Arterial Line

An arterial line is a thin tube (catheter) that a healthcare provider inserts in an artery to measure and monitor your blood pressure in real time. This is sometimes called “direct” blood pressure measurement or arterial catheterization. In certain situations, this method is more accurate than using other devices, like an arm cuff. Providers can also use the line to draw blood for testing.

Arterial lines aren’t a routine part of hospital care. Providers only use them in certain situations, like when you:

• Are critically ill
• Are having surgery and there’s a high risk of complications
• Need arterial blood gas testing

Arterial line placement lets your care team closely watch your blood pressure. The measurements are continuous, meaning there are no breaks in them. This lets providers notice any sudden changes — like a dangerous drop — and respond quickly. 

How does an arterial line work?

An arterial line captures pressure changes in your arteries. It’s able to do this because a catheter stays inside an artery — typically, one in your wrist.

Each time your heart beats, it pumps blood into your arteries. This makes your blood pressure briefly go up and then down again. The catheter detects this change in pressure. It sends signals through special tubing to a device called a transducer. The transducer converts these signals into a graph that your care team can read on a screen.

That graph is called a waveform. It looks like a series of lines that curve upward and then downward. It shows the changing pressure in your arteries for each heartbeat.

What happens during arterial line placement?

Your care team will set up your arterial line in a very clean (sterile) way. This involves placing sterile drapes around the access site that help block germs from getting in. Your care team will also wear masks and caps. All these things reduce your risk of infection.

If you’re awake, a provider will give you medicine called local anesthesia. This numbs the spot where the arterial line goes in, so you won’t feel pain there.

Your provider will choose the best artery for placing your arterial line. For most people, that’s the radial artery (in your wrist). It’s easy to access and has a low infection risk. Other options include the femoral artery (in your groin) or other arteries in your arm or foot.

Providers typically use ultrasound to guide arterial line placement. This lets them see your blood vessels in real time and make sure the catheter goes to the right spot.

The exact steps vary based on which artery your provider uses. For example, if they use your radial artery, they’ll turn your wrist upward and prop it up. In general, your provider will:

1. Numb a small section of the skin by injecting a local anesthetic
2. Use a needle to puncture your skin and access the artery
3. Guide a catheter into your artery (one end will stick out from your skin)
4. Use surgical tape to secure the end of the catheter against your skin so it won’t fall out

What are the risks of an arterial line?

The most common complications of arterial line placement are temporary and include:

• Pain, tingling or numbness at the insertion site
• Bruising at the site
• Minor bleeding

Serious complications are rare. These include:

• Infection at the insertion site, which may spread to your bloodstream
• Major bleeding
• Blood clots
• Air embolism
• Damage to your artery or nearby nerves

What can I expect after the test?

Arterial line monitoring may last days or even weeks. Your care team may change out the line every few days to lower the infection risk. They’ll remove it when you no longer need it and place a bandage over the site.

What type of results do you get?

You likely won’t see the results yourself. But your healthcare provider will review the graph that this test makes (waveform) and adjust your care as needed. The waveform helps them understand how well your heart is pumping out blood to your body.

When should I call a healthcare provider?

When you’re back home, call a provider if you have any signs of complications. These include:

• Fever or chills
• Skin irritation or color changes at the spot where the catheter went in
• Drainage or swelling at the site