<qa>  What is the heparin lock enclosed in?7 AM - Blood pressure is measured, EKG and EEC leads are placed, a heparin lock is inserted, and a blood sample is drawn. The heparin lock is a thin needle enclosed in a thin plastic tube. The needle guides the tube into a vein and is then removed, leaving the tube in place. The indwelling tube allows multiple blood samples to be drawn without repeated needle sticks. 