Overview of Arterial Lines
Arterial catheterization is a common procedure done in intensive care units, emergency rooms, and operating rooms. It involves inserting a thin tube (or catheter) into a peripheral artery (an artery away from the heart) for different purposes. These include taking samples of arterial blood to check oxygen levels and acid-base balance, and for monitoring heart function by looking at patterns in arterial waveforms (up and down movements of a line on a graph indicating the rhythm and force of the heartbeat).
The concept of arterial waveforms was first identified by a German scientist named Carl Ludwig in 1847. A method called the Seldinger technique, which uses a guidewire (a thin wire used to guide the insertion of a catheter), was later introduced to make the procedure more efficient.
There are multiple places in the body where an arterial catheterization can be performed, each with its own advantages and risks. Healthcare providers must remember the suitable conditions for the procedure and those where it should not be done. Preparation of the equipment and personnel is key. Also, they need to be highly skilled in performing the procedure.
Like all procedures that involve entering the body, arterial catheterization might lead to complications. So, healthcare providers must be ready to quickly intervene to prevent any unnecessary harm to the patient.
Anatomy and Physiology of Arterial Lines
Arterial lines, which are life-critical tubes used in medical treatment, can be inserted into many different arteries depending on the circumstance. The radial artery in the hand and the femoral artery in the thigh are typically chosen because they are easy to access and the doctor can easily see the surrounding area before starting the procedure. Sometimes, the lines can be put into the brachial artery at the elbow, the dorsalis pedis artery in the foot, or the ulnar artery in the wrist. The doctor may use their hand to feel for the artery or use an ultrasound machine for accuracy.
It is important to confirm that there are other blood vessels that can keep blood flowing to the area if anything were to go wrong with the chosen artery. One way to do this is with an Allen test, which checks the blood flow in the hand.
The radial artery, which is a common choice for this procedure, begins at the elbow, branches from the brachial artery, and goes along the outer part of the forearm, providing blood to the hand. This artery can be felt on the inside of the wrist, slightly on the inner side of the extensors of the thumb. For this procedure, the optimal initial puncture is at the furthest part of the wrist, which is typically over the radial pulse at the beginning of the crease of the flexing wrist.
The ulnar artery, found on the palm side of the wrist, branches into two parts that join a division of the radial artery to form a network that supplies blood to the hand. This artery is smaller and harder to find than the radial artery and is less often chosen for catheterization, but might be considered when other options have been used or are not available.
The femoral artery, which starts at the hips, under the waistline, provides blood to the lower part of the body. Blocking this artery can lead to serious problems as there are no other major blood vessels to compensate. The femoral artery is usually accessed about 2.5 cm below the waistline for better control of bleeding.
The dorsalis pedis artery in the foot starts around the ankle, goes along the back of the foot and joins with another artery towards the space between the first two toes. This artery can be felt diagonally from the big toe towards the outside of the foot and is well suited for the procedure in children. Adults usually avoid this site as diabetics and peripheral artery disease patients might face complications.
Lastly, the posterior tibial artery, which supplies blood to the back of the foot, can be felt behind the ankle bone. This artery is smaller than the dorsalis pedis artery and therefore carries more risks if blocked.
The umbilical cord in newborns contains two arteries and is accessible before the stump of the umbilical cord falls off. In some rare cases, the superficial temporal artery in front and slightly above the ear has been used for procedures like heart stenting when there is severe disease in other arteries.
Why do People Need Arterial Lines
An arterial catheter, a thin tube inserted into an artery, can offer numerous advantages. It allows doctors to constantly monitor your blood pressure and gain easy access to your blood for testing. This can help the doctors in identifying irregular patterns on the heartbeat tracing and predicting how well you might react to fluids. This tube is especially valuable in settings like an intensive care unit or the operation theatre, where close monitoring is key.
Putting in an arterial catheter just for routine care is not recommended – it should only be done when it’s absolutely necessary – as it can lead to potential problems and might make future insertions more difficult.
In conditions where breathing is difficult due to low oxygen levels, an arterial line can enable doctors to calculate a vital figure known as the oxygenation index (OI). This figure helps in assessing the severity of lung disease. The OI is calculated using the average air pressure in your lungs divided by a figure that includes the amount of oxygen in your artery and the concentration of oxygen you’re inhaling. If this Information reveals an OI of more than 8, that suggests moderate lung disease; if it’s more than 16, the disease is severe.
Arterial catheters also allow continuous monitoring of your blood pressure. A device connected to the catheter can read your systolic, diastolic, and mean arterial blood pressure directly. This way of monitoring is more precise than using a cuff around your arm and can avoid potential errors. This becomes particularly important while giving medicines that impact blood pressure and require real-time monitoring.
Arterial catheters can also be used in various other procedures like heart surgeries, radiological interventions, blood transfusions, dialysis, and oxygenation therapies. However, it’s essential to remember that these catheters should not be used to administer medications as that could lead to severe complications, including numbness, excessive pain, and even loss of limb function or the entire limb.
When a Person Should Avoid Arterial Lines
Arterial catheterization is a procedure where a tube is inserted into an artery. This procedure can sometimes cause serious complications, especially if the tube is placed in certain locations in the body. To avoid these complications, it’s important for your doctor to understand the anatomy of your body as well as the reasons why the procedure may not be suitable for you.
Situations where the procedure might be avoided include:
- If you have poor blood flow to your arms or legs
- If you have diseases that affect the blood vessels in your arms and legs, including certain types of inflammation of blood vessels
- If you lack certain blood vessels due to birth defects, such as missing the ulnar artery, which runs along the inside of the forearm
- If there is an infection where the needle would be inserted (though this is less of a concern if the needle is to be placed in a part of the body further away from the center)
In some situations, the procedure might still be carried out but your doctor will need to think carefully about the risks. This is especially true if your blood has clots easily or is thin due to medications, or if you have burns or have had surgery where the needle would be inserted. In these cases, and others where there is a high risk, doctors usually do a simple test like the Allen test when they are using the radial artery found in your wrist. If doctors have doubts even after doing this test, they have other methods such as a special ultrasound or photoplethysmography (a test that measures changes in blood volume in the skin) to make sure the artery is open and the blood flow is good.
Equipment used for Arterial Lines
When your doctor needs to put a catheter (a thin flexible tube) into an artery, they typically use a pre-made kit of tools and supplies that are usually ready to use and sterile (free of any germs that might cause infection). These kits, full of everything your doctor might need, make the procedure quicker and safer.
Your doctor will need the following supplies to carry out this procedure:
- Clean gloves, gown, drape (a cloth to keep the procedure area clean), mask with eye shield
- A special sterile cloth called gauze
- Masks and towels to help keep everything clean
- Chlorhexidine or povidone-iodine solutions, which are used to clean and sterilize the skin
- 1% Lidocaine, a type of numbing medicine injected using a 25- to 27-gauge needle
- A small knife called a scalpel (No. 11 blade preferred)
- A needle driver, a tool to help hold and manipulate the needle
- A nonabsorbable suture, a type of thread that won’t dissolve in the body
- A sterile dressing that does not absorb any liquids
- Several technical components related to the catheter: a three-way stopcock, a pressure transducer kit, pressure tubing, intravenous (IV) tubing T-connector (a device that splits the IV line into two pathways)
- The catheter itself and a tool called a finder needle with an attached syringe
- A guidewire, a flexible wire used to guide placement of the catheter
Depending on where the catheter will be placed, the doctor may use different sizes of tools. For instance, if it’s in the wrist area (radial artery), they might use a different technique and corresponding equipment. Here, a 20-gauge (needle thickness) catheter with a 22-gauge introducer needle (a larger needle to guide the catheter) is used.
Babies and newborns generally need smaller equipment, a 22- to 24-gauge angiocatheter (another type of catheter). Adults and larger children may use a slightly larger tool, a 20-gauge peripheral artery catheter kit.
If the catheter is going into the femoral artery (located in the groin), it requires other types of equipment. This includes a larger 18-gauge needle, an introducer needle of similar size, and a longer catheter, among other things.
Your doctor may also use an ultrasound machine during this procedure, as it can help them accurately see where to place the catheter, reduce risks of complications, and make sure the right vessel is being inserted with the catheter. If they use an ultrasound, they will also need a particular type of probe and a kit to keep the probe sterile.
Once the catheter is in place, it’s connected to a monitor that provides a waveform. This waveform confirms that the catheter is properly placed in the artery.
Before beginning the procedure, all equipment, including a kit to prevent infections, need to be prepared and ready at your bedside. This is recommended to ensure a smooth and safe procedure.
Who is needed to perform Arterial Lines?
When a doctor needs to insert a small tube or ‘catheter’ into an artery (a blood vessel that carries blood away from the heart), they need extra help in the room. This help will come from an assistant who will take care of tasks that don’t need to be sterile (or germ-free). This assistant will also help by moving or ‘circulating’ around the room to do different tasks that need to be done. If you need to be put to sleep or ‘sedated’ during the procedure, another medically trained person will be there to give the medication and keep a watch on you.
Preparing for Arterial Lines
An arterial catheterization is a medical procedure that needs careful planning to lower the risks involved. It is strongly recommended that the medical team uses a checklist before the procedure starts to make sure everything is ready, including all necessary tools. The team should also pause for a moment or “take a time-out” to double-check the patient’s identity, the planned procedure, and the right spot for the catheterization.
The sterile or clean preparation technique for the procedure includes crucial steps. These steps involve washing hands thoroughly, wearing sterile gloves, cleaning the area where the catheter will be inserted with a special antiseptic called chlorhexidine, and securing the insertion site with a medical tape that can keep out germs. By following these steps, the medical team can choose the best place for the catheter through touching the area, listening to the blood flow with the help of a machine known as a doppler, or using ultrasound pictures to guide them. This ensures the procedure is done safely and effectively.
How is Arterial Lines performed
Although it seems like a complicated procedure, the methods used by medical professionals to insert an arterial catheter are actually very precise to ensure safety and comfort. The first thing that doctors do is dress in sterile clothing and then prepare their surgical tools. This includes ensuring their scanner is ready to view the procedure and locate the blood vessels.
The blood vessel where the catheter should be inserted is identified using several methods, including feeling the pulse, using an ultrasound machine to view the vessel, or relying on a Doppler auditory assistance device. The ultrasound machine is particularly handy, as it significantly reduces the number of attempts needed to insert the catheter, making the procedure more efficient. The Doppler auditory assistance device, on the other hand, is a great alternative when the patient’s blood pressure is low, making it hard to feel for the pulse.
Before inserting a catheter in the radial artery (located near the wrist), the professionals perform an Allen test. The test makes sure that enough blood is flowing through a nearby artery, the ulnar artery, that it will compensate if the radial artery is blocked during the procedure.
To make the procedure comfortable for the patient, the doctor usually injects a local anesthetic at the insertion site. Sometimes, the doctor might also make a small cut in the skin in cases where the patient’s skin is tough or the needle could make the insertion process difficult.
There are several techniques doctors use to insert the catheter, but the most common is the catheter-over-wire. This method, also known as the Seldinger technique, involves an introducer needle, a guidewire, and the arterial catheter. The doctor first punctures the artery with the needle, then inserts a guidewire into the needle. The needle is then removed, leaving only the guidewire. The arterial catheter is threaded into the artery over the guidewire, and once in place, the guidewire is removed.
After a successful insertion and connection to the monitoring device, it’s important to secure the catheter. This is done by wearing adhesive dressings, keeping the hand extended and immobilized. This fixation process helps to prevent dislodgement, reduce infection risks, and minimize movement that could disrupt monitoring. It effectively maintains the catheter and extends its lifespan, eliminating the need for reinsertion.
Possible Complications of Arterial Lines
In adults, about 10% to 13% of people might have some issues after having a procedure that involves inserting a tube into an artery, also known as arterial catheterization. These complications can vary based on where the tube is placed in the body. Techniques using ultrasound and strict cleanliness procedures can help lower many of these potential issues. Common problems may include pain, bruising, blood clotting, forming of abnormal blood-filled sacs, severe constriction of blood vessels, tearing of the arterial wall, creating an abnormal connection between an artery and a vein, or getting air or other particles into the bloodstream.
One of these issues, severe constriction of blood vessels, or vasospasm, has been found in up to 57% of patients according to older studies. This can cause symptoms like pain, lowered blood pressure, changes in the pulse, whitening of the fingers or hand, or loss of pulse or oxygen level in the affected arm or leg. Some studies from the 1970s suggested that giving certain medications before the procedure could lower the risk of this happening. But these strategies are not commonly used today during tube placements or for managing this issue if it does occur.
The most common problems related to the tube involve infection and inflammation, affecting about 61.8% of patients. This includes issues related to the mechanism of the tube (14.1%), blood clots or particle issues (7.5%), and major tissue damage requiring amputation (0.6%). The chances of complications can be higher in seriously ill patients, or patients who’ve had heart surgery, bone marrow transplants, or treatments for kidney failure.
More recently, doctors are placing these tubes into the radial artery in the wrist instead of larger arteries. This method lowers the overall risk of blood clots. However, it also has its own set of possible complications such as serious hand damage or temporary blockage of the radial artery. After the procedure and about 30 days later, complications can include particles blocking blood supply and tearing of the arterial wall. These risks could be even higher in patients with certain conditions that affect their blood vessels or blood clotting ability.
In children, arterial catheterization can present unique challenges due to their smaller vessel sizes of only about 2 to 3 mm. There is limited research regarding risks in children, but a large analysis reported a complication rate of 10.3%. Factors like age (1-4 months), placing the catheter later in their hospital stay, and having a systemic infection can also increase the risk of complications in children.
What Else Should I Know About Arterial Lines?
Arterial line placement is a common procedure for severely sick patients. This is a process where a tube is inserted into an artery, which are the blood vessels that carry oxygen-rich blood from your heart to the rest of your body. This procedure is often used in intensive care units and surgery rooms for both adults and children. One of the main benefits of arterial lines is that they can keep track of blood pressure around the clock. They are also useful for regularly drawing blood samples to check how well the lungs are transferring oxygen into, and removing carbon dioxide from, the bloodstream.
However, just like any medical procedure, placing an arterial line also has its risks. Installing a tube into an artery can possibly lead to infections or affect the blood supply to other parts of body. In addition, the way in which medical professionals monitor vital signs has improved over time, leading to other, less risky, strategies to measure blood pressure. As a result, doctors should be careful when considering arterial line placement as a routine procedure for children who are seriously ill.
