The biological, chemical and physical properties which are required for optimal vascular catheter design and construction are listed in detail in Table 1. There are many considerations, for example:
- Vascular catheters come in contact with blood and vascular endothelium, as well as other body tissues such as skin and connective tissue. The intravascular implants can rapidly become coated in biofilm derived from the animal's circulating blood. The biofilm acts as a substrate for thrombosis and microbial colonisation. The nature of the catheter material and any surface coatings applied influences the quality and quantity of biofilm that forms.
- Catheters should be compatible with the chemical compounds or solvents administered during experiments and must not bind substances of interest during blood withdrawal.
- Catheter strength and durability are also important properties.
Table 1. Desirable properties of vascular catheter materials.
Given the many biological, chemical and physical properties which are required for optimal vascular catheter design it is perhaps not surprising that only a few naturally occurring and synthetic materials have proved suitable for constructing vascular catheters. In practice, there is no single material that can be used for all applications and therefore catheter materials need to be selected based on an assessment of the intended application. For example:
- Flexible catheters can reduce endothelial injury which can lead to thrombosis, but they are more difficult to insert. The training and experience of the surgeon are vital factors in optimising catheter implantation and ensuring successful outcomes.
- Surface coatings modify catheter properties such as thrombogenicity, friction coefficient or antimicrobial properties, but in experimental surgery it must be remembered that coatings applied to implants may be biologically active and capable of influencing data. Pilot studies may be required to generate data characterising changes caused by such materials and consideration should be given to suitable controls in experiments.
- The physical shape of a catheter tip can play a significant role in reducing endothelial trauma. Many commercially available catheters have a rounded tip (Figure 1) which is considered to be less traumatic than square cut tubing or bevel ended tubing, although the latter is easiest to insert.
Figure 1. Detail of a rounded tip of an intravascular catheter: this design helps to minimise trauma to the vascular endothelium
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