An arterial line is a thin tube placed into an artery so the care team can watch your blood pressure continuously and draw arterial blood samples without repeated needle sticks. It gives real-time, beat-to-beat blood pressure readings, which is useful during surgery or critical care when blood pressure can change quickly.

It is most often placed in the radial artery at the wrist because it is easy to reach and has collateral blood flow, which helps protect the hand. Other common sites are the brachial and femoral arteries.

The line is connected to tubing, a fluid-filled transducer, and a monitor. The monitor shows the arterial waveform and pressure numbers. This helps the team guide treatment, including fluid and blood pressure medicine.