It’s The Plumber. I’ve Come To Fix The Dog Infusion Catheter.
Posted on Jan 08, 2012 by SolomonScientific
Long-term fluid delivery through a dog infusion catheter is comparable to plumbing. There are pipes, connectors, valves, flowing fluid, and a central pump. And those pesky clogs. Catheter clogging (or rather, clotting) is the most daunting challenge facing researchers undertaking preclinical canine drug studies. These occlusions can be total (inability to push and aspirate fluids) or partial (usually the inability to aspirate blood).
The plumber has a few options to clear the pipes when a line implanted in the vein of a dog becomes occluded. These options comprise repositioning the animal, use of fibrinolytics, and waiting for another time or day.
Repositioning of the subject is an old trick which has no risk and occasionally yields success. Fibrinolytic use presents low risks (anaphylaxis has been described especially with streptokinase; less so urokinase and tissue plasminogen activator—“tPA”) and can be quite costly. But it has a reasonable probability of success (see the “stopcock method” for instilling fibrinolytics on page 932 of “Restoring Patency to Central Venous Access Devices”). Anecdotally it is quite common to hear of catheters which are not patent one day and which flow freely a day or more later.
The plumber also has preventive tools in his bag to reduce the risk of animal catheter occlusion. These tools include choosing an optimal lock and flush solution, flush tricks, catheter material choices, and surgical decisions. Multiple flush solutions are described in the scientific literature including saline with heparin, glycerol/heparin, heparin/antibiotic, fibrinolytics, and others. When these solutions are pushed in a pulsing manner, it may be possible to create turbulence resulting in a more robust removal of clotting materials from the catheter. The premium catheter materials to optimize thromboresistance are polyurethane, polyurethane with heparin coating (see CBAS® coating) and silicone. Over the past decade, use of silicone for chronic indwelling CVCs has diminished substantially. Softer materials typically are less thrombogenic than stiffer ones. And animal catheters with rounded distal ends are less traumatic to the intimal lining of blood vessels and thus less prone to potentiate clotting.
An additional imperative for reducing clots in these lab animal devices is the well-documented correlation between thrombi and infection in chronic central lines.
