Vascular access is a requirement for most branches of medicine. The commonest need is for venepuncture; blood is routinely taken from the veins crossing the cubital fossa, alternatively from veins over the dorsum of the hand or the cephalic vein at the wrist. Larger volumes, and in cases of difficult access, the femoral and internal jugular veins may be used. The same veins may be used for administration of drugs and fluid, e.g. for anesthetic agents, and delivery of perioperative blood, and fluid support and replacement. Repeated access, e.g. for delivering chemotherapy and for hemodialysis, usually requires some permanent arrangement.
A common example is the Hickman line introduced using ultrasonic guidance into the subclavian vein, or surgically into the subclavian vein through the terminal cephalic vein, or alternatively, access via the internal jugular. Another method is to produce an arterialised vein by means of a surgically fashioned arteriovenous fistula, preferably in the non-dominant forearm. Arteries may be stabbed, e.g. for blood gas analysis and for monitoring arterial pressure. In all these situations, you need to know the normal anatomy of common access sites and possible complications of the proposed procedure.
For a venepuncture you will need a sterile syringe (usually 10 ml) and needle, a spirit swab to clean the skin just before skin puncture, a bottle to receive withdrawn blood, or a prepared giving set (set up in an aseptic fashion) capped with a two or three way tap, a pledget of cotton wool to press on the skin puncture site and a skin plaster, to cover this site when the bleeding has stopped. If the syringe nozzle is off center, keep this lowermost, and attach the needle with the bevel facing upwards. Tell the patient what you are going to do at each stage.
For venepuncture of an anticubital vein, examine both arms, and other sites if these veins are known to be inappropriate from previous
attempts or when preserving certain sites for dialysis. The median cubital vein joins the cephalic and basilic veins in front of the elbow and may have a median forearm tributary.
Once chosen, use some form of proximal compression to encourage venous filling. Gripping the upper arm by the patient or an assistant may suffice, but it is advisable to carry a quick release venous tourniquet or a length of rubber tubing for this application. It is applied tightly enough to compress the veins but not arteries. Once applied, it may be easier to feel rather than see a superficial vein in a fat arm. Clenching the fist four to eight times aids venous filling and gentle tapping over the vein also encourages dilatation. When access problems are anticipated, preheating the arm in warm water helps vasodilatation.
Once a dilated vein has been identified and its direction noted, choose a 1-2 cm segment and clean the skin over it with a spirit swab. Pick up the syringe and pierce the skin over the distal end of this segment, keeping the needle in line with the target segment (figure 100). The angle of venous entry and passing the needle along the vein is 10 – 20 degrees to the surface, but it may be easier to pierce the skin with an entry angle of 30 – 40 degrees, and then lower your hand once the subcutaneous level is reached. Watch the point of the needle pushing into and entering the superficial wall of the vein, and then advance it for 5 – 10 mm along the lumen.
Hold the syringe firmly in this position and use your other hand to withdraw the plunger. Once the required amount of blood has been obtained, use the withdrawing hand to release the tourniquet and place the pledget of cotton wool over the skin puncture site. Withdraw the needle and at the same time apply pressure over the puncture site. Ask the patient to take over this pressure and to bend their elbow, while you attend to the blood sample and ensure that the needle and syringe are appropriately disposed of. Maintain pressure for at least 2 minutes (longer if there is a history of oozing) and check that bleeding has stopped before applying the plaster.
If the needle is being used for infusion, release the tourniquet once it is in place and inject the prepared contents of the syringe, or hold the hub of the needle firmly, twist off the syringe and attach the giving set that you have prepared. Make sure the tubing is secured and the puncture site covered before attending to the infusion. The complications of anticubital puncture include stabbing a nerve (painful but not usually a long term problem) and entering the brachial artery; this passes along the medial aspect of the cubital fossa. Puncture is not usually a serious problem if recognized, but firm pressure must be applied on needle withdrawal. However, if the problem is not recognized, intra-arterial injection of certain compounds can be harmful, so carefully note the depth of your needle, the ease of withdrawal, the colour of the blood aspirated into the syringe and any associated pulsation of the blood column or the needle. If in doubt, apply pressure and start again later or at another site.
Bruising is a common complication and due to trauma to the vein wall, lack of adequate post-withdrawal pressure and any bleeding tendency. Make sure you can withdraw blood through the needle before injection, as extravasation of injected/infused material is painful and may harm subcutaneous tissues. For the same reason, ensure stability of any infusion line, and note the ease of the infusion and monitor all subsequent changes. Blockage of peripheral lines is common and it is essential, if you need to flush the system, to establish that the needle has not come out of the target vein. A later complication is thrombosis of the vein; this is usually painful. All pain associated with a line must immediately be investigated, to establish why and to stop any harmful infusion. An aseptic technique is essential, as infection in a line may not only produce a local inflammatory response but also has the potential of systemic spread of an infection.
The above steps can equally be used for other sites in the upper limb, notably the cephalic vein as it passes over the anatomical snuff box at the wrist) figure 101) and the veins over the dorsum of the hand (figure 102a). For longer periods of infusion, a cannula is used (figure 102b). This is mounted on a central needle. Techniques follow the same principles described but the needle is withdrawn once the cannula is housed within the vein; the tourniquet is first released and the infusion set attached, using full aseptic precautions.
More proximally in the upper limb, the subclavian vein is used for access, either from above or below the clavicle. The subclavian artery (figure 103) can be palpated as it crosses the first rib, behind the junction of the middle and medial thirds of the clavicle; the vein passes anterior and inferior to this point. The skin entry is just above the middle of the clavicle and directed at the suprasternal notch (figure104a).
The inferior access point is below the middle of the clavicle, directed at the same target (figure 104b). Problems of bruising are more severe because pressure cannot be applied to the subclavian vein, and one is usually inserting larger catheters in these larger proximal veins. Unwanted entry into the subclavian artery or the innominate artery bifurcation are possible, and must be recognized before any infusion. Ensure that the needle is kept close to the clavicle, to avoid damage to the pleura or the apex of the lung.
The internal jugular vein has a consistent surface marking deep to the triangle formed by the clavicular and sternal heads of the sternomastoid muscle, and the upper border of the clavicle. This can be palpated when turning the chin to the opposite side (figure 105a).
The patient lies supine, with their feet slightly raised, to engorge the internal jugular system. The needle is passed caudally in the parasagittal plane, at an angle of 30 degrees to the skin; it enters the internal jugular vein or its junction with the subclavian vein (figure 105b). Problems of bruising and intra-arterial injection are again present. Venous access in the internal jugular and subclavian veins is facilitated by using ultrasonic guidance.
The internal jugular site defined is also appropriate for surgical access. Another common surgical approach is through the terminal cephalic vein, as it passes along the medial border of the deltoid, over the clavicular head or pectoralis major, before it passes under the clavicle. A Hickman line is commonly inserted through both the internal jugular and cephalic vein approaches.
In the lower limb, rapid access to a large vein is through the femoral. The femoral artery is palpated with one hand and, after skin preparation, the needle is introduced a centimeter medial to this point and pointed cranially, at an angle of 30 – 40 degrees to the surface (figure 106). If the upper limb is inappropriate for long-term access, the great saphenous vein at the ankle has a consistent site, as it ascends over the anterior surface of the medial malleolus of the lower tibia. It is first palpated, by rolling from side to side, and proximal compression is applied before access with a needle or a cannula (figure 107a,b).
Complications are again bruising, and local infection and thrombosis of the line; the approach restricts mobility. The saphenous nerve is closely applied to the vein and should be avoided.
Venepuncture and cannulation of great saphenous vein at
Intra-arterial injections are usually the concern of experienced clinicians, such as radiologists, cardiologists or anesthetists. Aseptic precautions and preparation are again essential. The main difference is the direction of needle access. This is usually at 30 – 45 degrees to the skin surface, puncturing both anterior and posterior walls of the artery in a single movement, to transfix and stabilize the vessel; the needle is slowly withdrawn, while applying suction, until the lumen is reached. On withdrawal of arterial blood, lower your hand and advance the needle or cannula along the lumen and apply suitable equipment.
The commonest radiological approach is through the femoral artery (figure 108). This is palpated over the midinguinal point, i.e. midway between the anterior superior iliac spine and the midline, just below the inguinal ligament; this lies above the groin crease. The brachial artery is a common approach for the cardiologist, either by direct stab or a small cut down.
With the extended arm, the brachial artery can be palpated against the lower humerus at the upper border of the cubital fossa, the median nerve crosses it above this level and lies on its medial side (figure 109). The radial artery is easily accessible but requires sound technique. It is palpated over the anterior lower radius, just before it passes underneath abductor pollicis longus, to enter the anatomical snuff box (figure 110). In all arterial punctures, a constant firm pressure must be applied for four to five minutes on withdrawal of the needle or cannula.