The advantages of using a peripheral cannula are that they are usually easy to insert and have few associated complications; however, they are associated with phlebitis (either mechanical or chemical) and require constant re‐siting (Dougherty [124], Gorski et al. [181], RCN [381]).

The insertion of a peripheral intravenous cannula (PIVC) is the most common invasive clinical procedure performed in hospitals worldwide (Ahlqvist et al. [2], Alexandrou et al. [6], Webster et al. [464]). Despite their prevalence, PIVCs are associated with high rates of complication, including insertion difficulty, phlebitis, infiltration, occlusion, dislodgement and catheter‐related bloodstream infection (CRBSI), all of which are known to increase morbidity and mortality rates (Alexandrou et al. [5], [6]). Recent VAD prevalence audits demonstrate substantial concerns with everyday practice, particularly relating to redundant devices, insertion site complications, substandard dressings, and documentation of site assessment and flushing practices (Ray‐Barruel et al. [379]). The One Million Global Catheters study (Alexandrou [3]) assessed the prevalence of PIVCs and their management practices worldwide and reported that 59% of patients in hospital had at least one PIVC in place and 16% had other types of VAD. The prevalence of idle PIVCs was 16%, and 12% of those had at least one symptom of phlebitis (Alexandrou et al. [5]). Failure and complications of PIVCs commonly result in premature removal and replacement as well as increased patient pain and anxiety, particularly in patients with difficult venous access (Carr et al. [63]). Up to 90% of PIVCs are prematurely removed owing to failure before planned replacement of the device or before intravenous therapy has been completed (Alexandrou et al. [6]), resulting in increased healthcare costs associated with increased length of hospital stay (Alexandrou et al. [5], [6], Wallis et al. [461]). There are evidence‐based guidelines and standards of practice (Gorski et al. [181], RCN [381]) to assist clinicians in managing these devices while reducing PIVC failure rate (Alexandrou et al. [5], [6]). Reports suggest that a team approach to the assessment, insertion and maintenance of VADs improves clinical outcomes, patient experience and healthcare processes (Carr et al. [64], Johnson et al. [233]).

Difficult peripheral access is traumatic for patients. Application of a tourniquet, tapping and stroking of veins, vigorous swabbing, clenching the hand to pump up veins, hanging the forearm downwards and application of local warmth are all commonly used aids for cannulation (Berreth [30], Dougherty [124]).

The application of a tourniquet promotes venous distension. The tourniquet should be tight enough to impede venous return while not affecting arterial flow (Garza and Becan‐McBride [170], Perucca [369], RCN [381]). There is strong evidence that reusable tourniquets are associated with the increased risk of infections such as MRSA (meticillin‐resistant Staphylococcus aureus) (Elhassan and Dixon [138]), and, as such, the use of disposable tourniquets is recommended. The tourniquet should be applied around the upper forearm about 15–20 cm above the venepuncture site (McCall and Tankersley [303]) to promote dilation of the veins, and time should be allowed for the veins to fill. However, too tight application (particularly in older patients) can result in petechiae at the site of the tourniquet, haematoma, general bruising or venous high‐pressure backflow of blood, resulting in vein ‘blows’ (Moureau [327]). To help reduce this, the tourniquet should be applied over clothing wherever possible (Hoeltke [215], Toth [445], Weinstein and Hagle [465]) or using a blood pressure cuff placed upside down and inflated just below diastolic pressure for effective compression. It may also be possible in some patients to avoid a tourniquet altogether by compressing a superficial vein with a finger above the insertion site (Dougherty [127]). Light tapping of the vein may be useful as this releases histamines beneath the skin and causes dilation (Frank [157], Phillips [371]), but it can be painful and may result in the formation of a haematoma; again, older patients and those with fragile veins are most at risk (Garza and Becan‐McBride [170], Witt [475]). Other methods used to improve venous distension include lowering the extremity below the level of the heart and opening and closing the fist (the action of the muscles forces blood into the veins, causing them to distend) (Frank [157], Phillips [371]).

When these methods fail, applying a warm compress in the form of a heat pack, warmed towels or electric heating blanket, or immersing the limb in a bowl of warm water for 10–15 minutes, helps to increase vasodilation and promote venous filling (Chen [70], Fink et al. [148], Weinstein and Hagle [465]). Ointments or patches containing small amounts of glycerol trinitrate have been used to improve vasodilation (Frank [157], Gunwardene and Davenport [189]) as well as to reduce the incidence of chemical phlebitis and increase site survival time (Hecker [207]).

Skin stabilization is one of the most important elements of successful cannulation (Dougherty [124], Frank [157], Perucca [369]) (Figure 17.12). Superficial veins tend to roll; to prevent this, the vein must be stabilized by applying traction to the side of the insertion site or below it, using the practitioner's non‐dominant hand. This also facilitates a smoother needle entry. Various methods are used (Dougherty [124]):

Stabilization of the vein must be maintained throughout the procedure until the needle or cannula is successfully sited. If the tension is released halfway through the procedure, the needle may penetrate the opposite wall of the vein, resulting in the formation of a haematoma (De Verteuil [110], Dougherty [124]).

It is important that the needle enters the skin with the bevel up, as this results in a smooth venepuncture as the sharpest part of the needle will penetrate the skin first, and it also reduces the risk of piercing the posterior wall of the vein (Weinstein and Hagle [465]). The angle at which the needle enters the skin varies with the type of device used and the depth of the vein in the subcutaneous tissue, from 10° to 45° (Dougherty [124], Perucca [369], Weinstein and Hagle [465]). Once the device is in the vein, the angle should always be reduced in order to prevent puncture of the posterior wall of the vein (Perucca [369]).

There are two main methods of approaching the vein:

When blood appears in the chamber of a cannula, this is known as ‘flashback’ and it indicates that the initial entry into the vein has been successful. This may be accompanied by a ‘giving way’ sensation felt by the practitioner, which occurs because resistance from the vein wall decreases as the device enters the lumen of the vein. This usually occurs with thicker‐walled cannulas (De Verteuil [110], Weinstein and Hagle [465]). If the device punctures the posterior wall, the flashback will stop. However, the flashback may be slow with small‐gauge cannulas or hypotensive patients.

The cannula should be advanced gently and smoothly into the vein, and practitioners use a number of techniques to achieve this. One method, which provides the least risk of through‐puncture but can be difficult to learn initially, is the one‐handed technique (De Verteuil [110], Frank [157], Perucca [369]). The same hand that performs the cannulation also withdraws the stylet and advances the cannula into the vein. This allows skin traction to be maintained while the device is advanced, and in older patients it also allows the practitioner to draw loose thick skin downward from underneath by using the hand in a ‘C clamp’ position (Rosenthal [386]). If one hand is not used to apply traction, then on cannula advancement there may be unnecessary damage to the endothelium, resulting in phlebitis (Hadaway [194]). This technique is also more suited to older patients (Hadaway [192], Perucca [369], Weinstein and Hagle [465]) because the connective tissue that anchors superficial veins is reduced with ageing and this makes veins more likely to roll, so it is important to firmly anchor older adult veins (Rosenthal [386]).

In the one‐step technique, after the cannula has entered the vein, the practitioner slides the cannula off the stylet in one movement. The disadvantage of this method is that the stylet must remain completely still in order to prevent damage to the vein. It is best accomplished on a straight vein and when the cannula has a small fingerguard, which can be used to ‘push’ the cannula off (Dougherty [124]).

In the two‐handed technique, the practitioner performs the cannulation with one hand but releases the skin traction in order to advance the cannula off the stylet. This method prevents blood spill; however, as it necessitates the release of skin traction, it can often lead to puncturing of the vein wall (Dougherty [124]).

If the cannulation is unsuccessful, the stylet should not be reintroduced as this could result in catheter fragmentation and embolism (Perucca [369]). A practitioner should not make more than two attempts at cannulation before passing the patient on to a more experienced colleague (Dougherty [124], Gorski et al. [181], Perucca [369]).

The patient will receive their intravenous therapy and have a cannula placed that is comfortable and in a convenient position, enabling them to continue their daily activities. It will be secured and dressed to prevent any complications.