A needle holder, sometimes called a barrel, is designed to:

A needle holder, often referred to as a barrel, is primarily designed to support a vacuum tube during blood specimen collection. This device securely holds the tube in place while also allowing for the safe and effective collection of blood samples. It ensures that the tube is stable during the procedure, which is crucial to prevent any contamination or improper collection of the specimen. By keeping the vacuum tube securely in position, the needle holder aids in maintaining the integrity of the blood sample until it can be processed in a laboratory setting.

While the other options may pertain to different aspects of medical procedures, they do not accurately capture the specific function of a needle holder. For instance, holding the patient still is more related to overall patient management during a procedure, administering medications typically involves syringes or other delivery systems, and stabilizing the needle during an injection is usually done through other means or tools specifically designed for that purpose. Thus, the designated function of the needle holder directly aligns with supporting the vacuum tube during blood specimen collection.