What Is a Blood Culture?
A blood culture is a sample of blood, drawn from the body, that is used to determine if there are any infections or other harmful elements present in the blood. Drawing blood is a procedure performed by a phlebotomist or nurse who uses modern methods to ensure the blood is taken safely and hygienically.
The act of drawing blood is called phlebotomy, and the most common way of drawing blood is through a process called venipuncture. Venipuncture involves the puncturing of a vein with a thin needle and extracting the blood through the needle. The phlebotomist locates a suitable vein, usually on the front of the forearm below the elbow, and applies a tourniquet above the location to create extra pressure. This pressure causes the vein to stand out, making it easier to puncture successfully.
The two most commonly used devices for venipuncture are:
• Vacuum Tube - The needle used with a vacuum tube contains a sharp rear, with a plastic protecting guard. The vacuum tube is pushed on to that sharp rear, puncturing the tube and allowing blood to rush in. The tube is self-sealing, when it is removed from the needle’s posterior. In this manner, several tubes can be filled from the same puncture, if needed, eliminating the need for multiple punctures.
• Syringe - When a slower, more controlled way of drawing blood is necessary, a syringe is used. The syringe is most commonly used in young children and the elderly, who may have sensitive or fragile veins that could potentially become damaged or even collapsed from the suction of a vacuum tube. With a syringe, the phlebotomist is able to slowly draw the needed amount of blood.
A finger stick involves pricking the forefinger and collecting the blood that comes out. The prick is performed with a lancet, a single-use device that shoots out a small metal needle into the front of the finger. The metal portion of the lancet will usually retreat back into the protective cover, after the prick is finished, to prevent any accidental puncturing. The lancet is then disposed of in the appoprriate container.
The blood is collected by applying slight pressure to the finger and guiding the blood that oozes out into a narrow tube that runs into the collection vial.
The phlebotomist or nurse should follow a few important procedures, in order to ensure safety during the blood drawing process.
• Proper Gloving and Clean Hands - Phlebotomists glove-up to keep themselves, and their patients, safe from any possible contaminents. They frequently wash their hands and wear a fresh pair of gloves for every patient, to avoid the possibility of cross contamination.
• Cleaning the Area - Phlebotomists clean the puncture site with a treated pad, to eliminate risk of any contaminents entering the sample. They then place a gauze against the spot of the puncture, when removing the needle, to ensure blood doesn’t leak out. A bandage or gauze and tape will usually be applied, to keep the area safe while it heals.
• Confirming Patient ID - This is done by confirming name, birthdate, and patient number with a patient’s armband. These identification markings must match perfectly with the requisition form, to ensure the correct blood draws are being performed on the correct person. Labels with the patient’s printed information are applied to vials, to ensure proper identification by the employees who work in the lab.
• Color Labelled Tubes - Different tubes have different chemicals in them that react to the blood in various ways. These tubes are color-coded, to ensure they are tested correctly.
• Proper Needle Disposal - Hospitals and doctor’s offices have “sharps containers” that safely hold used needles until they can be safely disposed of.
Blood Culture Information, https://www.webmd.com/a-to-z-guides/blood-culture
Venipuncture and Finger Stick Instructions, https://library.med.utah.edu/WebPath/TUTORIAL/PHLEB/PHLEB.html
Tube Colors, https://www.medicine.uiowa.edu/path_handbook/Appendix/new_tubes/tube_tops.html