An arterial line, or 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 the blood pressure real-time (rather than by intermittent measurement), and to obtain samples for arterial blood gas measurements. It is not generally used to administer medication. Since many injectable drugs used in intensive care and anesthesia, such as sodium pentothal, may lead to serious tissue damage and even amputation if given in an artery the arterial line must be clearly marked to avoid accidental intra-arterial injection of intravenous drugs.
An arterial line is usually inserted in the wrist (radial artery); but can also be inserted into the elbow (brachial artery), groin (femoral artery), foot (dorsalis pedis artery) or the inside of the wrist (ulnar artery). Any artery that isn't an end-artery can theoretically be used but in practice it's the arteries mentioned above that are used. A golden rule is that there has to be collateral circulation to the area affected by the chosen artery so that peripheral circulation is maintained by another artery even if circulation is disturbed in the cannulated artery.
Insertion is often painful; however an anesthetic such as lidocaine can be used to make the insertion more tolerable and additionally help prevent vasospasm thereby making cannulation of the artery somewhat easier.
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