Biomedical Engineering Reference
In-Depth Information
associated with a dei nite non-zero risk of bacterial and fungal infections.
Device-associated infections are the result of bacterial adhesion and sub-
sequent bioi lm formation at the implantation site. Sources for infectious
bacteria include the ambient atmosphere of the operating room, surgical
equipment, resident bacteria already in the medical device, etc. [101].
In addition to human pain and suf ering, direct medical costs associated
with such infections are extremely high and ot en result in the removal of
the medical device and therefore a new surgery. More than 2 million cases
annually of hospital-acquired infections are reported in the USA —over
half associated with medical implants. Medical devices such as end tracheal
tubes, vascular and urinary catheters, and hip prosthetics are responsible
for over one-half of nosocomial infections in the USA [102, 103]. In the
case of joint replacements, over 800,000 surgeries (around US$4 billion)
are performed annually in North America and this number is increasing
[104]. h us, there is an urgent need for signii cant innovation in the i eld
of bacterial infections associated with medical devices. h is innovation is
especially needed with regard to polymers most commonly used to build
medical devices [105].
h e main goal of treating the various types of wound infections should
be to reduce the bacterial load in the wound to a level at which healing
processes can take place. By maintaining a high local antibiotic concentra-
tion for an extended duration of release without exceeding systemic toxic-
ity [106, 107], local delivery of antibiotics by topical administration, or by
a local delivery device, addresses the major disadvantage of the systemic
approach. Antibiotics already incorporated in controlled-release devices
include amoxicillin, vancomycin, carbenicillin, tobramycin, cefamandol,
and gentamicin [108]. h e ef ectiveness of such devices is strongly depen-
dent on the rate and manner in which the drug is released [109]. h ese
are mainly determined by the material into which the antibiotic is loaded
and the type of drug. If the drug is released quickly, the entire drug could
be released before the infection is arrested. If release is delayed, infection
may set in further, thus making it dii cult to manage the wound. Also, the
release of antibiotics at levels below the minimum inhibitory concentra-
tion (MIC) may evoke bacterial resistance and this situation could inten-
sify infectious complications [110, 111].
2.7.1
Antibiotic-loaded Medical Devices
h e development of antimicrobial polymers is focused predominantly at
the prevention of microbial colonization rather than microbial adherence.
Antibiotic-loaded medical devices present a straightforward approach
