A guide to cannulation in adults

Intravenous cannulation is a widely practised invasive procedure globally, involving the insertion of a slender, flexible tube containing a retractable needle into a peripheral vein (Boyd, 2022). This technique serves as a gateway for various medical interventions, including the delivery of fluids, medications, dyes, contrast agents and blood products, as well as the collection of blood for diagnostic purposes (Helm et al, 2015). Nonetheless, conducting cannulation involves inherent risks. Hence, it becomes crucial for health professionals to ensure safe practice by recognising their own limitations, comprehending the theoretical foundations of the insertion procedure, and maintaining awareness of the associated risks in this clinical skill (Nursing and Midwifery Council (NMC), 2018; 2023).

When performing cannulation on individuals with compromised immune systems, it is of utmost importance to take additional precautions to reduce the risk of infection and safeguard their health. Immunocompromised individuals possess weakened immune defences, making them more susceptible to infections. As a result, there may be a need for extra precautions, which could involve maintaining rigorous aseptic non-contact methods and creating a sterile environment (UK Oncology Nursing Society (UKONS), 2023).

Aseptic non-touch technique

The aseptic non-touch technique (ANTT) is a method employed to minimise the likelihood of patients contracting infections during clinical procedures. It accomplishes this by safeguarding ‘Key-Parts’ and ‘Key-Sites’ from micro-organisms that might be transmitted from healthcare personnel or the nearby environment. Key-Sites are classified as parts of the body into which infection might be introduced during a procedure, for example, an opening in the skin, urethra or cannula insertion site; whereas Key-Parts are associated with the equipment that might come into contact with Key-Sites or other Key-Parts, such as dressings, catheters and syringe tips. These should not be touched or only touched with sterile gloves and sterile equipment.

There are two main variants of ANTT: standard, which is used for uncomplicated, simple and quick procedures involving few Key-Sites or Key-Parts, and surgical, for those skills and procedures that are more complex, lengthy and involve a large number of or multiple Key-Sites or Key-Parts.

When carrying out a clinical procedure, an ANTT risk assessment is required to ascertain if the procedure necessitates the adoption of a standard or surgical ANTT approach. This involves assessing the difficulty of protecting the Key-Parts and Key-Sites associated with the skill, while also considering the number and sizes of the Key-Parts, environment, invasiveness and user competency (Association for Safe Aseptic Practice (ASAP), 2015). For standard ANTT procedures, non-sterile gloves can be worn as the Key-Parts, and Key-Sites are limited, such as in cannulation and venepuncture. However, for surgical ANTT procedures such as urinary catheterisation and wound care, sterile gloves must be worn, due to the level of invasiveness (ASAP, 2015).

Informed consent, patient preparation and pain management

Where possible, informed consent should be obtained. This will include ensuring that the patient is aware of the reasons for the cannula, the associated risks and complications and details of the care of the device. Providing this level of information will not only ensure that the patient can provide valid consent, but it will also assist in building rapport and a trusting therapeutic relationship, which could help reduce any fears or anxieties. It is also important to consider not only the patient's comfort but also the potential to cause pain, thus appropriate multimodal approaches to pain assessment and management need to be undertaken in order to minimise the risks of harm. For cannulation, this can include the use of pharmacological and non-pharmacological approaches such as distraction therapy and topical analgesics (Ford, 2019).

Anatomy of the hand and forearm

Unlike when performing venepuncture, the antecubital fossa region should be avoided where possible. This is especially true when placing cannulas that will be sited for longer periods, as flexion of the arm may impede the ability of the cannula to function correctly and increase the possibility of the cannula becoming occluded. Rickard et al (2012) stated that occlusion is one of the most common reasons for cannula failure and may lead to the patient experiencing unnecessary discomfort if the cannula needs to be removed and resited. It is, therefore, best practice to use the cephalic or basilic veins on the forearm or the dorsal metacarpal veins on the back of the hand (see Figure 1) (Thomas, 2015).

Innovations in clinical practice

Due to advances in technology, there are some instances where additional equipment can be used to aid healthcare providers in locating and visualising veins during the process of inserting a cannula. This is particularly beneficial in situations where veins are difficult to locate or when dealing with patients who have challenging vascular access due to factors such as obesity, dehydration, or underlying medical conditions (Tada et al, 2022). Ultrasound-guided cannulation refers to the use of an ultrasound machine equipped with a high-frequency transducer that emits sound waves into the body and receives echoes to create real-time images of the underlying structures. However, although ultrasound-guided cannulation helps minimise complications such as infiltration and nerve injury and increases insertion success rates, it also requires additional training, can be costly, time-consuming and is not always readily available (Gottlieb et al, 2023).

As an alternative to ultrasound technology, there are light-based vein finders or vein illumination devices available. These are typically portable and handheld gadgets that emit near-infrared (NIR) or ultraviolet (UV) light onto the patient's skin. This special light interacts with the haemoglobin in the blood, causing veins to become more distinct and easier to visualise. This enhancement in contrast makes it simpler to distinguish veins from the surrounding tissue. Light-based vein finders have advantages over ultrasound machines in terms of ease of use and speed. They prove especially beneficial when dealing with infants and elderly patients when ultrasound procedures may be less convenient. However, it is important to note that these vein finders have limitations. They may not be effective for visualising deep veins or in cases where there are challenges related to the thickness of the surrounding tissues (Pan et al, 2019).

Choosing the correct site, vein and cannula size

The National Institute for Health and Care Excellence (NICE) (2017) recommends that, before insertion of a cannula, a clinical decision in relation to the site and choice of vein needs to be undertaken by the health professional performing this task, in order to reduce the risk of cannula failure and associated complications. The decision should take into consideration the patient's preferences, their level of acuity, vein accessibility, medical history and cannulation history. Sites and veins to avoid include those affected by the patient's clinical condition. For example, post-mastectomy, using the side associated with breast surgery is contraindicated due to the complications associated with potential lymphoedema development post-node removal (Thomas, 2015). Veins that are small, superficial, sclerosed, pulsate or close to arteries should also be avoided, in order to reduce the risks of complications developing during and after the insertion period (Rickard et al, 2012). Complications can also be avoided by using veins with a larger diameter, in the upper extremities and with good capillary refill (Lister et al, 2021). Factors that would affect the decision for the site and vein choice have been summarised in Box 1.

Box 1.Choosing a vein
Veins in upper extremities

Source: adapted from Rickard et al, 2012; Thomas, 2015; Lister et al, 2021

Moreover, in an attempt to improve vessel health, it is vital that health professionals possess knowledge and understanding of alternative vascular access devices, and use the Vessel Health and Preservation (VHP) framework, in order to assess whether a peripheral cannula is the most appropriate device to use (Hallam et al, 2016). If a peripheral cannula is the most suitable vascular access device, then it is important to choose the correct size (length and width) and type (ported or non-ported). Thomas (2015) advocates that health professionals should use the shortest and smallest gauge capable of achieving the required flow rates in order to meet the clinical need. Because there is a vast array of devices available, from several manufacturers, it is also important to take into consideration specific design features (such as wings and ports) when choosing which device to use.

Cannula insertion procedure

To carry out the procedure, additional equipment is required (see Box 2), all of which should be checked prior to carrying out the procedure. The procedure is as follows:

• Communicate with the patient and provide them with relevant information in order for them to provide informed consent. This will also provide you with the opportunity to talk about previous experiences with cannulation, ascertain if the patient has any allergies to dressings, assess for potential complications and physically prepare the patient and the environment prior to collecting the equipment.
• Decontaminate hands. With the patient's arm in a comfortable and appropriate position, apply the tourniquet 7-10 cm above the chosen site. To encourage venous filling and vein distention, ask the patient to open and close their fist, use gravity by asking the patient to hang their arm down, apply a warm compress, or lightly stroke the vein in a downward motion (Phillips and Gorski, 2014).
• With two fingers, palpate the vein in order to confirm suitability (see Figure 2a) and release the tourniquet.
• Decontaminate hands, clean the tray/receptacle and gather the equipment, ensuring that you check for damage and contamination. Place equipment into the clean receptacle using the ANTT (do not touch the Key-Parts - the tip of the cannula and the end of the syringe for flushing).
• Reapply the tourniquet; do not over tighten as this may obstruct arterial flow.
• Clean the chosen site with the alcohol-based (2% chlorhexidine in 70% isopropyl alcohol) preparation equipment (see Figure 2b). Ensure that you abide by the manufacturer's application instructions and allow the area to dry for 30 seconds. Do not touch the skin or re-palpate the vein after application of the skin preparation (Lister et al, 2021).
• While waiting for the skin preparation solution to dry, decontaminate hands and don gloves.
• Prepare the cannula device by removing the needle guard and assessing the tip for damage.
• Then with your non-dominant hand apply traction to the skin and stabilise the vein below the chosen site. Advise the patient that they will feel a sharp scratch.
• Insert the cannula at an angle of 20-30 degrees (depending on the manufacturer's instructions), ensuring that the bevel is up and observe for the first flashback of blood into the cannula (see Figure 2c).
• Lower the angle of insertion by dropping the cannula closer to the skin and advance the device slightly.
• Then continue to advance the cannula 2 mm and draw the stylet back 2-3 mm, noting the second flashback in the lumen of the cannula (see Figure 2d).
• Slide the cannula over the needle, advancing further into the vein. Keeping traction on the skin will make this process easier.
• Release the tourniquet, apply pressure beyond the cannula tip, loosen the cap at the end of the stylet and withdraw the needle, placing it immediately into the sharps waste container. In line with the Health and Safety Executive (HSE) (2013) regulations, the cannula will have a safety device (active or passive) in place to prevent a sharps injury. Depending on the specific design, it may also have a passive safety feature that prevents the reinsertion of the needle back into the lumen of the cannula, reducing the risk of cannula tip damage (see Figure 2e). Reapply the cap before releasing pressure and fix the cannula in place with a semi-permeable film dressing.
• Flush with 0.9% sodium chloride (not required if using an extension set, or an integrated cannula), and ensure patient comfort.
• Dispose of waste, remove gloves and decontaminate hands using the appropriate technique (Ford and Park, 2018; 2019).
• Document your care (via paper-based or electronic platforms) according to trust guidelines and protocols. This should include, as a minimum standard, your signature, date and designation, the time, cannula size, site of insertion, the number of insertion attempts, and any noted insertion complications. Further documentation such as the Visual Infusion Phlebitis (VIP) score may also need to be completed, depending upon trust requirements.

Box 2.Equipment required

• Non-sterile gloves
• Alcohol gel
• Procedural tray
• Disposable tourniquet
• Alcohol-based cleansing product
• Cannula
• Needle-free connector
• Extension set (if required)
• Saline flush
• Sterile film dressing
• Sterile gauze
• Sharps disposal bin
• Cannula care plan
• Pillow
• Sterile field or cannula pack

Source: Lister et al, 2021

Risks and hazards

Research by Wallis et al (2014) and Helm et al (2015) suggested that catheter-related failure complication rates vary between 35% and 50%. These can be avoided if health professionals adhere to sound infection control and prevention precautions, choose the right vessel, use correct insertion techniques, and have an awareness of the anatomy (Lister et al, 2021). Additionally, as with any clinical procedure, the appropriately trained person must be aware of the risks involved, not only for themselves but also to the patient and others.

Safety of the practitioner

One of the greatest dangers to health professionals when undertaking procedures using hollow-bore needles, is the risk of contracting a blood-borne infection via a sharps injury (HSE, 2013). Due to the frequency of undertaking cannulation, nurses are one of the health professional groups most at risk (Woode Owusu et al, 2015). Health professionals can be exposed to 30 potentially dangerous pathogens, including hepatitis B and C (European Biosafe Network, 2011). Therefore, in order to ensure safe practice, personal protective equipment, which is a universal precaution, must be worn (Ford and Park, 2019). Kinlin et al (2010) stated that the use of gloves has been shown to be beneficial in reducing the transmission of blood-borne infections by decreasing the inoculum of blood introduced during a sharps injury. Additionally, all devices used must adhere to sharp safety regulations, must be checked before use, used as instructed by the manufacturers and disposed of correctly (HSE, 2013).

Safety of the patient

The risks of inserting a foreign object into a patient's arm must be considered, especially in relation to the risk of complications such as infection, haematoma, arterial puncture, and nerve injury and the steps to be taken if they occur (Buowari, 2013).

The following list (which is not exhaustive) provides a brief overview of some of the complications associated with peripheral vascular cannulation during insertion and in the post-insertion period (Rickard et al, 2012; Royal College of Nursing, 2016; Lister et al, 2021).

Insertion complications

• Nerve injury: this can occur through poor vein choice and often results in shooting or burning pain, or sharp tingling. If this occurs, the needle and tourniquet must be removed
• Haematoma: infiltration of blood into the surrounding tissues is often caused by poor insertion technique, inappropriate vein selection, inadequate pressure upon removal, incorrect use of the tourniquet or of a cannula size that is too large for the chosen vein. The risk of this occurring is increased in a patient who is receiving anticoagulant therapy
• Arterial puncture: the inadvertent puncture of an artery rather than a vein can occur if there has been an inadequate assessment of the site and the vein chosen is very close to an artery. This can result in the formation of a haematoma and other symptoms such as numbness, pain, paleness and coldness of the limb or hand. If an arterial puncture occurs, remove the cannula, apply pressure and raise the patient's arm.

Post-insertion complications

• Phlebitis: this is defined as irritation or inflammation of the vein, caused by chemical, mechanical or biological means. Patients can display a range of symptoms, which can include localised pain, oedema and erythema. If this occurs and depending on the VIP score, the cannula may need to be removed and resited. To aid with the discomfort and swelling that can be experienced, a warm or cold compress can be applied
• Thrombus: in some cases, a thrombus may develop within the vein that has been used for cannulation. A thrombus can also occur secondary to phlebitis (thrombophlebitis), and it may be necessary to remove and resite as per the VIP protocol
• Infiltration: this relates to the administration of non-vesicant medication and fluids into the adjacent tissue rather than the vein (Phillips and Gorski, 2014). The severity of the complication is usually graded using an infiltration scale, and close monitoring of the patient, cannula site and surrounding tissue will be needed, to assess deterioration or improvement. The VIP score will also need to be recorded
• Extravasation: this complication is defined as the administration of vesicant intravenous fluids or medications into adjacent tissues rather than the vein, which subsequently leads to blistering and possible tissue necrosis (Phillips and Gorski, 2014). Immediate signs include a slowed infusion rate, pain, oedema, and skin blanching. If extravasation occurs, the infusion of fluid or medication must be stopped immediately and advice sought in relation to whether the fluid or medication needs to be aspirated. In some cases, the cannula will, therefore, need to remain in situ for aspiration and antidote administration to occur. As in the case of phlebitis, warm or cold compresses might be beneficial, and limb elevation may be required due to oedema
• Air embolism: this occurs when air or gas is admitted, iatrogenically, into the vascular or arterial system and, although rare, it can be fatal. In the case of cannulation, it can be avoided by the correct priming of the fluid administration set so that no air enters the bloodstream. Signs and symptoms include tachypnoea, reduced oxygen saturations, hypotension, tachycardia and chest pain.

Top tips

The following information has been collated by Northumbria University staff in relation to some of the common errors that students encounter when undertaking cannulation in clinical practice. Using simulation training aids can help build students' skills and confidence.

• Missed vein – ensure you use your fingers to anchor the vein, below the intended insertion point, as this will prevent the vein from moving and ensure easier entry. Also, spend time assessing the site and locating the most optimal vein. If you choose one of the largest veins, then the likelihood of missing the vein will be reduced
• For veins that are difficult to locate, use additional assistive technologies such as vein location tools and ultrasound, which can be used with assistance from a trained operator
• If blood is required for analysis, this must be taken prior to the administration of any medication. Please refer to the article by Skarparis and Ford (2018) for further details on the procedure for taking blood
• Consider whether a peripheral cannula is the best device for the delivery of fluids and medications. Use the VHP framework and continually re-evaluate vessel health.

Post-procedure care and education

After the peripheral cannulation procedure, post-procedure care and patient education emerge as crucial elements in ensuring the patient's wellbeing, safety, and the overall success of intravenous (IV) therapy. Continual assessment plays a pivotal role in post-procedure care, with health professionals maintaining regular evaluations of both the cannulation site and the patient's overall condition. Furthermore, it is imperative to educate the patient about the signs of complications and infection, such as redness, swelling, pain or discharge, and closely monitor them for any such indications.

To prevent dislodgement, contamination and infection, it is essential to secure the cannula effectively using an appropriate semipermeable film dressing. Depending on local protocols, health professionals may also implement cannula care plans to facilitate monitoring and assessment of the cannulation site, recording scores for potential issues such as infiltration and extravasation.

Providing reassurance to the patient can significantly enhance their comfort and minimise irritation at the cannulation site. Simple strategies, such as using pillows or cushions to support the arm and reduce pressure on the site, can prove beneficial. Additionally, patients should be advised not to interfere with or touch the cannula or dressing to maintain its integrity and minimise the risk of complications.

Conclusion

Cannulation is a clinical skill that requires health professionals to have a sound understanding of the underpinning principles, as well as a comprehensive awareness of the technique aligned with the clinical procedure. Therefore, although it is important to review local and national guidelines and associated literature, it is also vital to use every opportunity to practise this skill in clinical practice, in addition to using alternative education and learning strategies such as simulation training aids, in order to maintain contemporary practice (NMC, 2023).

KEY POINTS

• Intravenous cannulation is a widely practised invasive procedure which uses an aseptic non-touch technique (ANTT) and requires a sound understanding of anatomy and physiology
• This skill is associated with several risks for both health professionals carrying out the procedure and the individual who requires the intervention
• For students, the opportunity to practise this skill in clinical practice is sometimes difficult; therefore, alternative education and learning strategies such as simulation can prove extremely beneficial in acquiring and maintaining practice
• Peripheral cannulation may not always be the best option and therefore health professionals may need to consider other alternatives by reviewing the Vessel Health and Preservation (VHP) framework

CPD reflective questions

• What anatomical knowledge and patient assessment skills do you consider essential before attempting peripheral cannulation? How does this knowledge help in reducing the risks associated with this procedure?
• Can you recall a situation where you encountered anatomical variations or challenges during peripheral cannulation? How did you adapt your technique to account for these differences, and what lessons did you gain from this experience?
• How do you ensure the proper selection and utilisation of equipment, including the choice of cannulas and securement devices, during peripheral cannulation? Are there any recent advancements in equipment that you should be aware of and incorporate into your practice?
• In your practice, how do you effectively communicate with patients about the procedure, obtain informed consent, and provide them with information about potential risks and aftercare instructions? How can you improve your patient communication and education regarding peripheral cannulation?