Extravasation Risk Factors - The Technique

The elimination of human error can be considered to be impossible. In excess of 100,000 doses of chemotherapy and over 1,000,000 IVs are in progress each day, inevitably leading to some degree of human error. However, risk associated with these factors should be minimised by the use of good training and educational policy, not only as stand-alone courses, but, importantly on a continuing educational basis.

One of the greatest skills that individuals can bring to the administration of chemotherapy is the fact that it is routine for them. It is neither appropriate nor is it safe practice to administer chemotherapy on a 'when required' basis. It is a blind process where no two administrations will be similar, it is thus as much an art as a science.

More rigorous scientific thought can govern the selection of cannula; it inherently makes sense and has been demonstrated in a number of studies and through the National Extravasation Register, that rigid steel cannulas lead to more problems than flexible Teflon or Silicone cannulas. The selection of device or cannula is also influenced by the competing issues of biology and physics.

Flexible cannulas are supplied in a variety of widths and lengths and the biology of veins means that the smaller and shorter the cannula the less the trauma associated with the cannulation process. However, the physics of short narrow pipes means that smaller diameter pipes increase the resistance and decrease the flow of the fluid through them. Or conversely, the pressure of delivery has to be increased. The insertion of a cannula necessitates the puncture of the vein wall. This wall is relatively fragile. If the pressure of the blood is greater than that of the fluid entering the vein via the cannula,there is a risk of back-flow into the cannula, or of rupture of the vein around the cannula edge, leading to leakage. Vein walls contain small holes and therefore the greater the pressure of the incoming fluid, the greater is the chance of wall rupture.

There needs to be a series of professional judgements. For example, if the quantity of the necessary chemotherapy to be administered is a 2 mg / 2ml dose of vincristine, then probably a small paediatric cannula is appropriate. The science and technology of cannula have developed rapidly and there are now a number of high-tech developments, e.g. the Silicon/Teflon IV cannula, and the cannula materials that soften once exposed to the warmer internal body temperature of 37°.