The ultimate step to step guide for intravenous cannulation.

Intravenous cannulation


Intravenous cannulation the most common procedure in healthcare as increasing numbers of patients are treated for acute and chronic illnesses. The intravenous cannula is not used without risk, so it is essential that the healthcare practitioner can justify why the patient requires cannulation. As well as being able to safety management and provide ongoing care for patients with the cannula device.

What is cannulation?

Cannulation is the technique in which a metal tube is inserted in the body cavity, duct, or vessel as for drainage of fluid and administration of medication with its significance. It is used for rapid medication in liquid form. Generally, it is managing the flow of medication with its rate of flow.

The process of permanent removal of a cannula is called decannulation, which is especially of a tracheostomy cannula when a physician determines it is no longer used.

Device and equipment’s for cannulation-



Cannula is a flexible hollow tube, retractable inner core that is when inserted into a vein, an artery, or other body cavities that used either to withdraw fluid or insert medication. It is normally coming with a trocar that attached with it which allows puncture of the body to get into the intended space. The trocar is the sharped pointed needle that is attached to it.

In a general way, a trocar needle thus extending with the effective needle in length by at least half the length of the original needle. It is also called intravenous (IV) cannula. It is mainly in the range from 14 to 24 gauge (G) in size with different colors as coded.

Parts of the cannula-





-Catheter hub and wings


-Injection port cap

-Luer connector

-Needle grip

-Flashback chamber

-Luer lock plug

You may like- The ultimate guide for injection technique.

Cannula selection by indication-

ColorSizeUses  Flow rate
Orange14GFor rapid transfusion of whole blood  330 ml/min.
Gray16GFor rapid transfusion of whole blood or blood components215-220 ml/min.
Green18GFor surgical and other patients receiving blood components and large fluid volumes94-105 ml/min.
Pink20GFor receiving up to 2-3 liters per day, or long-term medication55-64 ml/min.
Blue22GFor long term medication, oncology patients, pediatric patients, adults with small veins. Suitable for IV contrast injection < 3ml/sec36 ml/min.
Yellow24GFor pediatric patients, neonates, elderly patients with particularly fragile veins24 ml/min.

Equipment’s for intravenous cannulation –


-Dressing/IV trolley with a sharps container and waste bag

-Dressing pack

-Nonsterile gloves

-Alcoholic chlorhexidine gauge

-Transparent semi-permeable dressing

-A cannula (size as per requirement)

-Giving and Extension set (and prescribed IV fluids)

-A waterproof protective cover or transparent cover

-Syringe 10ml with 0.9% Normal saline


-Fluid balance sheet

Preparing equipment for intravenous cannulation-

-Collect all the required equipment’s on the trolley near the patient with sharps containers.

-Intravenous fluids should be prepared by priming the giving set.

-The equipment should not be opened until in the patient room and patient education, assessment of vein and appropriate positioning have been attended.

Hand hygiene Process for intravenous cannulation-

How to hand rub  How to handwash
Apply a palmful of the product in a cupped hand and cover all surface.Wet your hands with water and apply enough soap to cover all hand surfaces.
Rub hands palm to palm.  
Put right palm over left dorsum with interlaced finger, and vice versa.  
Put palm to palm with fingers interlaced.  
Then, back of fingers into opposing palms with fingers interlock.  
Do rotational rubbing of left thumb, and vice versa.  
In rotational rubbing on forward and backward with clasped fingers of right hand in left palm, and vice versa.
After 20-30 sec. once dry, your hand is safe.  Rinse your hands with water.
 Dry thoroughly with a single-use towel.  
 Use a towel to turn off the tap.  
 After 40-60 sec. once dry, your hands are safe.

Hand hygiene is the most effective method for reducing the risk of infection during cannulation. The five steps moments for hand hygiene are-

-Before patient contact

-Before a procedure

– After the cannulation procedure or body fluid exposure risk

-After patient contact

-After contact with the patient environment.

Assessing and preparing the patient-

-Firstly, check the patient for baseline vital signs, diagnosis, and allergies to medications, cleansing fluids & dressings.

-Then provide a clear explanation of the procedure including potential adverse and side effects to the patient.

-Relaxed the patient because a relaxed patient is generally easier to cannulate.

-Assess the dominant/non-dominant side and check the veins for the status and suitability of the patient.

Positioning the patient for intravenous cannulation-

-If possible, use the non-dominant arm of the patient.

-Raise bed prior to further procedure.

-Place the arm in a supported comfortable position.

-Use a tourniquet to find a vein but release it when you are getting equipment ready.

-Position patient with pillows or towels for a relaxed position.

-Have an IV trolley close to you with the required equipment.

Process for preparing veins for intravenous cannulation-

For warm veins, you should-


-Washing patient hands under warm water

-Apply the warmed towel to the hand

-If the limb is warm ask the patient to gently clench and unclench their hand

– Gently rub up and down the vein.

Site for cannulation-

To initiate inteavenous cannulation effectively, the health care professional must have a clinical understanding of the anatomy and physiology of the vein, and surrounding structures of it.

Site for intravenous cannulation-

To initiate IV cannulation effectively, the health care professional must have a clinical understanding of the anatomy and physiology of the vein, and surrounding structures of it.

The Veins


The veins are a collecting system of vessels for blood returning from the peripheries to the heart, which is under low pressure. All veins except the pulmonary veins carry the deoxygenated blood and carbon dioxide.

-Veins are more superficial than arteries.

-These have valves and do not pulsate.

-These have less fibrous tissue than arteries, making them bouncy and easily compressible.

The superficial or cutaneous veins are generally used for peripheral IV access. They are made up of three layers –

Tunica intima is the innermost layer of the vein. It is composed of smooth endothelial cells and sub-endothelial connective tissue. The smooth surface promotes blood flow by preventing blood cells from adhering to the wall of the vessel. It is sensitive to changes in pH.

Damage to this lining or presence of foreign material induces an inflammatory response resulting in potential complications i.e. phlebitis, thrombus formation.


Tunica media is the middle layer of the vein. These are composed of elastic tissue and smooth muscle, where fibers more prone to collapse. It contains nerve fibers (vasoconstrictors and vasodilators) that can stimulate the vein to constrict or dilate.

vasoconstriction can occur in response to a sudden change in temperature e.g. if infusing cold fluids, or by mechanical or chemical irritation. stimulation of this layer can cause vasospasm. vein media thinner than artery media. Patients may feel pain during vein puncture when the needle penetrates this layer.

Tunica adventitia or externa is the outer layer of the vein. It is composed of connective tissue, collagen, and nerve fibers. It surrounds, supports, and protects the vessel. The blood vessels to the vein are also present in this layer. A hematoma may be formed if one of the vessels is penetrated.

Types of veins-

Metacarpal Veins

Veins that should be considered for peripheral cannulation are those found on the dorsal and ventral surfaces of the upper extremities, including the metacarpal, cephalic, and basilic, and median veins. Care must be taken to find a vein that is straight and will accept the entire length of the cannula. The back of the hand may be used but cannulation in this region will have a limited life span and can be more uncomfortable.


Dorsal digital veins– These are found along with the distal and lateral portions of the fingers and thumb. These are small and fragile.

As clinical propose, these are last resort cannula sites, due to the risk of mechanical phlebitis and infiltration. These are for short term use only and must be immobilized by utilizing a finger splint.

Dorsal metacarpal veins- These are found in between the metacarpal bones on the back of the hand. These are formed by the union of the distal veins.

As clinical propose, these are good sites for iv therapy but insertion can be painful because of nerve ending. It can accommodate 20-24G cannula and the tip of the cannula should not extend over the wrist joint.

Dorsal venous network- These are formed by the union of metacarpal veins, on the dorsal aspect of the forearm. It is not always prominent.

As a clinical purpose, these are comfortable for the patient and can accommodate 20-24G cannula.

Veins of the forearm-


Cephalic veins- These are lies along the lateral side of the forearm and runs along the radius. These run the entire length of the arm from wrist to shoulder and larger in size, so easy to access.

As clinical propose, these are excellent choices for cannulation and accommodates 16-24G cannula. These can be visualized above the acf. These are acceptable sizes for infusing chemically irritating solutions and blood products. These are should not be used for patients that require arteriovenous fistula formation.

Accessory cephalic veins– These are found on the top of the forearm and medium to large in size. These are branches of the cephalic vein.

As a clinical purpose, these are easily stabilized and accommodates 18-24G cannula. These are avoiding cannula tip placement at joint articulation.

Basilic vein– These are lies along with the medial (little finger) aspect of the upper forearm. These run the entire length of the arm from the wrist to the axilla. These are usually large and easy to visualize.

As clinical propose, these can accommodate 16-24G cannula. These often overlooked as vein rotates around the arm and is difficult to immobilize. The success can be achieved by placing the patient’s arm across their chest and approaching from the opposite side of the bad or by laying the arm along the side of the body and rotating inwards 90˚.

Median antebrachial vein– These arise from the palm of the hand, flow upward in the Centre of the underside of the forearm. These are medium in size and easy to visualize.

As a clinical purpose, these accommodate 20-24G cannula and may be difficult to palpate. These tendons run in parallel and not used as a first choice because it can be painful due to close proximity to the nerve.

Median cubital vein- These are lies in antecubital fossa (acf) and large vein easily visualized and accessed.

As a clinical purpose, these are usually used to draw blood and veins of choice for trauma or shocked patients as they can accommodate 14-24G cannula. The limits use for short peripheral cannula due to joint articulation, limits to patient mobility, and difficulty detecting infiltration. Complications at this site make use of veins distally contraindicated due to the risk of extravasation.

Veins of the antecubital fossa-

Veins in this area are short term use for short cannulation due to joint articulation, limit to patient mobility, and predisposition to mechanical phlebitis and infiltration.


Cephalic vein– A continuation of the vein upward from the anterolateral aspect of the forearm onto the anterolateral aspect of the arm over the biceps muscle. From here it passes through the deltoid muscle where, at a alternate variable point, when it passes through the superficial fascia to join the brachial vein that form the axillary vein.

Median cubital vein- There may be more than one ‘median’ vein in the antecubital fossa. They are formed by the convergence and divergence of branches of the three forearm veins.

Basilic vein– A continuation of the vein from the anteromedial aspect of the forearm. These may perforate the superficial fascia in the antecubital fossa and join the deep veins to form the brachial vein and may traverse the antecubital fossa and perforate the fascia at a variable point at the medial aspect of the arm.

You may like- The ultimate guide for blood pressure.

Vein selection for intravenous cannulation-

The main area of choice is between the wrist and antecubital fossa (acf) using the Cephalic, Median cubital, and Basilic veins. The upper arm should be avoided where possible as it reduces the ability to use veins in the lower arm later if extravasation or phlebitis occurs. The main superficial veins of the arm used in cannulation are-

-Digital veins

 -Metacarpal veins

-Dorsal venous arch vein

-Cephalic vein

-Basilic vein

-Antebrachial vein

-Antecubital veins

Do not use veins of the lower extremities unless absolutely necessary due to the risk of tissue damage, thrombophlebitis, and ulceration.

Sites to avoid in intravenous cannulation-

-Wrist, legs, feet or ankles

-Veins below a previous IV infiltration

-Vein below a phlebitic area

-Sclerosed or thrombosed veins

-Areas of skin inflammation

-An arm affected by a fundamental mastectomy, edema, blood clot, or infection also.

-An arm with an arteriovenous shunt of fistula.

Procedure for intravenous cannulation-

Choose the size of the cannula- The gauge needle is used as per the requirement, the higher the maximum flow rate of the fluid entering into the vein. Larger sized needles actually have a smaller number, so a 14G is large, while a 22G is small.

Select a proper size cannula that can easily fulfill the purpose of the procedure but is not oversized. The smallest needles are used in pediatrics and the largest is used for rapid transfusion.

Have a discussion with your patient- Firstly, informed the patient before you begin the procedure. This is basically done verbally that builds up a good connection with the patient and which allows for a less painful experience. Steps like-

-Introduce yourself to the patient.

-Verify the identity of the patient before starting the procedure.

-Explain the procedure to the patient and answer all the questions related to the procedure.

-Also, collect the history of any allergy or sensitivity that the patient may have about latex or gloves.

Wash your hands and put the gloves- It is essential and should follow through and proper hygiene practices before coming into contact with a patient. This is important to keep less the risk of infection from patient to a minimum when inserting the cannula by gently washing your hands thoroughly and putting the proper gloves.

This is important to keep less the risk of the patient getting infection to a minimum while inserting a cannula by washing your hands thoroughly and putting on gloves.

Use proper protective equipment for cannulation- Using gloves will not just protect your patient but it will also protect you from exposure to any bodily fluids and potentially infectious material. The single pair of non-sterile gloves will probably enough for protection. This is depending on your requirements, that you may also wear protective eye-wear when inserting or removing a cannula.

Apply the tourniquet around the patient arm- In most of the cases, the patient’s non-dominant arm is perfect. The tourniquet should be installed on the arm just above the site of cannulation. Tighten the tourniquet properly, so that the patient veins are highlighted. The other methods that are locating for a good vein are-

-Firstly, tapping on the vein to make it dilate.

-Ask your patient to open and close their fist.

-By using stress to highlight the vein by holding the patient arm down.

-Apply gentle heat at the site of the vein.

-If you getting difficulty in finding a good vein on the arm you have selected, then inspect the opposite arm. In any case, if the patient has diabetes or IV drug abuse history, then it may need to use an ultrasound to help you locate a good vein.

Clean the skin with a cleansing wipe- By an alcohol wipe or antiseptic solution, clear away pathogens present on the skin around the vein used for cannulation. Apply the solution at the site with friction for 30 to 60 seconds, and then allow the site to air dry for up to one minute.

It will help to prevent the risk of infection and reduce stinging at the site. If the site area is covered with hair, then you may need to clean it. It will help you to identify the vein and get a clear aim at it.

Insert the cannula at the appropriate angle- The perfect angle depends on the size of the cannula and the depth of the vein. If you trying to access a small, superficial vein, you should use a small cannula with a gauge of 22-24G and insert it at an angle of 10°-25°.

For a deep vein, you should use a larger cannula and insert it at an angle of 30°-45°. Make sure when you insert the needle then it bends up with its eye facing had upward. That means that the point of the needle is down against the skin.

Push the cannula slowly until you achieve flashback- Hold the cannula from the front of its wings with your pointer or middle finger and in the back with your thumb. Push it slowly into the skin until blood enters on the base of the cannula and this is called a flashback. It signals that you have entered into the vein.

Once you got a flashback, then reduce the angle of the needle to avoid puncturing the posterior wall of the vein.

Push the plastic piece slowly of the cannula- Now the needle should be held stationary and the plastic component of the cannula is advanced another 2-3 mm into the vein. To fit the plastic sheath into the vein and keep it there, when the needle is removed.

Keep pushing slowly the plastic component of the cannula until the plastic tube is fully inserted. The “hub” of the plastic component will hit on the skin when it on his way in.

Permit the blood to flow into the attachment- Remove the tourniquet from the patient arm and also the needle from the base of the cannula, leaving the plastic component insight. Allow blood to flow into the base of the cannula, so there is less risk of air entering into the vein if something is injected through the cannula, that called an air embolism. Then cap the cannula or attach other test tubes and other supplies to it.

Find another vein, if your cannulation is unsuccessful- If you are unable to cannulate a vein successfully, then never attempt to reinsert the needle. This could result in fragmentation of the cannula and embolism in the veins.

Secure the cannula with an appropriate gauge dressing- If the cannula reaches the site in the vein, you will need to secure it. By using transparent dressing and tape, or a specialized gauge that comes with the cannula, to secure the venous access device to the skin. Attach the cannula with the gauge inside the skin so that it is comfortable for the patient but stays it in the vein.

-If you are simply using the cannula to get samples of blood, then extensive securing is not required. However, if you need to be sure that it stays in place for long time use, so you may want to tape it down a bit.

Inspect and clean the cannula- First, pull back on the syringe to withdraw a little blood. It will confirm that the cannula is still at the site inside the vein. Then flush the cannula with a flushing normal saline or heparin solution. It will assure that the site is clean and will check for adequate positioning within the vein.

-To flush the cannula, it will need 5-10ml of saline in a syringe that may come in a pre-filled syringe or may need to fill it yourself.

Then flush the cannula by attaching the saline syringe into the cannula port, inject the saline into the port, detach the syringe, and then close the cap.

-If you are again using the cannula for injection, flush it with saline solution again. It will assure that the cannula is still in at the site in the vein.

Re-cannulation, if required- If you do not observe blood in the flashback chamber when you inspect the cannula, you will need to re-cannulation the vein. If there is no flashback, this means that maybe the cannula has punctured the posterior wall of the vein. It can also occur in patients who severely have low blood pressure. Withdraw the device until it is just below skin level, and attempt to re-cannulate.

-If swelling forms at the site, then remove the device and release the tourniquet. Apply direct pressure at the site for five minutes.

Clean up after the procedure-

Dispose of the needle to reduce the risk of a needle stick and other waste properly in a sharp’s container.

-Document the procedure in the proper set of notes.

When removing the cannula, place a piece of gauze on the injection site and keep the gauge or a bandage at the place. It will assure that the patient is not bleeding after the procedure.

Complications in intravenous cannulation-

Complications with IV cannulation are very common. They are divided into two categories-

-Complications related to the insertion of the line

-Complications related to the fluids administered.

Infection is the most common serious complication related to the insertion of the cannula. Other complications related to it are-

-Infiltration- Damage to the vein and leaking of blood into nearby tissues.

-Hematoma- Bruising at the insertion site.

-Phlebitis- Mechanical irritation or inflammation of the veins.

-Thrombosis- formation of blood clots at the tip of the cannula.

-Extravasation- Accidental puncture of an artery during insertion.

-Air embolism- Air in the cannula.

-Catheter blockage.

-Accidental dislodgement of the cannula.

Complications allied with medications and fluids administered by intravenous cannulation are-

-Medication irritating the vein

-Allergic reactions to medications

-Irregular heartbeat resulting from the too rapid infusion of fluids

Leave a Reply