Intravenous Cannulation

Intravenous (IV) cannulation is a technique in which a cannula is placed inside a vein to provide venous access. Venous access allows sampling of blood, as well as administration of fluids, medications, parenteral nutrition, chemotherapy, and blood products.[1]

Veins have a three-layered wall composed of an internal endothelium surrounded by a thin layer of muscle fibers that is surrounded by a layer of connective tissue. Venous valves encourage unidirectional flow of blood and prevent pooling of blood in the dependent portions of the extremities; they also can impede the passage of a catheter through and into a vein. Venous valves are more numerous just distal to the points where tributaries join larger veins and in the lower extremities.[2]

This topic describes placement of an over-the-needle IV catheter, in which the catheter is mounted on the needle (see the first image below). Such devices are available in various gauges (16-24 gauge), lengths (25-44 mm), compositions, and designs (see the second image below).

In general, it is advisable to select the smallest gauge of catheter that can still be effectively used to deliver the prescribed therapy; this will minimize the risk of damage to the vessel intima and ensure adequate blood flow around the catheter, which reduces the risk of phlebitis.[3]  However, if the situation is an emergency or if the patient is expected to require large volumes infused over a short period of time, the largest-gauge and shortest catheter that is likely to fit the chosen vein should be used.

Veins with high internal pressure become engorged and are easier to access. The use of venous tourniquets, dependent positioning, “pumping” via muscle contraction, and the local application of heat or nitroglycerin ointment can contribute to venous engorgement.[2]

The superficial veins of the upper extremities are preferred to those of the lower extremities for peripheral venous access because cannulation of upper-extremity veins interferes less with patient mobility and poses a lower risk for phlebitis.[4]  It is easier to insert a venous catheter where two tributaries merge into a Y-shaped form. It is recommended to choose a straight portion of a vein to minimize the chance of hitting valves.

This article describes the placement of an IV catheter in an upper extremity. A similar technique can be used for placement of IV catheters in different anatomic sites.

Indications for IV cannulation include the following:

• Repeated blood sampling
• IV administration of fluid 
• IV administration of medications 
• IV administration of chemotherapeutic agents 
• IV nutritional support
• IV administration of blood or blood products 
• IV administration of radiologic contrast agents for computed tomography (CT), magnetic resonance imaging (MRI), or nuclear imaging

No absolute contraindications for IV cannulation exist.

Peripheral venous access in an injured, infected, or burned extremity should be avoided if possible.

Some vesicant and irritant solutions (pH < 5, pH >9, or osmolarity >600 mOsm/L) can cause blistering and tissue necrosis if they leak into the tissue, including sclerosing solutions, some chemotherapeutic agents, and vasopressors. These solutions are more safely infused into a central vein. They should only be given through a peripheral vein in emergency situations or when a central venous access is not readily available.

Equipment used for intravenous (IV) cannulation includes the following (see the images below):

• Nonsterile gloves
• Tourniquet
• Antiseptic solution (2% chlorhexidine in 70% isopropyl alcohol)
• Local anesthetic solution
• 1-mL syringe with a 30-gauge needle
• 2 × 2 in. gauze
• Venous access device
• Vacuum collection tubes and adaptor
• Saline or heparin lock
• Saline or heparin solution
• Transparent dressing
• Paper tape

Anesthesia

Both intradermal injection of a topical anesthetic agent just prior to IV insertion[5]  and topical application of a local anesthetic cream[6]  about 30 minutes prior to IV insertion have been shown to achieve significant reduction of the pain associated with the procedure. Both should be used unless the situation is an emergency.[7]

Positioning

Make sure that there is adequate light and that the room is warm enough to encourage vasodilation. Adjust the height or position of the bed or chair to make sure you are comfortable and to prevent unnecessary bending. Make sure the patient is in a comfortable position, and place a pillow or a rolled towel under the patient’s extended arm.

The patient’s skin should be washed with soap and water if it is visibly dirty.

Use properly fitted nonsterile gloves and eye protection device to prevent exposure via accidental blood splashes.

The technique of intravenous (IV) cannulation is outlined in the following section, as well as in the video below.

Place a venous tourniquet over the patient’s nondominant arm, and select a site for IV catheter insertion. The veins of choice for catheterization include the cephalic or basilic veins, followed by the dorsal hand venous network (see the images below).[8]

For prolonged courses of therapy, it is recommended, though not always practical, to start distally and move proximally as distal catheters are replaced.

If difficulty is encountered in finding an appropriate vein, one of the following techniques may be used:

• Inspection of the opposite extremity
• Opening and closing the fist
• Using gravity (holding the arm down)
• Gentle tapping or stroking of the site
• Applying heat (warm towel/pack) or a nitroglycerin ointment

Application of a tourniquet to the proximal arm with infusion of 60 mL of normal saline solution via a small IV catheter that is inserted distally may cause enough venous engorgement to allow placement of a more proximal large-bore IV catheter.[9]

Ultrasound guidance has been shown to facilitate peripheral venous placement in emergency department (ED) patients with difficult IV access and should be used when appropriate veins are not readily visualized or palpable.[10]  Risk factors for difficult venous access in the ED include diabetes, sickle cell disease, and a history of IV drug abuse.[11]

The author recommends the use of ultrasound guidance in patients who have difficult venous access or those in whom venous cannulation by standard methods has failed.[12]  Ultrasound-guided peripheral IV access has been associated with reductions in central venous catheter placement, particularly in noncritically ill patients.[13]

Transillumination is another technique that can be used in patients with difficult IV access.[14]

Apply an antiseptic solution (eg, 2% chlorhexidine solution or 70% alcohol) with friction for 30-60 seconds (see the image below). Allow to air-dry for up to 1 minute to ensure disinfection of the site and to prevent stinging as the needle pierces the skin. Once the skin is cleaned, do not touch or repalpate it.

While the skin is allowed to dry, flush the saline or heparin lock with the appropriate solution. The syringe may be left attached to the tubing (see the image below).

Unless the situation is an emergency, if the patient is interested in local anesthesia, infiltrate 0.5-1 mL of a local anesthetic using a 25- or 30-gauge needle to raise a wheal at the site of catheter insertion (see the image below).

Stabilize the vein using your nondominant hand (thumb) to apply traction to the skin distal to the chosen site of insertion (see the image below). This will prevent superficial veins from rolling away from the needle. Stabilization should be maintained throughout the procedure.

Hold the venous access device in your dominant hand with the bevel facing upward; this will ensure smoother catheterization because the sharpest part of the needle will penetrate the skin first. Release the needle from the catheter and replace it, confirming that the catheter was not damaged or fragmented. This will ensure smooth advancement once the venous access device is inside the vein.

The angle of the needle entry into the skin will vary according to the device used and the depth of the vein (see the image below). Small superficial veins are best accessed by using a small catheter (22-24 gauge) placed at a 10-25º angle. Deeper veins should be accessed with a larger catheter at a 30-45º angle.

Upon entry into the vein, the practitioner might feel a “giving way” sensation. Blood should appears in the chamber of the venous access device (ie, flashback). (See the image below.) The angle of the venous access device should be reduced to prevent puncturing the posterior wall of the vein. It should be advanced gently and smoothly an additional 2-3 mm into the vein.

If no blood is observed in the flashback chamber, the device should be withdrawn to just beneath the skin level, and another attempt to recatheterize the vein should take place. Flashback may stop if the device has punctured the posterior wall of the vein or if the patient is extremely hypotensive. If swelling develops, withdraw the device, release the tourniquet, and apply direct pressure for 5 minutes for a hematoma.

If venous catheterization is unsuccessful, the needle should never be reintroduced into the catheter. This could result in catheter fragmentation and embolism.

After the venous access device’s hub is dropped to the skin, maintain skin traction with your nondominant hand. Hold the needle grip of the venous access device in place between your dominant thumb and middle finger, while using your dominant index finger to slide the hub of the catheter over the needle and into the vein (see the image below).

Use your nondominant middle finger to apply pressure over the catheter to prevent blood spill, and hold the hub in place using your nondominant index and thumb fingers. Then use your dominant hand to withdraw the needle (see the image below). Secure the needle in its safety cover, a dedicated biohazard sharps container, or both.

If blood sampling is needed, attach an adapter or a syringe to the hub and obtain the required samples (see the image below).

Release the tourniquet. While applying pressure to the catheter to prevent blood spillage and while continuously stabilizing the hub and wings to the skin as previously described, disconnect the blood sampling adapter or syringe, and securely attach the preflushed saline or heparin lock to the hub of the venous access device. Secure the venous access device to the skin using the transparent dressing and tape (see the image below).

Using the saline or heparin flush syringe, withdraw a small amount of blood to verify that the catheter is still inside the vein. Immediately flush the tubing with the remainder of the solution. Slide the plastic tubing lock, and continue to lock the tubing (if such a lock is available). (See the image below.)

Finish securing the tubing to the skin using tape. Place a label indicating the date, the time, and other facility-specific required information over the transparent dressing (see the image below).

Removal of peripheral IV catheters can be performed as clinically indicated; the catheters should not be routinely replaced on a fixed schedule.[15, 16]

Stop infusion solution and disconnect the tubing, leaving just the saline/heparin lock tubing connected to the venous access device. Release the adhesive tape and transparent dressing from the skin. Withdraw the catheter outside of the vein (see the image below), and apply direct pressure with gauze to the catheter insertion site for at least 5 minutes.

Inspect the catheter for fragmentation. Document in the patient’s chart the date, time, and reason for catheter removal and the integrity of the catheter as inspected. Place a 2 × 2 in. gauze pad or a cotton ball with a paper tape over the IV insertion site. Instruct the patient to continue manual pressure for 10 more minutes in order to minimize hematoma formation.

Periprocedural and postprocedural complications may include the following:

• Pain
• Failure to access the vein
• Blood stops flowing into the flashback chamber
• Difficulty advancing the catheter over the needle and into the vein
• Difficulty flushing after the catheter was placed in a vein
• Arterial puncture
• Thrombophlebitis
• Peripheral nerve palsy
• Compartment syndrome
• Skin and soft tissue necrosis

For pain, application of an anesthetic cream 30 minutes beforehand, subcutaneous infiltration of an anesthetic solution, or both should be used prior to peripheral IV insertion whenever possible.

Collapse of the vein, inadequate skin traction, incorrect positioning, and incorrect angle of penetration can all lead to a failed attempt at accessing the vein. In this case, either attempt insertion at a different site or, if it is believed that the selected vein should be accessible, withdraw the venous access device to just beneath the skin and reattempt insertion.

If blood stops flowing into the flashback chamber, the cause might be vein collapse, venospasm, needle hub position against a venous valve, or penetration of the posterior wall of the vein. Observation of a developing hematoma necessitates removal of the catheter. In this case, release and then reapply the venous tourniquet, and attempt to gently stroke the vein to engorge it with blood and release venospasm. Finally, attempt to withdraw the needle a few millimeters to move it away from a valve.

Failure to release the catheter from the needle before insertion, encountering a venous valve, removing the needle too far with the catheter being too soft to advance into the vein, poor skin traction, or venous collapse can all lead to difficulty in advancing the catheter over the needle and into the vein. In this case, release the tourniquet and then reapply it to help engorge the vein. Connect a syringe with normal saline (0.9%) solution to the hub, then attempt to “float” the device in place by simultaneously flushing the catheter and advancing it.

Difficulty flushing after the catheter was placed in a vein can be caused by the catheter tip position against a venous wall or a valve, blood clot, or piercing of the venous wall. Observation of a hematoma necessitates removal of the catheter. In this case, withdraw the catheter slightly to release it from a wall/valve and attempt to flush it back in.

In the case of arterial puncture, palpate the vein carefully before attempting to insert a venous access device to ensure that there is no palpable pulse in the vessel. If an accidental arterial puncture has occurred, as evidenced by arterial pulsation of blood out of the catheter, remove the catheter and apply direct pressure using gauze for at least 10 minutes.

Thrombophlebitis can be caused by thrombus formation with subsequent inflammation, infection, or both. Pain in the IV site along the path of the catheter, skin erythema or induration, swelling, drainage from the skin puncture site, or presence of a palpable venous cord are the signs of thrombophlebitis.

Remove the catheter and treat with appropriate antibiotics if you suspect an infectious etiology. Regularly and at least daily inspect the site of insertion for signs of infection. Some sources recommend that peripherally inserted IV catheters be routinely replaced every 3-4 days, whereas others suggest that with proper antiseptic technique and at least daily monitoring of the insertion sites, less frequent replacement may be safe, as long as no signs of phlebitis are present.[17, 16]

Accidental puncture of the median nerve is rare but possible, in that this nerve is located just posterior to the basilic vein in the antecubital fossa. Other peripheral nerves might be accidently punctured, causing pain and (rarely) paralysis when other veins are selected.

Continuous infusion of solutions into a venous access device that extravasated into the surrounding tissue might result in a compartment syndrome. Make sure to monitor the site while the transfusion is taking place, and use extra caution in patients who are unable to communicate pain or discomfort. Some infusion pumps are preset to stop the infusion and sound an audible alert with any increase in resistance to flow.

Some vesicant and irritant solutions may cause severe soft-tissue damage if they extravasate outside of the vein and into the surrounding tissue.