Stand at the patient’s side, ipsilateral to the target vein. To identify landmarks with ultrasonography, place the probe just proximal to the insertion site. Ensure that the image that appears on the ultrasound screen is oriented correctly by aligning the probe marker with the marker on the screen.
Place the transducer perpendicular to the clavicle, just inferior to the midportion of the clavicle, with the orientation marker directed cephalad. A transverse, or short-axis, image of the clavicle, subclavian vein, and subclavian artery should be visualized on the ultrasound screen. The vein and artery can be distinguished either by assessing their compressibility or by using color-flow Doppler imaging to reveal pulsatility or nonpulsatility. The transducer should be slowly moved 1 to 2 cm toward the shoulder to obtain the best view of the subclavian vein. It is important to note that the lung lies inferior and posterior to the vessel; the pleura can be recognized as an echogenic linear structure below the subclavian vein.
Position the transducer so that the subclavian vein is near the center of the ultrasound image. Gently palpate the skin to confirm that the intended puncture site is aligned with the center of the ultrasound transducer. The approximate depth of the subclavian vein and pleura can be determined by using the depth marker located on the side of the ultrasound screen. Unless the patient is under general anesthesia or deeply sedated, use a 25-gauge needle to infiltrate the skin with a local anesthetic, such as 1 or 2% lidocaine.
Figure 3. Figure 3. Trajectory of the Introducer Needle.
Align the introducer needle with the center of the transducer. Approach the site at an angle of 30 to 45 degrees, with the long axis of the needle directed toward the sternal notch. Puncture the skin with the introducer needle at the center of the transducer, being careful not to damage the sterile sheath. When the needle passes underneath the transducer, the needle tip and the tenting of soft tissue can be viewed on the ultrasound screen. As soon as the tip of the needle appears as a dot on the screen, be sure to keep the needle tip under direct ultrasound visualization. The location of the needle tip may also be visualized by tilting the transducer back and forth or by withdrawing the needle and realigning it. If the needle contacts the clavicle, withdraw the needle and use a slightly deeper trajectory. As you advance the needle toward the vein, maintain negative pressure in the syringe until the vein is punctured (Figure 3).
To minimize the risk of a pneumothorax, always bear in mind the approximate depth of the subclavian vein and the extent to which the needle has been advanced. Check continuously for the aspiration of blood into the syringe. If blood is not aspirated as the needle is advanced, slowly withdraw the needle while maintaining negative pressure. Venous puncture may become evident as you withdraw the needle. As soon as blood is freely aspirated, set the transducer down, securely stabilize the needle, and disconnect the syringe. Confirm that the blood flow is nonpulsatile. Bright red, pulsatile blood suggests arterial puncture. However, dark, nonpulsatile blood does not rule out arterial puncture. A commercially available pressure-monitoring device or blood-gas analysis can also be used to confirm venous rather than arterial puncture.
Introduce a flexible guidewire through the needle and into the vein to a depth of 15 to 20 cm, depending on the size of the patient. While holding the guidewire in place, remove the needle. Now use ultrasonography to visualize the guidewire in the lumen of the vein on the screen in both the cross-sectional and longitudinal view. If there is any doubt about the location of the wire, confirm its location by advancing a small-gauge catheter over the wire, removing the wire, and connecting the catheter to a manometer or pressure transducer. Once you have ruled out the possibility of arterial cannulation, reinsert the guidewire through the catheter and then remove the catheter while leaving the guidewire in place.
Using a scalpel with a number 11 blade, make a small superficial incision at the entry point of the wire to facilitate passage of the dilator through the skin. Pass the dilator over the guidewire, being certain to maintain control of the wire at all times. Hold the dilator close to its tip and insert it under the skin, making sure that you do not create a kink in the guidewire. Generally, the dilator needs to be inserted only a few centimeters. Remove the dilator and anticipate increased bleeding at the puncture site. Maintain a grasp on the wire. A 4-by-4-inch gauze pad can be applied to the insertion site to minimize blood loss. Once again, only the wire remains in place.
Next, feed the catheter over the guidewire, being certain to maintain control of the external end of the wire before advancing the catheter through the skin. You will probably have to pull the wire out of the skin just slightly, until the external end of the wire extends beyond the catheter hub and can be grasped. While grasping the external end of the wire, advance the catheter over the wire. If you meet resistance, the tract may not have been adequately dilated. If this issue occurs, remove the catheter and reinsert the dilator. Insert the catheter to a depth that places the tip at the junction of the superior vena cava and the right atrium. Remove the guidewire and make sure that blood can be aspirated easily from all ports.
Figure 4. Figure 4. Catheter in Place with Sterile Dressing.
Flush all ports with sterile saline or heparinized saline solution. Place caps on the hubs, and secure the catheter. Apply a sterile dressing before removing the drape, or cover the area with a sterile 4-by-4-inch gauze pad, remove the drape, and then apply the sterile dressing (Figure 4). Obtain a chest radiograph to ensure that the catheter has been properly placed and that no hemothorax or pneumothorax has occurred. Dispose of all sharps in approved containers.