A Pragmatic Approach to Prevent Premature Failure of Ultrasonically Guided Catheter (Cannula)

Infiltration occurs when infused drugs and fluids accumulate in surrounding tissue. The size and depth of the veins relative to the size of the cannula, in-situ thrombi, length of the catheter inside the lumen of the vein and the use of hyperosmolar solutions are implicated. Smaller the size of the vein, higher the risk of infiltration. It is recommended to choose veins with an antero-posterior diameter of at least 4 mm in some studies, although much smaller veins could be cannulated with appropriately sized catheter. The ratio between the external diameter of cannula to antero-posterior diameter of vein comes to play in minimizing infiltration, as essentially a ratio of < 0.3 or catheter occupying less than one-third of the area of the venous lumen is associated with reduced incidence of infiltration. Similarly, increased length of the catheter inside the lumen, lessen the risk of infiltration. Ultra-long or midline catheters and use of superficial veins have been proposed in view of increasing the in-situ length. The plane of ultrasonic view, either long-axis or short-axis, was not found to be superior to one another in averting infiltration. The figure 1 illustrates an ultrasonically placed peripheral cannula without PCF.