REVIEW OF LITERATURE
A central venous catheter (CVC), also known as a central line, central venous line, or central venous access catheter, is a catheter placed into a large vein. Catheters can be placed in veins in the neck (internal jugular vein), chest (subclavian vein or axillary vein), groin (femoral vein), or through veins in the arms (also known as a PICC line, or peripherally inserted central catheters). It is used to administer medication or fluids that are unable to be taken by mouth or would harm a smaller peripheral vein, obtain blood tests (specifically the “central venous oxygen saturation”), and measure central venous pressure.1,2
Reasons for the use of central lines include:
Long-term intravenous antibiotics
Long-term parenteral nutrition, especially in chronically ill persons
Long-term pain medications
Drugs that are prone to cause phlebitis in peripheral veins (caustic), such as:
Calcium chlorideChemotherapyHypertonic saline
Potassium chloride (KCl)
AmiodaroneVasopressors (for example, epinephrine, dopamine)PlasmapheresisPeripheral blood stem cell collections
DialysisFrequent blood draws
Frequent or persistent requirement for intravenous access
Need for intravenous therapy when peripheral venous access is impossible
BloodMedicationRehydrationMonitoring of the central venous pressure (CVP) in acutely ill people to quantify fluid balance1Central venous catheters usually remain in place for a longer period than other venous access devices, especially when the reason for their use is longstanding.Sterile technique is highly important here, as a line may serve as an entry point for pathogenic organisms. Additionally, the line itself may become infected with bacteria such as Staphylococcus aureus and coagulase-negative Staphylococci.3
CENTRAL LINE EQUIPMENT IN ORDER OF USAGE
1.syringe with local anaesthetic
2.Scalpel in case venous cutdown is needed
3.Sterile gel for ultrasound guidance.
4.Introducer needle with saline to detect backflow of blood upon vein penetration
Pneumothorax (for central lines placed in the chest); the incidence is thought to be higher with subclavian vein catheterization. In catheterization of the internal jugular vein, the risk of pneumothorax is minimized by the use of ultrasound guidance. For experienced clinicians,
the incidence of pneumothorax is about 1.5-3.1%. The (NICE) National Institute for Health and Clinical Excellence (UK) and other medical organizations recommend the routine use of ultrasonography to minimize complications.4
Vascular injuries that can occur during catheter placement include arterial injury, venous injury, bleeding, and hematoma. The use of ultrasound and operator experience greatly influence the incidence of vascular complications.5 Arterial puncture occurs in 4.2–9.3% of line placements, and is often easily recognized secondary to pulsatile flow, but recognition may be difficult in a hypotensive and critically-ill patient.6,7 If there is uncertainty of the punctured vessel, a single lumen catheter can be placed over the guide wire and connected to a pressure transducer to assess for venous waveforms.6 In the instance of an inadvertent arterial catheter placement, leaving the catheter in place and immediate removal with pressure, each carry separate risk. Prolonged arterial catheterization can result in thrombus, neurologic deficits, and stroke. Immediate removal of an accidental arterial catheter can result in uncontrolled hemorrhage,
pseudoaneurysm, and arteriovenous (AV) fistula formation; especially in patients who are treated with anticoagulatants or antiplatelet agents.6 Recent studies have demonstrated that leaving the arterial catheter in place with prompt repair carries less morbidity and mortality than catheter removal with pressure.8,9
Chest X-ray demonstrating a pulmonary artery catheter inadvertently placed via the right carotid artery into the thoracic aorta. Despite pressure waveform monitoring, erroneous placement was not noticed until a post-procedure chest was obtained. The catheter was removed immediately.
Follow-up carotid ultrasound was unremarkable for arteriovenous (AV) fistula or pseudoaneurysm. This patient had no residual complications as this complication was immediately recognized and managed 10
Hematoma formation has been reported in up to 4.7% of all catheter placements.7 Hematoma formation is often not life-threatening, but the pleural space and mediastinum are both potential spaces where hematoma may occur. However, such fluid collections can be significant sources of infection in critically-ill patients and may progress to abscess formation. Accumulation of blood in these spaces results in hemothorax and hemomediastinum and may require surgical intervention for image-guided (i.e., computed tomography (CT)) drainage. Oozing related to catheter placement can occur in patients with coagulopathies, and can often be controlled with pressure at the insertion site.7
The traditional approach entailed identifying the external landmarks (sternocleidomastoid muscle, clavicle,sternal notch, and cricoid ring) and palpating the CA pulse. At the level of the cricoid ring and at the apex ofthe triangle formed by the division of the sternocleidomastoid muscle and the base of the clavicle, a 21-gauge, 4-cm-long needle was inserted at a 30″ angle lateral to the CA and directed toward the ipsilateral nipple. This point lies approximately lateral to the intersection of the CA with a line between the mastoid process and thesuprasternal notch (fig. 1). The anesthesiologists use their left index and middle fingers to retract the pulsating CA. They identified the IJV puncture by the easy aspiration of dark venous blood from the vein through the needle. Using a standard Seldinger technique, a guidewire (0.018 inches in diameter, 40 cm long) was passed through the needle, followed by tissue dilation with a 5-French 8-cm-
long dilator and advancement of a heparin-coated polyurethane 4-French (1 %gauge), 8-cm (3 1/8 inch) double-lumen catheter (Cook Central VenousCatheter; Cook Critical Care, Bloomington, IN). Successful placement was confirmed by the easy aspiration of dark blood from the lumens of the catheter and by observation of the transduced atrial waveform on the monitor. The position of the central line was absolutely confirmed by chest radiography performed at the conclusion of surgery.11
The landmarks method (traditional method). A = mastoidprocess; B = sternal notch; C,D = carotid artery; Y = cricoid ring; X = point of needle insertion
ULTRASOUND GUIDED TECHNIQUE
Ultrasound technology has long been used in interventional radiology to guide percutaneous procedures at sites such as the kidneys, liver, arterial and venous circulation, pleural cavity, gallbladder and joints. Real-time ultrasound guidance of CVC insertion provides the operator with visualisation of the desired vein and the surrounding anatomical structures before and during the insertion. The advantages of ultrasound-guided central venous catheterisation include theidentification of the precise position of the target vein and the detection ofanatomical variants and of thrombosis within the vessel, together with theavoidance of inadvertent arterial puncture. Ultrasound guidance therefore hasthe potential to reduce the incidence of complications related to initial venouspuncture, which is the first stage of CVC insertion.
Operators need to be trained to use ultrasound-guided techniques. Training involves not only acquiring the necessary manual skills, but also having a basic understanding of ultrasound
principles and being able to interpret ultrasound images.12
Right neck central vein cannulation. The ultrasound probe is held so that each side of the screen displays ipsilateral structures.With the probe mark placed on the upper left corner of the image, the displayed structures will move in the same direction with the probe.
Ultrasound modalities used for imaging vascular structures and surrounding anatomy include two-dimensional (2D)ultrasound, Doppler color flow, and spectral Doppler interrogation.The operator must have an understanding of probe orientation, image display, the physics of ultrasound, and mechanisms of image generation and artifacts and be able to interpret 2D images of vascular lumens of interest and surrounding structures. The technique also requires he acquisition of the necessary hand-eye coordination to direct probe and needle manipulation according to the image display. The supplemental use of color flow Doppler to confirm presence and direction of blood flow requires an understanding of the mechanisms and limitations of Doppler color flow analysis and display. This skill set must then be paired with manual dexterity to perform the three dimensional (3D) task of placing a catheter into the target vessel while using and interpreting 2D images. Two dimensional images commonly display either the short axis
(SAX) or long axis (LAX) of the target vessel, each with its advantage or disadvantage in terms of directing the cannulating needle at the correct entry angle and depth.Three-dimensional ultrasound may circumvent the spatial limitations of 2D imaging by providing simultaneous realtime SAX and LAX views along with volume perspective without altering transducer location, allowing simultaneous views of neck anatomy in three orthogonal planes.13 Detailed knowledge of vascular anatomy in the region of interest is similarly vital to both achieving success and avoiding complications from cannulation of incorrect vessels.Ultrasound probes used for vascular access vary in size and shape. Probes with smaller footprints are preferred in pediatric patients. Higher frequency probes ($7 MHz) are preferred over lower frequency probes (5 MHz) because they provide better resolution of superficial structures in close proximity to the skin surface.
It is important to appreciate how probe orientation relates to the image display. Conventions established by the ASE(AMERICAN SOCIETY OF ECHOCARDIOGRAPHY) for performing transthoracic imaging of the heart, and more recently epicardial imaging, established that the probe indicator and right side of the display should be oriented toward the patient’s left side or cephalad.14 In these settings, projected images correlate best with those visualized by the sonographer positioned on the patient’s left side and facing the patient’s right shoulder. In contrast, the operator’s position during ultrasound-guided vascular access varies according to the target vessel. What is common for all vascular access sites is that it is essential for the operator to orient the probe so that structures beneath the left aspect of the probe appear on the left side of the imaging screen. Although probes usually have markings that distinguishes one particular side of the transducer, the operator must identify which aspect of the screen corresponds to the marking on the probe. These markings may be obscure, and a recommended practice is to move
the probe toward one direction or another while observing the screen or apply modest external surface pressure on one side of the transducer to demonstrate proper alignment of left-right probe orientation with image display.The probe used ultimately depends on its availability, operator experience, ease of use, and patient characteristics (e.g., smaller patients benefit from smaller probes)15
Various needle guides, used to direct the needle at the center of the probe (and image) and at an appropriate angle and depth beneath the probe. IJV, IJ vein. From Troianos CA. Intraoperative monitoring. In: Troianos CA, ed. Anesthesia for the Cardiac Patient. New York: Mosby; 2002.
Some probes allow the use of a needle guide, which directs the needle into the imaging plane and defined depth as viewed on the display screen (Figure 2).15
Arterial puncture during attempted venous cannulation with ultra-sound generally occurs because of a misalignment between the needle and imaging screen. It may also occur as a result of a through-and-through puncture of the vein into a posteriorly positioned artery. The first scenario is due to improper direction of the needle, while the latter occurs because of a lack of needle depth control. Needle depth control is also an important consideration because the anatomy may change as the needle is advanced deeper within the site of vascular access. The ideal probe should have a guide that not only directs the needle to the center of the probe but also directs the needle at the appropriate eangle beneath the probe (Figure 2). This type of guide compensates for the limitation of using 2D ultra-sound to perform a 3D task of vascular access. Vascular structures can be imaged in SAX, LAX, or oblique orientation (Figures 3A, 3B, and 3C). The advantage of the SAX view is better visualization of surrounding structures and their relative positions to the needle. There is usually an artery in close anatomic proximity to most central veins. Identification of both vascular structures is paramount to avoid unintentional cannulation of the artery.In addition, it may be easier to direct the cannulating needle toward the target vessel and coincidentally away from surrounding structures when both are clearly imaged simultaneously. The advantage of the LAX view is better visualization of the needle throughout its course and depth of insertion, because more of the needle shaft and tip are imaged within the
ultrasound image plane throughout its advancement, thereby avoiding insertion of the needle
beyond target vessel.15
Figure 3. Two-dimensional imaging of theright IJ vein (IJV) and CA from the head ofthe patient over their right shoulder. (A) SAX, (B) LAX,
oblique axis. SAX imaging displays the lateral-right side of the patienton the right aspect of the display screen and the medial structures on the left aspect of the display screen. LAX imagingdisplays the caudad structures on the rightaspect of the display screen and cephalad structures on the left aspect of the display screen. If the transducer is rotated counterclockwise about 30 –40 degrees, obliqueimaging displays more lateral-right caudad structures on the right aspect of the display screen, while more medial-left cephalad structures are on the left aspect of the display screen.
One operator can usually perform real-time ultrasoundguided cannulation. The nondominant hand holds the ultrasound probe while the dominant hand controls the needle. Successful cannulation of the vessel is confirmed bydirect vision of the needle entering the vessel and withblood entering the attached syringe during aspiration. The probe is set aside on the sterile
field, the syringe removed,and the wire is inserted through the needle. Further confirmation of successful cannulation occurs with ultrasound visualization of the guide wire in the vessel. Difficult catheterization may benefit from a second person with sterile gloves and gown assisting the primary operator by either holding the transducer or passing the guide wire.
Morphologic and anatomic characteristics can be used to distinguish a vein from an artery with 2D ultrasound. For example, the IJ vein has an elliptical shape and is larger and more collapsible with modest external surface pressure than the carotid artery (CA), which has rounder shape,thicker wall, and smaller diameter (Figure 4). The IJ vein diameter varies depending on the position and fluid status of the patient. Patients should be placed in Trendelenburg position to increase the diameter of the jugular veins15,16 and reduce the risk for air embolism when cannulating the SC vein, unless this maneuver is contraindicated. A Valsalva maneuver will further augment their diameter16 and is particularly useful in hypovolemic patients. Adding Doppler, if available, can further distinguish whether the vessel is a vein or an artery.
In 1996 nearly 20 years ago, a meta-analysis of ultrasound guidance for central venous catheter placement concluded that “compared with the landmark technique for placement of internal jugular and subclavian central venous catheters, ultrasound guidance significantly increases the probability of successful catheter placement, significantly reduces the number of complications encountered during catheter placement, and significantly decreases the need for multiple catheter placement attempts.”17 Ultrasound guidance for central venous catheter placement has been endorsed as a key safety measure by both the Agency for Healthcare Quality and Research18 in the United States and the National Institute for Health and Care Excellence19 in Great Britain for more than a decade. Guidelines from 14 professional societies in addition to the American Institute of Ultrasound in Medicine have definitively
recommended that ultrasound be used for central venous catheter placement, particularly when an internal jugular approach is used.20,15 The strength and breadth of these recommendations and the length of time that they have been in place suggest that ultrasound guidance for internal jugular and femoral central venous catheter placement should now be standard practice 21
Cannulation Technique for Pediatric Patients IJ Vein
The most frequently accessed central vein using ultrasound in pediatric patients is the right IJ vein. Ultrasound allows easy visualization of the vessel, demonstrating its position, its patency and the presence of thrombus.22 Hanslik et al.23 demonstrated a 28% incidence of deep venous thrombosis in a series of children with short-term central venous line placement. This is problematic in children requiring frequent central venous access, as in the pediatric cardiac surgical population. The council recommends real-time use to derive the most benefit from ultrasound guidance. Liver compression may be used to increase IJ size in
pediatric patients.24 Alternatively, the Trendelenburg position can be used. Sterile probe is placed transverse to the neck, creating a cross-sectional view of the vessels. The right IJ vein should lie lateral to the right CA and be easily compressible by the ultrasound probe (Figure 4). The neck should be scanned with ultrasound to identify the access point that is most conducive to cannulation of the vein, while avoiding the artery. This may or may not be the same point identified with landmarks alone. The probe should also be positioned to allow the needle to enter
at an angle away from the carotid . 15
Figure 4. Vessel identification. Right IJ vein (top) and CA (bottom) in SAX and LAX orientation. Slight external pressure compresses the oval-shaped vein but not the round-shaped artery
Shorter needles and a more superior entry point may reduce the risk for pleural or great vessel puncture, which is a particularly important concern for pediatric patients. The cannulating needle or catheter should be observed entering the vessel. The technique of observing vessel entry in real time is critical to avoid the complications associated with the landmark-guided techniques. The guide wire is inserted using the Seldinger technique, and its presence within the vein lumen and its absence within the artery are confirmed in two image planes, as demonstrated
in Figure 15, before dilation and placing the central venous catheter15
Figure 15. The guide wire (arrow) is demonstrated entering the right IJ vein, in SAX (A) and LAX (B) views..
Percutaneously inserted catheters have a substantial risk of displacement due to the inherent restlessness of young children. One of the main advantages of tunneled totally implanted ports is the low to negligible risk of displacement of the central part of the catheter 25,26
In adults, the jugular veins are frequently used as sites for CVC insertion. Although, in this population, subclavian vein catheters have the lowest risk of infection, the insertion procedure in the jugular veins is relatively easy and has a lower risk of mechanical complications, especially pneumothorax. Therefore, the jugular vein is frequently used for venous access when short (_5 days) indwelling times are expected. Consequently, in children with a different anatomy
and lower body weight, the increased risk of pneumothorax probably outweighs the risk of infections, especially with short indwelling periods. Hence in sedated children with a controlled airway, the jugular vein is the is the preferred site for percutaneous CVC access.27
Percutaneous insertion of CVCs can be achieved through venipuncture or via surgical procedures. In contrast to adults, where CVCs can usually be inserted under local analgesia, children often require general anesthesia for jugular and subclavian access, whereas mild to moderate sedation may suffice for access of the femoral vein. The most frequently occurring mechanical complications associated with access of the jugular or subclavian veins in both children and adults are pneumo-, hydro-, or hematothorax and arterial puncture. Less frequent complications include the superior vena cava syndrome, cardiac tamponade, severe cardiac arrhythmias, hematomas, persistent bleeding, air embolism, and catheter embolism 27. The risk of these complications is low, but the consequences may be severe 27,28,29.Visualization (by ultrasound or fluoroscopy) can facilitate CVC insertion and positioning of the tip 30 In many centers, CVC position and occurrence of complications are verified by a chest radiograph following CVC insertion. Although few data are available, we recommend performing post procedural radiographs to assess complications and catheter position at least in young children.31
Catheter-related thrombus formation occurs at the CVC tip or at the site where the CVC penetrates the vessel wall. The fibrin sheath formed at these sites can subsequently “grow” alongside the catheter. Blood is a more or less ideal culture medium for bacteria; therefore, an indwelling CVC is an important risk factor for hematogenous infection and spread.31. Thrombus formation can lead to various other mechanical complications such as blockage of the lumen, circulatory obstruction, and thromboembolism 32.For prevention of thrombus formation intermittent or continuous flushing of the CVC with an anticoagulant (usually heparin) is a widely accepted method for thrombosis prophylaxis 33,34.For diagnosis of thrombosis doppler-ultrasound is our method of choice when catheter-related thrombosis is suspected.31
The use of full sterile barrier precautions while inserting a CVC has been found to reduce the risk of Cathater Related Infections in adults, at least in immunocompromised patients 35,36 No specific literature in pediatric patients is available, but it seems sensible to use similar procedures in this group. Chlorhexidine 2% for skin disinfection has been found to be superior to other antiseptics such as iodine or alcohol 37. The immaturity of the immune system (as is the case in the first 4–5 years of life), differences in the degree and type of skin pathogens, and the way in which a patient’s immune system responds to the presence of a CVC as “foreign body” are factors that could influence this risk.31
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