intravenous infusion filter, any of the numerous devices used to help ensure the purity of an IV solution. IV filters strain the solution to remove such contaminants as dissolved impurities (detergents, proteins, and polysaccharides), extraneous salts, microorganisms, particles, precipitates, and undissolved drug powders. Any such contaminants may complicate the IV therapy and patient recovery. Some filters are built into the primary IV tubing; others must be attached. One of the main criteria for selecting a filter is the assurance that the filter is not too fine for the IV solution to be strained; filters that are too fine clog. The size of filter membranes varies from 5 to 0.22 μm. Filters of 1 to 5 μm will remove most particulate debris but not most fungi or bacteria. Filters that are 0.45 μm or less remove fungi and most bacteria; filters that are 0.22 μm remove all fungi and bacteria but also reduce the flow rate of the IV solution, which is crucial when rapid delivery is required. See also needle filter.
