Catheter design

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. 

Biological

  • Non-irritant - provokes minimal inflammatory response
  • Non-carcinogenic - low tendency to cause neoplasia
  • Non-thrombogenic - low tendency to cause blood clotting
  • Non-toxic
  • Resists microbial adhesion
  • Resists biofilm deposition

Physical

  • High tensile strength
  • Resists compression - maintains lumen patency
  • Optimum flexibility
  • Low friction coefficient
  • Dimensional stability
  • Tolerates physical sterilisation methods (e.g. heat, steam, irradiation)
  • Ease of fabrication (e.g. heat forming or welding)
  • Non-permeable (water, gases, solvents)
  • Radiopacity - ability to image catheter with X-rays

Chemical

  • Absence of leachable additives (e.g. catalysts and plasticisers)
  • Stable during storage
  • Stable on chemical sterilisation
  • Stable on implantation (non-biodegradable)
  • Permits adhesives in fabrication (possibility of bonding dissimilar materials)
  • Accepts surface coatings (e.g. hydrogel, antithrombotic, antibacterial)
  • Compatibility with chemical compounds and solvents (absence of absorption and chemical reaction)
  • MRI (Magnetic Resonance Imaging) compatible


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

Resources and references

  • Swindle MM et al. (2005) Vascular access port (VAP) usage in large animal species. Contemporary Topics in Laboratory Animal Science 44(3): 1-17.
  • Colas A & Curtis J (2004) Silicone biomaterials - history and chemistry. In Biomaterials Science: An Introduction to Materials in Medicine. Eds: Rutner BD, Hoffman AS, Schoen FJ, Lemons JE (eds.). pp. 80-86. Elsevier Academic Press: Boston.
  • Colas A & Curtis J (2004) Medical applications of silicones. Biomaterials Science: An Introduction to Materials in Medicine. Rutner BD, Hoffman AS, Schoen FJ, Lemons JE (eds.), pp. 697-707. Elsevier Academic Press: Boston.
  • Brown JM (1995) Polyurethane and silicone: myths and misconceptions. Journal of Intravenous Nursing 18(3): 120-122.
  • Passerini L et al. (1992) Biofilms on indwelling vascular catheters. Critical Care Medicine 20(5): 665-673.
  • Gott VL et al. (1964) Technique of applying graphite-benzalkonium-heparin coating to various plastics and metals. Transactions of the American Society for Artificial Internal Organs 10: 213-217.
  • Grode GA et al. (1969) Nonthrombogenic materials via a simple coating process. Transactions of the American Society for Artificial Internal Organs 15: 1-6.
  • Keogh JR & JW Eaton (1994) Albumin binding surfaces for biomaterials. Journal of Laboratory and Clinical Medicine 121: 537-545.
  • Tebbs SE & Elliott TSJ (1994) Modification of central venous catheter polymers to prevent in vitro microbial colonisation. European Journal of Clinical Microbiology and Infectious Diseases 13(2): 111-117.
  • John SF et al. (1995) Adhesion of staphylococci to polyurethane and hydrogel-coated polyurethane catheters assayed by an improved radiolabelling technique. Journal of Medical Microbiology 43: 133-140.
  • Marconi W et al. (1995) New polyurethane compostions able to bind high amounts of both albumin and heaprin - Part 1. Biomaterials 16: 448-456.
  • Guiding principles for preparing for and undertaking aseptic surgery: A report by the LASA Education, Training and Ethics section.
  • Methods in vascular infusion biotechnology in research with rodents.
  • Refining procedures for the administration of substances.
  • Removal of blood from laboratory animals and birds.

Other resources on vascular catheterisation

 Click here for information on preventing thrombosis when implanting catheters in laboratory animalsClick here for information on preventing infection when implanting catheters in laboratory animalsClick here for information on planning and designing experiments which will involve implanting catheters into laboratory animalsClick here for a glossary of terms used in our pages on implaning catheters into laboratory animals