Arterial catheterization is a frequent procedure in intensive care settings and the operating room. This procedure involves the placement of a catheter into the lumen of a peripheral artery to facilitate hemodynamic monitoring and arterial blood sampling.
The arterial waveform was first described in 1847 by the German physiologist Carl Ludwig. More recently, the Seldinger technique of arterial catheterization has been adopted; this technique uses a guidewire to facilitate catheterization.
Arterial catheterization can be achieved via multiple anatomical sites; each has risks and benefits. However, practitioners must be mindful of procedural indications and contraindications, the proper preparation of equipment and personnel, and be skilled in insertion techniques. As with all invasive procedures, arterial catheterization may present complications, and personnel must be ready to intervene promptly to prevent unnecessary harm to the patient.
Anatomy and Physiology
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The arterial pulse may be palpated in the extremities and the neck and assists with locating the artery. Before arterial catheterization, the surrounding anatomy, adjacent landmarks, and the size and depth of the artery must be considered.
Upper Extremity Vasculature
The radial artery is a preferred catheterization site. The radial artery is palpated superficially in the thenar area of the wrist at the radiocarpal joint. The radial pulse is best felt slightly medial to the extensor tendons of the thumb.
The ulnar artery is opposite the radial pulse in the volar aspect of the wrist at the ulnocarpal joint. The ulnar artery divides into two branches, joining a similar division of the radial artery to form a rich collateral network known as the deep and superficial palmar arch. The ulnar artery is smaller and less readily palpable than the radial artery. Therefore, the ulnar artery is used less commonly for catheterization but may be accessed when other options have been exhausted.
The axillary artery rises to the superficial axilla as it courses through the pectoralis minor muscle, which is delineated best while the arm is abducted. This large vessel can be palpated slightly lateral to the belly of the pectoralis major muscle. The axillary artery and vein form a neurovascular bundle with the cords of the brachial plexus. Catheterization of the axillary artery requires abduction of the arm and is only used when peripheral options have failed. Advancement of the catheter into the subclavian artery provides a central pressure arterial waveform.
Catheterization of the brachial artery is not performed as there is a lack of collateral arterial flow; this increases the risk of ischemic injury to the distal upper extremity.
Lower Extremity Vasculature
The dorsalis pedis artery is readily palpated over the bony prominence of the navicular bone at the mid-dorsal aspect of the foot. The dorsalis pedis artery has ample collateral circulation, making it a preferred access site for the lower extremity. The operator accesses the artery by aiming directly at the pulsation as if performing venipuncture.
The posterior tibial artery is the other significant arterial supply to the foot. The posterior tibial artery runs posterior to the medial malleolus in a groove bordered by the Achilles tendon posteriorly. The posterior tibial artery is smaller in caliber than the dorsalis pedis artery and is at greater risk of occlusion.
The femoral artery is the main arterial supply to the lower extremity. The femoral pulse is a well-known anatomical landmark as the artery demarcates the inner one-third of the inguinal ligament from the outer two-thirds. The femoral artery is the single vascular trunk perfusing the lower extremity; no other major collateral arterial vessels exist for the lower extremity. Therefore, complete obstruction of the femoral artery may lead to lower limb ischemia with devastating consequences.
The superficial temporal artery is a branch of the external carotid artery. It may be palpated in the temporal area of the head anterosuperior to the ear.
The umbilical cord traditionally contains two umbilical arteries and one umbilical vein at birth. The umbilical stump typically involutes within the first few days of life. Before involution, however, the umbilical arteries are accessible; they are branches of the internal iliac arteries.
Arterial catheterization is frequently indicated in intensive care settings, where clinical situations often require continuous arterial blood pressure monitoring and frequent arterial blood sampling to analyze the partial pressure of oxygen, carbon dioxide, and serum pH. This monitoring is critical during the administration of vasoactive medications, as minute-to-minute evaluations are necessary to titrate these medications effectively.
Arterial catheterization allows for the systolic, diastolic, and mean arterial blood pressure to be readily displayed on the monitoring system using a transducer device attached to a noncompliant tubing system.
Other indications for arterial catheterization include cardiac catheterization and radiological interventional procedures, manual or automated exchange transfusions, plasmapheresis, continuous arterio-venous perfusion or hemodialysis, and extracorporeal membrane oxygenation. Some of these modalities require a surgical approach to arterial catheter placement.
Arterial catheterization is a procedure that carries the risk of serious complications. Prevention of adverse events is facilitated by understanding the contraindications to the procedure. These contraindications include but are not limited to:
- Peripheral or distal arterial insufficiency
- Peripheral arterial vascular diseases, including the small-to-medium vasculitides
- A lack of collateral circulation due to anatomical anomalies, such as the congenital absence of the ulnar artery
- Infection at the catheter insertion site
Clinical conditions that are not necessarily contraindications to arterial catheterization but require special consideration include hypercoagulable and anticoagulated states, burns, and surgical interventions at the insertion site.
All equipment, including an infection control bundle, must be assembled at the bedside before initiating arterial catheterization. These commercially-available bundled kits minimize procedure time and facilitate adherence to evidence-based best practices that minimize insertional catheter-related infections. While the content of kits varies by manufacturer, all include the appropriate-sized catheter and corresponding search needle, lidocaine, gauze, chlorhexidine solution, and sterile gowns, masks, and gloves.
The transducer, connecting tubing, and monitor cable system must be available before catheter insertion. The waveform obtained after connecting the arterial catheter to the monitor confirms successful placement in the lumen of the artery.
The placement of an arterial catheter requires at least one other helper in addition to the operator. This additional personnel will help with the non-sterile aspects of the procedure and the general circulating tasks. In addition, if the patient requires sedation during the procedure, another practitioner will administer and monitor that aspect.
Arterial catheterization is an invasive procedure that requires careful planning to minimize the risk of complications. Therefore, before initiating the procedure, the team is encouraged to use a checklist to review the necessary equipment and perform a "time out" procedure to verify the identity of the patient and the site of catheterization.
The proper aseptic preparatory technique includes hand washing, donning sterile gloves, cleansing the insertion area with chlorhexidine, and applying a sterile covering of the insertion site with a bio-occlusive tape. Once these tasks are completed, the puncture site may be determined by palpation, doppler auditory assistance, or ultrasound guidance.
Technique or Treatment
Before arterial catheterization, the operator must prepare the patient and locate the vessel via one of the methods discussed below. Once located, the operator may proceed with a direct puncture of the artery with the chosen device. The insertion angle will vary by anatomical site, and the degree of difficulty will be affected by the depth of the artery in the subcutaneous tissue.
The Allen Test
The Allen test is traditionally performed before catheterization of the radial artery. This test aims to provide assurance that the collateral ulnar arterial blood flow is sufficient to avoid distal ischemic injury. To perform this test, the radial and ulnar pulses are simultaneously occluded by manual palpation for 10 to 15 seconds or until blanching of the palm is noted. Then, the ulnar arterial occlusion is released. If the blanching resolves quickly, the patency of the ulnar artery is enough to perfuse the hand despite a complete or partial occlusion of the radial artery.
Doppler Auditory Assistance
In addition to palpating the arterial pulse, an auditory Doppler device can aid the operator in refining the point of entry for the access needle. This device may be beneficial in situations of low blood pressure when feeble pulsations make arterial pulse localization difficult.
Using ultrasound guidance during the catheterization of the radial artery has been associated with a high success rate. The number of attempts needed to achieve successful catheterization is significantly reduced using ultrasound guidance. This is particularly true in the infant and pediatric age groups, where repeated catheterization attempts increase the complication rate. In addition, the ultrasound-guided measurement of the internal arterial diameter may inform the choice of catheter size. This measurement may be particularly important in pediatric patients because of the different artery caliber expected in this population. Ultrasound-guided arterial cannulation has now become the standard of care.
The Seldinger technique allows the operator to gain access to the arterial lumen with the help of a guidewire. After localization of the pulse by palpation, doppler, or ultrasound guidance, the vessel is punctured with an introducer needle. Once pulsatile blood flow is detected, the guidewire is quickly inserted into the hub of the needle to gain access to the artery. Once sufficiently advanced, the introducer needle is removed. The opposite end of the guidewire is threaded into the sharp or distal end of the arterial catheter, sliding it until it is completely flush with the skin. The guidewire is removed and inspected for complete integrity of the tip. The Seldinger technique is particularly useful for the access of central vessels that run deeper into the extremity.
Catheter Over the Needle
The traditional technique of peripheral venous catheterization can also be used to access peripheral arteries that are more superficial and readily palpable. After localization, the artery is directly punctured with the catheter-over-the-needle device at the proper angle. Once arterial blood flow is detected, the operator slides the catheter over the needle in a forward motion before removing the needle.
Securing the Arterial Catheter
After the successful placement of the catheter and the connection of the transducer apparatus, the procedure team must secure the catheter to prevent accidental dislodgement and exposure to infection and minimize excessive motion of the adjacent joint that may interfere with the accurate monitoring. This procedure is also useful to increase the longevity of the catheter, avoiding a repeat procedure. Transparent adhesive dressings are preferred as they permit direct visualization of the insertion site. If the wrist is the site of insertion, the hand is kept slightly extended with a soft roll fixated between the dorsum of the wrist and a rigid board where the hand and forearm will be affixed. The connection tubing takes a loop around the thumb and is secured a second time to the forearm. To obtain an accurate blood pressure reading, the monitoring device must be set to "zero" while the transducer hub is leveled at the height of the atrium.
Arterial Catheter Monitoring
The positioning of the transducer and dampening of the monitoring system can affect the data obtained from arterial catheterization; interpretation is required. For instance, if the transducer is positioned too low relative to the catheter, the pressure value will be abnormally high. In contrast, if the transducer is positioned too high relative to the catheter, the pressure data will be too low.
Dampening of the system can result in falsely low or high systolic or diastolic pressure; this can be seen in the waveforms of the arterial line. If the arterial line has inadequate dampening, there will be an underestimation of the diastolic pressure and an overestimation of the systolic pressure. If the arterial line is overdampened, there will be an accurate diastolic pressure with a falsely-low systolic pressure. A clot or fibrin in the catheter tip can also result in an overdampened system.
The overall complication rate of arterial catheterization in adult patients ranges from 10% to 13%. Among the various complications, catheter-related infection and inflammation were the most common (61.8%). Other complications include mechanical complications (14.1%), embolic or thrombotic events (7.5%), and amputation for ischemic injury (0.6%). In addition, femoral artery catheterization has been associated with a higher risk of thrombosis than the radial approach. Higher complication rates are associated with critically ill patients, cardiac surgery, bone marrow transplantation, and hemodialysis.
Arterial catheterization in a pediatric patient can be daunting. Operators are often challenged with a blood vessel diameter of only 2 or 3 mm. Studies of the complication rate in the pediatric population are few; the largest retrospective analysis of more than 10,000 pediatric patients reported a complication rate of 10.3%) in pediatric patients. A young age of 1 to 4 months, catheter placement late in the hospital course, and systemic infections are additional risk factors for complications in the pediatric population.
Arterial catheterization and monitoring are, in many cases, the standard of care for critically ill patients. The procedure is prevalent in the medical and surgical intensive care units and the operating room in both the adult and pediatric populations. Arterial catheterization allows for continuous blood pressure and mean arterial pressure monitoring and facilitates frequent blood gas sampling.
However, complications, including catheter-related infections, loss of distal blood flow, and the availability of other modalities for hemodynamic monitoring, have decreased the overall frequency of arterial catheterization; the placement of arterial catheters should not be considered routine in the management of critically ill pediatric patients.
Nursing, Allied Health, and Interprofessional Team Interventions
It is vital to ensure that catheter patency is maintained via an infusion through the catheter at 1 to 3 mL/hour, with or without the use of a pressurized bag system. The infusate fluids commonly used are normal saline or normal saline with 1 to 2 units/mL of heparin. Studies indicate that using a heparinized solution does not reduce the risk of catheter thrombosis. Therefore, blood drawn from the arterial line for laboratory analysis should have some initial blood wasted to prevent laboratory errors; usually, 1 to 3 mL of waste is sufficient, depending on the age of the patient and circulating blood volume.
There have been previous reports of hyperglycemia secondary to the infusion of glucose-containing fluids through the arterial lines. In addition, limb ischemia and skin and tissue necrosis due to accidental infusion of medications through the arterial catheter have also been reported. Therefore, the arterial line should be clearly labeled to avoid these complications, and two nurses should thoroughly check the infusing fluids.
The perfusion distal to the catheter needs to be monitored by nursing staff, and the catheter should be removed if any concerns for ongoing impairment in perfusion arise.
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