The incidence of infection is related to the length of time the cannula remains in situ.
The catheter tip may be infected secondarily by organisms already infecting the hub or insertion site which track down the catheter lumen or tunnel, but it may also acquire organisms from fluids passing through it or from the bloodstream itself.

Most central venous line-associated infections are caused by organisms from the skin near the exit site which gains access to the intravascular segment of the cannula.

Sample collection:


Disinfect the skin around the cannula entry site, remove cannula using aseptic technique, and cut off 4cm of the tip into a Universal container using sterile scissors and send this to the laboratory.

Cannulae should only be sent if there is evidence of infection.


Cannula associated swabs (eg swabs of catheter insertion sites) may be employed as alternative specimens. However, routine investigation of cannula associated swabs from asymptomatic patients is of dubious value.