Thus the femoral vein, once located, allows for femoral venipuncture.. Some health care workers prefer to use a syringe-needle technique for venipuncture. This protection is important during venipuncture (taking blood) from the median cubital vein. These individuals are at risk for accidental injury to the ulnar artery during venipuncture. In venipuncture, Vacutainer brand blood collecting tubes containing heparin usually have a green cap. Bruising can also occur during or after venipuncture. Repeated platelet donations at short intervals will cause the venipuncture site to scar. Blood samples can be obtained through venipuncture of the mother. Children's memory and suggestibility were assessed for a medical examination and venipuncture. It is most commonly used during dental work, venipuncture, and other medical procedures. The butterfly's precise placement facilitates venipuncture of thin, "rolling", fragile, or otherwise poorly accessible veins. Non-pharmacological treatments for pain associated with venipuncture in children includes hypnosis and distraction. However, in the case of hemochromatosis, bloodletting (by venipuncture) has become the mainstay treatment option. The procedure itself is known as a venipuncture. Despite the potential risk, the evidence for such complications subsequent to venipuncture is limited.