Arterial Line Care Basics

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The following course content

Introduction   

Arterial cannulation is an invasive procedure for clients requiring continuous hemodynamic or frequent laboratory and arterial blood gas monitoring. Approximately eight million arterial catheters are placed annually in the United States. The incidence of complications from arterial cannulation ranges from 10% to 13% in adult clients (1, 2). These complications contribute to adverse outcomes and prolonged intensive care stays.  

In critical care settings, arterial cannulation is commonplace, and nurses require specialized training and an understanding of arterial lines. The ability to monitor hemodynamic status from moment to moment allows the healthcare team to make timely decisions and interventions for critically ill clients. This course aims to deliver a basic understanding of arterial lines from insertion (cannulation) to removal to equip nurses to confidently care for clients with arterial lines and develop their critical care skills.  

Indications and Contraindications 

Arterial cannulation or catheterization is the process of inserting a tube into an artery (1,3). Arterial lines are commonplace in critical care settings. However, not every client in critical care settings requires an arterial line. Arterial lines are indicated for clients requiring close monitoring of hemodynamic status, such as a client receiving vasoactive drips. Another indication is for clients requiring frequent laboratory monitoring, such as frequent arterial blood gasses (ABGs) in an unstable intubated client. Arterial lines allow for continuous monitoring, which is critical in clients requiring careful titration of vasoactive medications (e.g., epinephrine, norepinephrine) and frequent assessment of respiratory status through ABGs to titrate mechanical ventilation settings (1, 3).  

The contraindications for arterial line cannulation include infection at the insertion site, absent or compromised collateral circulation, peripheral arterial vascular insufficiency, and peripheral arterial vascular diseases. When considering arterial cannulation, the healthcare team should be mindful of clients with coagulopathies or receiving anticoagulant medication (1, 3).  

Cardiac Cycle and Arterial Waveform  

This section briefly reviews the cardiac cycle in relation to the arterial waveform, which is seen on the monitor. An arterial line setup provides continuous arterial blood pressures by converting mechanical pressure into a waveform and numeric data. It is vital for any nurse caring for a critically ill client to analyze and interpret the arterial pressure waveform.  

The aortic valve opens during systole. During this phase, blood is rapidly ejected from the left ventricle into the aorta. When viewing the arterial waveform, the nurse will see this systole as an upswing followed by a downward turn. Lock the term dicrotic notch into your critical care vocabulary. It is a feature of the arterial waveform that is important to identify when determining the phase of the cardiac cycle and when assessing the quality of the arterial waveform.  The dicrotic notch occurs about midway on the downward slope of the arterial waveform. This notch marks the start of the diastole, which is when the aortic valve closes. The remainder of the downward slope reflects the diastolic blood flow into the arterial tree. Abnormal heart rhythm and valvular anomalies have an abnormal arterial waveform. Over and underdamping also impacts the waveform (3). For image, visit: [Figure, Arterial Waveform Contributed by Y Nguyen, MD] – StatPearls – NCBI Bookshelf 

Arterial Line Insertion 

This section provides an overview of arterial line insertion sites and techniques and an overview of the equipment required and their purposes for the system setup. Arterial catheter insertion may be a planned procedure where the nurse has time to gather equipment and set up the system. There will be instances where insertion occurs during an acute change in status, so the nurse needs to be proficient in understanding the equipment required, basic insertion steps, and the system setup. 

Insertion Sites 

Arteries of the upper and lower extremities are used as sites for arterial line cannulation. The radial and femoral arteries are preferred because they are easily accessed, allowing for a more thorough evaluation of the anatomy and landmarks (1). Additional upper extremity insertion sites include the ulnar, axillary, and brachial arteries. Lower extremity arteries used for cannulation include the dorsalis pedis and posterior tibial. The superficial temporal artery is a branch of the external carotid artery; however, it is not commonly used for arterial line placement. The umbilical arteries are an option during the first few days of life before the umbilical stump involutes. These two arteries are branches of the internal iliac arteries (1, 3).  

Insertion Technique 

Arterial cannulation is an invasive procedure completed only by a certified provider. An additional healthcare team member, including nursing, works alongside the provider to ensure sterile technique is followed (1, 2). Since arterial catheterization is invasive, a checklist should be available to ensure all the equipment is at the bedside. A “time-out” should also be followed to confirm the client’s identity, the intended procedure, and the correct catheterization site, which the provider must identify before starting the procedure (1).  

Several medical societies recommend ultrasound (US)-guided arterial cannulation; however, current guidelines do not state recommendations for routine use (4). The more recent studies focusing on US-guided arterial cannulation versus palpation alone concluded that the US-guided technique increases the first-attempt success but with little difference in hematoma formation or the duration of attempts compared to palpation alone (5,6). The provider can utilize the traditional palpation technique by identifying anatomic landmarks and palpating for arterial pulsation. Doppler auditory assistance can help more accurately identify the entry point after palpation (1). When the provider elects to use US-guided placement, the nurse helps ensure that the US does not break sterile technique by checking that a sterile cover for the US probe and sterile conductive medium are available (4). 

Arteries are essential because they supply oxygenated blood to the body. Ensuring collateral circulation in the area supplied by the chosen artery is important. Arterial thrombosis can occur as a complication of arterial lines. If arterial thrombosis develops, collateral circulation – peripheral circulation provided by another artery – is crucial to prevent permanent damage to the limb (2). The modified Allen test is assessed before radial or ulnar artery catheterization to ensure adequate collateral ulnar arterial blood flow. The following steps perform this test.  

1. Compress the radial and ulnar pulses simultaneously by palpation for 10 to 15 minutes. The examiner should note the presence of palmar pallor.  

1. Release the compression of the ulnar artery, but continue to compress the radial artery.  

1. Observe for return to baseline color within ten seconds.  

1. The test should be repeated on the same hand, but pressure should be released from the radial artery (7).  

The materials required for arterial catheter placement are usually bundled in sterile, pre-packaged kits. The catheter-over-wire technique is the primary approach for arterial catheterization. A guidewire allows the operatory to gain access to the arterial lumen. The guidewire is removed when the catheter is placed into the vessel. The catheter-over-needle technique is similar to the guidewire, as the needle helps access the vessel lumen and is removed once the catheter is in place. Another technique that is strongly discouraged is arterial cutdown. This technique should only be used as a last resort (1).  

Securing the Arterial Catheter 

The arterial catheter must be secured (e.g., tape or suture) and covered with a transparent dressing to prevent accidental dislodgement, reduce the risk of infection, and minimize motion (1, 2). Excessive motion of the adjacent joint interferes with accurate monitoring. The adjacent joint is the wrist for radial artery catheterization, so optimal positioning is the palm up and the hand slightly dorsiflexed (envision Spiderman releasing a web from the wrist!).  The positioning is maintained with a soft roll between the dorsal wrist and a rigid board. When the soft roll and board are positioned, they can be fixed with non-shearing tape on the hand and forearm (1).  

Arterial Line Setup 

Before beginning the procedure, the arterial line setup should be completed to connect immediately to the arterial catheter upon insertion. It is essential to use the correct equipment and procedure when setting up the arterial line to ensure accuracy in monitoring and preventing complications. This section will highlight the equipment that is part of the arterial pressure monitoring setup and its function.  

Pressure tubing used for arterial pressure monitoring is 48 inches long and is a non-compressible, saline-filled tubing connected from the arterial catheter to the transducer. The tubing’s length, diameter, and rigidity are critical to ensure proper readings. The pressure tubing reduces damping, allowing the mechanical pressure oscillations to reach the transducer. The transducer converts the pressure from the arterial system into an electrical reading. The electrical reading is the waveform and numeric blood pressure transmitted via a cable connected from the transducer to the monitor (2).  

A three-way stopcock is positioned at the transducer to zero the transducer and flush the system. The transducer is placed on a roller plate attached and affixed usually onto an IV pole. The roller plate allows the transducer to be positioned correctly at the heart level, specifically at the fourth intercostal space on the mid-axillary line. This position is called the phlebostatic axis (1, 2).  

Standard intravenous tubing containing a roller clamp and spike connects a 500-milliliter normal saline bag within a pressure bag to the transducer. The pressure bag must be pressurized appropriately (greater than 300 mmHg) to ensure the appropriate forward flow of normal saline, three to five milliliters per hour in adults, to help prevent thrombus formation (2). The normal saline bag is used to prime the entire system, including the transducer, pressure tubing, and any additional stopcocks and caps. Some arterial line systems contain an accordion and vamp, which are used to collect blood samples without having to waste blood. The accordion and vamp are equally important to prime because air can be injected from these sections if not properly primed.  

Alterations in Arterial Waveforms  

External pressures, position changes, and damping influence the arterial pressure readings. Generally, the bedside nurse zeroed the transducer once per shift and for questionable readings. The transducer is zeroed by opening the stopcock to the atmosphere. The zero button is pressed on the monitor to indicate the zero reference pressure. The purpose of zeroing the transducer is to counteract the impact of external pressures, including atmospheric pressure, on the monitoring system (2). If the accuracy of the arterial pressure reading is in doubt, it is reasonable to zero the transducer. Another factor to consider when the blood pressures are questionable is the transducer’s positioning.  

When a client is repositioned, it is essential to relevel the transducer to the level of the phlebostatic axis. When the transducer is positioned too low, there will be a falsely elevated blood pressure (2). When the transducer is positioned too high, the transducer will register an abnormally low blood pressure. This occurs because the weight of the fluid within the tubings exerts hydrostatic pressure on the transducer, affecting blood pressure readings (1).  

Along with dicrotic notch, the following two terms should also be locked into the vocabulary for nurses managing arterial lines – damping and square wave test. Damping is the amount of resonance in the system that affects the systolic and diastolic blood pressure readings; however, the mean arterial pressure remains accurate. The nurse can recognize if the system is over or under-damped by analyzing the arterial waveform on the monitor when performing the square wave test.  

The square wave test is performed by a fast flush from the stopcock at the transducer; a square wave appears on the monitor. An optimally damped system is evidenced by one oscillation before returning to baseline and an obvious dicrotic notch (1, 2). If the nurse or healthcare team questions the arterial blood pressure, consider the impact of under or overdamping on the system.  

In an underdamped system, the square wave test results in two or more oscillations before returning to baseline. The nurse may observe a deep dicrotic notch in an underdamped system (1,4). An underdamped system occurs from excess resonance. Underdamping overestimates systolic blood pressure and underestimates diastolic blood pressure, but the mean arterial pressure remains unaffected (1). Underdamped waveforms are caused by artifact, excessively stiff tubing, defective transducer, hypothermia, tachycardia, or dysrhythmia (2,4).  

The square wave test results in less than one oscillation before returning to baseline in an overdamped system. The presence of a dicrotic notch is also unclear. In an overdamped system, the systolic pressure is underestimated, and the diastolic blood pressure is overestimated, but again, the mean arterial pressure is unaffected (1,4). An overdamped system is caused by low infusion bag pressure, loose or open connection, clots or kinks in the tubing, or air bubbles in the tubing (2,4). 

Most monitors have an autoscale feature. However, if the monitor is not autoscaling appropriately or the settings are altered, the waveform can appear over- or underdamped (3,4). Additionally, waveforms vary slightly depending on the location of the arterial catheter. So, consider the location of the client’s arterial catheter when interpreting the arterial waveform. For image, visit: [Figure, Damping of Arterial Pressure Waveform Contributed by Y Nguyen, MD] – StatPearls – NCBI Bookshelf  

Nursing and Arterial Line Management 

There are complications associated with arterial cannulation. Using ultrasound for arterial catheterization placement and following sterile technique during placement are protective factors in preventing complications. The more common complications include local pain and paresthesia, hematoma, and minor bleeding (4). Less common but more severe complications include embolism from air or thrombotic contents, vascular thrombosis and occlusion, vessel injury, pseudoaneurysm formation, and local nerve injury (4, 8). Catheter-related bloodstream infections are higher for femoral artery cannulation than radial artery cannulation. Unintentional injuries can result from intra-arterial medication injection and tubing disconnection, which can lead to major blood loss. Nurses must ensure no disconnections within the arterial line tubing, all stopcocks are correctly positioned, and all caps are on (2,4). 

Nurses must perform frequent, usually hourly, site assessments to evaluate for signs of infection, impaired perfusion, and vasospasm. The signs of infection include erythema, pain, fever, and discharge from the site. These should be immediately reported to the provider. The arterial catheter dressing should be changed weekly or if the integrity of the dressing is compromised (2). Arterial line dressing changes are performed weekly or based on specific institutional policy and adhering to sterile technique. 

Thumb and hand perfusion should be closely monitored in clients with radial artery catheterization to assess if the bloody supply is compromised. Assessing perfusion status includes noting the skin temperature, color, capillary refill, and client reports of limb pain or paresthesias (1, 2). Vasospasm is evidenced by pain, decreased blood pressure, blanching fingers or hand, and loss of pulse of O2 saturation signal in the limb with the arterial catheter (1). Intraarerially injected papaverine can provide relief of vasospasm caused by arterial catheter placement (9).  

The nurse should document the dressing status, date of dressing change if performed, insertion site assessment, and neurovascular checks (2). The arterial catheter must be covered with a transparent dressing to visualize the site easily.  

Nursing should ensure the line is completely primed with normal saline to prevent air embolism and ensure the pressure tubing is optimally damped. Normal saline is the standard to maintain the patency of the arterial catheter. A review of randomized control trials determined that normal saline administered at a rate of three milliliters per hour is as effective as one to two units of heparin in saline (10). A study published in 2024 also concluded that normal saline is as effective as heparinized saline in maintaining line patency in pediatric clients with arterial catheters. Additionally, normal saline is safer and more cost-effective (4, 11). 

The nurse must label the arterial line to prevent accidental medication injection into the arterial circulation. Significant complications, including tissue ischemia and possible limb amputation, occur when the inadvertent injection of medication into the arterial line. Not all medications inadvertently injected into the arterial line result in complications. The mechanism of injury is not fully understood, but it is thought to result from drug crystallization or direct endothelial injury, which leads to thrombosis, tissue damage, and limb ischemia (12).  

One of the indications for arterial lines is for clients requiring frequent laboratory blood samples, such as clients requiring hourly ABGs. This course did not cover the specific steps in collecting a blood sample from an arterial line because of the varying setups. The key considerations for any system set-up are collecting the proper amount of waste to prevent inaccurate results, properly cleaning access sites, minimizing accesses to prevent line-associated infection, and ensuring all stopcocks and caps are correctly positioned to avoid blood loss (2).  

Prolonged arterial catheterization is associated with a higher risk of complications. Nurses should discuss with the healthcare team when it is appropriate to remove the arterial catheter. Trained nurses can remove arterial catheters. Before removing the arterial line cannula, the nurse should assess for any concerns with coagulation status. If there are concerns, the nurse should address them with the provider before removing due to the risk of bleeding. The nurse should apply direct pressure to the site immediately after removing the arterial cannula, usually up to 15 minutes. This is done to ensure hemostasis is fully achieved (2). The nurse should also assess whether the catheter is intact to ensure no fragments are retained.  

Practice Gaps 

A study published in 2023 appraised the quality of guidelines for peripheral arterial catheters. The appraisal concluded that guidelines for managing arterial catheters scored poorly for the rigor of guideline development, applicability, and stakeholder involvement.  Many current recommendations for arterial catheterization management are derived from recommendations for central venous catheters or peripherally inserted central catheters, particularly recommendations on preventing catheter-related bloodstream infections in arterial catheterizations (13).  

Conclusion

Arterial line management is reserved for nurses who receive specialized training. While arterial lines are commonplace in critical care settings, they are not without risks. Diligent assessment, proper arterial line set-up, and understanding arterial waveforms are essential in preventing complications and recognizing clinical changes requiring prompt intervention.    

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