Vascular Access PDF

# Vascular Access ## Locating Blood Vessels - Apply a light to moderate amount of pressure with the transducer probe, alternately relaxing the pressure, to discern health, size and appropriate target veins, and to discern veins from arteries, and sometimes major nerves. ## Visualizing Nerves - Ner...

# Vascular Access ## Locating Blood Vessels - Apply a light to moderate amount of pressure with the transducer probe, alternately relaxing the pressure, to discern health, size and appropriate target veins, and to discern veins from arteries, and sometimes major nerves. ## Visualizing Nerves - Nerves have similar acoustic impedance as the surrounding soft tissues; may or may not be easily visualized. - **Median nerve:** courses up the upper arm with the brachial artery and veins as a bundle. ## Reflection of Needle Tip - When the needle crosses the US beam it is seen as a bright white reflection. - Needles with echogenic features can be visualized better on US. - Direct the needle so needle tip can be visualized in the middle of the intended vein to be cannulated. - A bright white light does NOT always indicate the needle tip itself as this could also be the echogenic needle shaft. ## Alternative Vascular Visualization Technology - **Fluoroscopy:** Real-time radiographic imaging used as image guidance during CVAD insertion by qualified practitioners; allows the inserter to visualize the vascular pathway and enables them to manipulate the catheter to proper position. (stenosis, occlusion, kinks, sharp angle, and inadvertent entry into collateral pathways can be seen). ## CVAD Tip Confirmation Technology - **Electromagnetic tip navigation** - Specially manufactured stylet with magnets in the tip; is placed in or preloaded in catheter prior to insertion which communicates with a sensor that detects changes in the magnetic field as the catheter/stylet assembly is advanced to the general desired location based on external anatomic landmarks. - Designed to avoid gross malpositions of catheter tip. - Often used in conjunction with intravascular ECG or ECG/Doppler technology. - Requires post-placement chest X-Ray (CXR) if used independently of approved ECG or ECG/Doppler technologies. - **Intravascular ECG or ECG/Doppler (IV ECG)** - Electrocardiograms (ECG) display an interpretation of the electrical signal changes as the myocardium depolarizes and repolarizes, usually detected through electrically conductive electrodes placed on the patient's thorax which are connected by wires to an ECG monitor. This technique uses a saline column in the catheter or intra-catheter stylet that acts as an ECG electrode, replacing the traditional electrode usually placed on patient's right upper chest. A second electrode placed is placed on left upper chest and a third on left lower chest abdomen or leg. - Sinoatrial node initiates right atrial contraction, manifested as a "P" wave on ECG. - The reading on the ECG monitor reflects the intravascular electrode (the catheter tip) approaching the distal superior vena cava and right atrium and will show changes in the "P" wave as it moves through the SVC, and into right atrium. - Maximal P wave prior to deflection indicates that the catheter tip is in the proximal right atrium, at the Caval-Atrial Junction (CAJ). - Existing ECG or ECG/Doppler technologies may be challenged in determining tip location in patients who do not have an easily identifiable 'P" wave. (such as those with a pacemaker or a fib). A chest X-Ray must also be obtained to confirm tip location. - **ECG with Intravascular Doppler** - A stylet that has a doppler built into the tip in addition to the ECG lead, to determine the direction of blood flow i helps guide catheter towards the distal SVC. - Provides evidence of inadvertent arterial cannulation with the catheter. - Chest radiograph or other internal tip locating systems are currently used for identifying. ## CVAD Tip Location in the Absence of other Tip Location Technologies - **Posterior-Anterior (PA) position provides best image for catheter tip location** - Heart sits anterior in chest. - Less distortion. - Greater radiation energy. - Patient must be able to stand (non-portable technology). - CXR should be ordered specifically for CVAD Tip identification so settings can optimize catheter visualization. - **Anterior-Posterior (AP) position (back against the film as applies in portable CXR)** - Greater potential distortion. - Heart is further away from film: parallax effect with greater change in position. ## Cincinnati Triangle - 1-2 cm below atrial appendage. - 3-5 cm below carina. - **Carina** - Right mainstem bronchus. - Vertebral bodies. ## Factors That Interfere With Interpretation of Catheter Tip Location - Individual interpretation varies amongst providers. - Pulmonary edema caused by fluid overload, pneumonia. - Morbid obesity. - Portable CXR. - Pacemaker/AICD wires. - Other central venous catheters. - Spinal rods. ## X-Ray Settings for Viewing of Chest Structures vs. CVAD Tip Location - Supine to standing. - Arm adduction/abduction. - Respiratory Cycle. - Vein selection: Cephalic vs. Basilic. ## Oblique - Patient's torso is angled to enhance visualization of catheter tip, away from anatomic structures such as spinal processes, or artificial devices in chest such as wires, rods, or catheters. ## Lateral View - Can reveal malposition not always seen on PA or AP views. The most accurate in identifying catheters malpositioned in the azygos vein. - Radiographic anatomic landmarks to identify catheter tip in lower or distal one-third of superior vena cava, near juncture with the right atrium.