An intravenous line (IV) is a small, flexible catheter inserted into a blood vessel to administer fluids, medications, or nutrients. This method allows for the rapid and effective distribution of therapeutic agents throughout the body. For routine patient care, IVs are always placed into a vein, not an artery. The distinction between these two vessel types separates a standard medical procedure from a medical emergency.
Understanding Venous Access for IVs
Veins are the preferred vessels for standard intravenous access because they are part of a low-pressure system carrying deoxygenated blood back toward the heart. This low pressure makes veins less prone to severe bleeding after being punctured. Veins are also often more superficial, making them easier to locate and access.
The most common sites for peripheral IV placement are the veins in the hands and arms, though they can also be placed in the feet or the scalp in infants. The procedure involves a professional locating a suitable vein, cleaning the insertion site, and guiding the flexible catheter into the vessel. Once secured, the needle is withdrawn, leaving the tube in place for continuous or intermittent therapy.
The Risks of Arterial IV Insertion
Inserting a routine IV into an artery, even accidentally, poses severe risks due to the distinct anatomy and function of these vessels. Arteries are thick-walled, muscular vessels that carry oxygenated blood away from the heart under high pressure. Puncturing an artery can lead to vigorous, pulsatile bleeding that is difficult to stop and requires sustained pressure.
The primary danger of administering fluids or medication into an artery is the potential for profound tissue damage in the limb. An accidental intra-arterial injection can cause intense pain and lead to arterial spasm, which constricts the vessel. This spasm, coupled with the potential for certain medications to precipitate, can block blood flow to the tissues.
The resulting lack of oxygen and nutrients quickly causes tissue death, known as ischemia. If this complication is not immediately treated, it can progress to gangrene and may require amputation. The high pressure within the artery also makes continuous infusion difficult, potentially forcing blood and medication back out of the catheter.
Specific Uses of Arterial Lines
While standard IVs are strictly placed in veins, a specialized catheter known as an arterial line (A-line) is intentionally placed into an artery. These lines are not used for routine fluid or medication infusion, as that would carry the severe risks previously described. Arterial lines serve a highly specific monitoring function and are reserved for patients in critical care settings, such as intensive care units (ICUs) or operating rooms (ORs).
The main purpose of an A-line is to provide continuous, real-time blood pressure monitoring, which is more accurate than intermittent readings from a blood pressure cuff. The line constantly transmits the pressure within the artery to a monitor, allowing the medical team to observe the patient’s hemodynamic status. Arterial lines also provide easy and frequent access for drawing arterial blood samples to test for blood gases, measuring oxygen and carbon dioxide levels. Common insertion sites include the radial artery in the wrist or the femoral artery in the groin.