researcher’s site.
Once at the site, researchers should be aware that certain housing features, such as tunnels, huts, or low-hanging feeders, can place unnecessary pressure on buttons or harnesses.
Catheterized Surgical Models: A Valuable Tool for Research
Surgically catheterized rodent models provide researchers with valuable tools for generating high-quality, repeatable data while reducing procedural stress on animals. But their success depends on more than just surgical placement. Thoughtful catheter selection, proper maintenance procedures, and appropriate enrichment all play critical roles in promoting reliable outcomes and animal welfare.
Learn more about how we can support your research with our mouse and rat catheterizations and exteriorization options.
*PinPort™ is a trademark of Instech Laboratories, Inc., Plymouth Meeting, Pennsylvania, USA.
