The collection area is most commonly cleansed with a 70% alcohol-based solution, which serves to reduce the risk of introducing skin contaminants into the bloodstream and into the blood sample being collected. For certain laboratory tests, including blood cultures, the use of an iodine-based solution is used to further prevent microorganisms from contaminating the blood sample.
While draw preparation solutions are generally considered inert and will not affect the measurands, occasionally precautions must be taken to avoid the use of isopropanol or ethanol-based prep pads if the patient is being tested for toxic alcohols or for legal blood alcohol testing. In these situations, the cleansing agent used must not contain alcohol or other volatile organic substances. Use a non-alcohol antiseptic should be used, such as povidone iodine. Tincture of iodine should not be used because it contains alcohol. Similarly, if the patient is being tested for halides, such as iodine, the site should not be prepared with an iodine-containing solution.
After cleansing a collection site with an alcohol-based solution, allow the area to air dry, as residual alcohols on the skin may be introduced into collection tubes, and may increase the risk of cellular hemolysis.