An arterial line (also art-line or a-line) is a thin catheter inserted into an artery. It is most commonly used in intensive care medicine and anesthesia to monitor blood pressure directly and in real-time (rather than by intermittent and indirect measurement) and to obtain samples for arterial blood gas analysis. Arterial lines are generally not used to administer medication, since many injectable drugs may lead to serious tissue damage and even amputation if administered into an artery rather than a vein.