80% of all patients admitted to hospital have an intravenous cannula inserted as part of their treatment. Despite substantial progress with the inception of care
bundles to reduce infection rates, peripheral cannulation still carries great infection risks, including introducing MRSA into the patient. Organisms causing cannula related noscomial infections can originate from the patients skin flora and a lack of aseptic insertion technique by the administering healthcare professional. The effects of such an infection range from “discomfort to the patient, prolonged or permanent disability and patient death.”1
More than 50% of all outbreaks of hospital acquired bacterae
mia or candidaemia reported in the world literature between 1965 and 1990 originated from vascular devices2,3 and between 5% and 25% of intravascular devices are found to be colonised by skin organisms4. The ideal catheter, a catheter that combines low-co
st coating technology, wide-spectrum and long-lasting antimicrobial properties, and safe utilization, has yet to be developed. The Department of Health has set targets for the NHS to reduce MRSA infection rates by 29% during 2012-2013.
Nationally, hospital trusts have developed their own local guidance on how to reduce complications associated with inserting an intravenous cannula. Universally, the guidance encourages improvements in technique, preparation, adequate monitoring and documentation. However, there is no focus on improving the device itself being inserted.
Coating intravenous cannulae with non-toxic particles of silver nitrate will reduce infection rates associated with device insertion. The released silver is active against microorganisms commonly found responsible for noscomial infections. It accumulates at the site of insertion thereby enhancing local protection against infection with no risk of systemic toxicity. The anti-microbial properties of silver have long been known about whereby silver disrupts the energy metabolism and electrolyte transport systems, when it binds to bacterial proteins.
Research in animals has already demonstrated the safety and efficacy of using silver nitrate to tackle the commonly offending micro-organisms. The increased costs of the cannula are outweighed by the savings made due to reduced use of antibiotics, reduced hospital stay due to patient complications and decreased morbidity and mortality experienced by patients5.
A- Staphylococcus aureus without silver treatment as found on a catheter
B- Staphylococcus aureus on a silver-containing material with microdispersed silver particles throughout the matrix.
We therefore propose the coating of intravenous cannulas with silver nitrate nanoparticles.
To develop this intravenous cannula, we have decided to use the same cannula currently in use in clinical practice to aid familiarity and reduce manufacturing costs. With regards to the coating, we have sourced the materials necessary to coat the cannula from the current evidence base. The most effective method of coating catheters appears to be melting silver in a microwave oven and pouring over plastic intravenous catheters placed in screw cap tubes. The tubes are then centrifuged to remove the air trapped inside the catheters and quickly placed in a thermostated oven set at 53°C. After 16 h, the coating solution is removed and the catheters are rinsed with various aqueous solutions. After which, the catheters are placed on bench-top paper, dried and sterilized (autoclave at 121°C for 15 min), ready for use.
WHO STANDS TO BENEFIT
Patients throughout all medical and surgical disciplines would benefit from this innovative and simple solution. Reducing peripheral cannulation infection rates would reduce ensuing local and systemic consequences of cannula associated infection. Reduced patient morbidity and mortality will parallel reduced healthcare costs. For example, abolish the 3-10days added to a patients length of hospital stay, saving healthcare trusts an additional £4,000-£10,000 that is required to treat a patient with an infection than one without an infection6. Fewer infections will spare the use of antibiotics, which is in line with current public health measures trying to tackle antibiotic resistance. In addition, this innovative work has far reaching applications in addition to intravenous cannulas, reducing potential infection from all indwelling equipment used in medicine, such as central lines, pacemakes, urinary catheters and so on safely guarding all those admitted into hospital and in particular those that are most vulnerable, the immunocompromised patient.
THE NEXT STEPS…
The next steps involve obtaining the necessary materials and preparation of purifying solutions, and the application of silver nitrate onto the intravenous cannula. Parallel to developing the product, we need to work closely with the ethical committee to enrol the product into a prospective clinical trial to confirm safety and efficacy.
Our team comprises 2 junior doctors, 2 final year medical students and one design and technology recent graduate. By involving members who have clinical exposure, we were able to come up with the idea and the solution to this rife problem. Our technology team member was able to estimate costs of the design and the feasibility of the project. As our team included members of a medical and design and technology background, we were able to pool our ideas together and challenge each other’s ideas to ensure they worked and that any stumbling blocks had been considered and tackled.
1. National audit office.
2. Maki DG. Nosocomial bacteremia. Am J Med 1981;70:719-32.
3. Maki DG, Mermel LA. Infections due to infusion therapy. In: Bennett JV, Brachman PS, editors.
Hospital Infections. 4th ed. Philadelphia: Lippincott-Raven Publishers; 1998. p. 689-724.
4. Pratt RJ, Pellowe C, Loveday HP, Robinson N, Smith GW, Barrett S, et al. The epic project:
developing national evidence-based guidelines for preventing healthcare associated infections.
Phase I: Guidelines for preventing hospital-acquired infections. Department of Health (England). J
Hosp Infect 2001;47 Suppl:S3-82.
5. Antimicrobial surface functionalization of plastic catheters by silver nanoparticles. Roe D, Karandikar B, Bonn-Savage N, Gibbins B, Roullet JB. J Antimicrob Chemother. 2008 Apr;61(4):869-76.
6. Department of Health 2008.