The use of indwelling cannulae/catheters for reliable intravascular access is an essential feature of modern health care for both monitoring and intervention. Insertion of intravascular cannulae and catheters allows continuous and painless access to the circulation for administration of fluids and electrolytes, medications, blood products and nutritional support. In addition the intravascular access can be used for blood sampling, haemodynamic monitoring, haemodialysis and haemofiltration.
Specific examples of descriptions of cannulae, defining their siting, use or design, include:
- Peripheral e.g. Venflons, Abbocaths.
- Central lines e.g. triple lumen, subclavian lines, jugular lines, femoral lines.
- Monitoring lines e.g. central venous pressure lines, Swan Ganz lines, arterial lines.
- Long term access e.g. Hickman lines, Broviac lines, Portacath.
- Miscellaneous e.g. Vascath for haemofiltration, and umbilical cannulae for exchange transfusions in neonates.
- Antimicrobial coated or impregnated CVCs: recent studies have demonstrated that antimicrobial coated or impregnated CVC can reduce the incidence of catheter colonisation and CR-BSI in appropriate situations.
Cannula tip culture gives valuable information but necessitates the removal of the cannula. This can sometimes result in the loss of venous access that can interfere seriously with the medical management of the patient, although sometimes catheter removal is necessary to gain control of a catheter-related infection, especially with certain organisms, such as Candida species.
Cannula associated swabs (e.g. 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.
Culture of the skin around insertion sites or of cannula connectors (hubs) is becoming increasingly used in confirming cannula site infection. This is reported as having high sensitivity and specificity but is only useful where there is clinical evidence of localised infection, as positive culture results may reflect the presence of commensals and be misleading. Careful interpretation of these culture results should be correlated with blood culture isolates.
