From Volume 49, Issue 5, May 2022 | Pages 388-392
Peripheral venous cannulation is a skill dentists may require in hospital jobs and sedation practice. This article provides a comprehensive overview of the technique, equipment, relative contraindications and potential complications.
CPD/Clinical Relevance: To act as an update and refresher for the dental team on peripheral venous cannulation.
Intravenous (IV) cannulation establishes a stable and reusable site of IV access for the short-term administration of medication and fluids. It is a skill frequently used by Dentists in hospital practice and is essential for all conscious sedation techniques other than inhalation sedation.1
Breast cancer-related lymphoedema can be provoked by venepuncture of the ipsilateral arm and most commonly occurs in patients who have undergone axillary lymph node clearance. It may also affect patients who have undergone sentinel node biopsy or radiotherapy to the axilla.2 Patients may or may not carry warning cards or bands to alert medical professional of axillary lymph node clearance so a thorough medical history is vital. In affected patients, the contralateral arm should be used for cannulation in the dental setting.
Sites of cannulation that are severely broken or inflamed should be avoided in order to prevent further damage and symptoms.
An arteriovenous fistula is a surgically created connection between an artery and vein. They represent the preferred choice of vascular access for patients requiring haemodialysis for renal replacement therapy. Arteriovenous fistulas are a lifeline for these patients and should not be cannulated or used for venepuncture. Additionally, the arm with the fistula should be avoided when measuring blood pressure to avoid any potential damage.3
In order to obtain valid consent for the procedure, clinicians should be able to describe the associated risks. Recognized risks include the following.
Haematoma or bruise formation is a common risk of venepuncture and is caused by the leakage of blood from a punctured vessel. A haematoma can appear as a swelling.4 This can occur during or after the procedure and can be minimized by applying firm pressure to the cannulation site following removal of the cannula. Bruising may occur more in failed cannulation sites, in friable older skin or in those patients with certain connective tissue diseases, vitamin deficiencies or bleeding disorders.5
This refers to the leakage of fluids into the surrounding tissues. It is commonly referred to as ‘tissuing’ and can result in swelling around the cannula site and pain on administration of fluid through the cannula. The term infiltration refers to the leakage of non-vesicant fluids or medications, and extravasation refers to the leakage of vesicant (can cause blistering or tissue injury) fluids or medications. With a pH of around 3.0, midazolam has the potential to cause tissue damage, but no side-effects have been reported in the literature.6
Thrombophlebitis is inflammation of the tunica intima lining of a vein. This may be recognized as pain, swelling, erythema and/or hardening around of the surrounding tissue. Causes may be mechanical, for example physical/mechanical trauma to the vein due to movement, perhaps due to cannulation over an area of flexion, or thrombophlebitis may have a chemical or bacterial cause. Other risk factors include older age, obesity, pregnancy, synthetic hormones, autoimmune disease (especially Behcet's and Buerger's disease) and certain coagulopathies (factor V Leiden mutation, deficiencies in antithrombin III, protein C and protein S).7
Catheter-related bloodstream infection (CRBI) is a rare, but serious, complication. It occurs when micro-organisms enter the blood stream via the indwelling cannula. Bacteria may be introduced during the cannulation procedure, and thus an aseptic technique is used. In inpatient settings, where patients may require intravenous access for the duration of their stay, a recent Cochrane review found no clear difference in rates of infection between routine replacement (every 72–96 hours) and when clinically indicated if thrombophlebitis was observed.8 However, dentists working in inpatient settings should refer to local policy.
While the patient may report pain during cannulation, they should not feel any discomfort once the cannula is in place, and when flushing the cannula with saline.
Venepuncture and peripheral cannulation have been associated with nerve injuries. These are mostly mild and temporary, but there are case reports in the literature of patients having sustained permanent and severe neuropathic pain that persists after needle removal.9 The median nerve and radial nerve both pass through the antecubital fossa and are at risk of damage during cannulation in this region.
Unintended arterial cannulation is a serious complication as arterial injection of drugs has the potential to cause peripheral ischaemia and tissue necrosis. Clinical signs may include severe pain, bright red pulsatile blood visible within the chamber of the cannula and blanching distal to the cannula.10 Most cases of accidental arterial cannulation involve radial artery branches of the forearm and hand, or are due to vascular abnormalities. The antecubital fossa is also a potential site for error owing to the close proximity to arteries in this region.6 If recognized, the cannula should be removed immediately, and pressure applied. The patient should be advised to expect bruising and post-operative instruction from the NHS Blood and Transplant Donor service recommend the RICE method (Rest, Ice, Compression and Elevation above the heart).11 If drugs have been administered, then this represents an emergency situation. The cannula should be left in situ and medical treatment should be sought urgently.
The basic equipment needed for cannulation is shown in Figure 1 and discussed in more detail below.
A sharps bin should be close to hand, and it may be useful to have a sterile container in which to keep the equipment until needed.
The appearance of a ‘good vein’ will be if it is straight, visible and easily palpable. The vein will feel bouncy and soft, indicating a large lumen and will refill when depressed. If the vein is well supported by surrounding soft tissue, it is less likely to move during cannulation.
The most common veins used for venepuncture are the metacarpal veins, located in the dorsum of hand, (Figure 2). They take blood to two larger veins in the antecubital fossa (ACF). The ACF is H-shaped and includes the cephalic vein, which lies laterally, and the basilic vein, which lies medially. The median cubital vein often unites the two main veins (Figure 3). Anatomy will vary between individuals, but usually, these are quite superficial. The operator must have a good knowledge of the related anatomy to maximize successful cannulation and avoid any complications such as unintentional puncture of an artery.
The antecubital fossa contains the brachial artery and radial and ulnar nerves (Figure 4). The brachial artery typically lies mesial to the biceps tendon; the tendon can be palpated by asking the patient to flex and extend the lower arm. The pulse of the brachial artery should be palpable medial to the biceps tendon.
Patient positioning is important for venepuncture. The patient should be semi-supine, preferably with their feet up in the dental chair.
The limb to be cannulated should be positioned below the level of the heart and, if possible, the patient can use muscle action to force blood into the veins by opening and closing their fist. Light tapping of the vein can be helpful as resultant histamine release results in vasodilation.14 The dental team can also provide invaluable support during venepuncture via distraction techniques (eg engaging in conversation with the patient) or assisting with clinical holding if required. Gauging individual patient needs and preferences beforehand is extremely beneficial, for example some patients like to be informed at every stage of venepuncture while others do not.
Before starting, the clinician must ensure that informed consent (or a best interest decision) has been obtained, all equipment is available, hand hygiene and donning of gloves is complete.
Although the insertion of an intravenous cannula is usually straightforward, there are instances when it can prove a challenge. Multiple attempts at cannulation can heighten anxiety and perception of pain, create stress for both the patient and dentist, and delay or prevent sedation or treatment.15 Factors, such as extremes of age, obesity, history of IV drug abuse, patients who have experienced repeated IV access due to their medical conditions or small, non-visible, non-palpable veins, can increase the complexity of the procedure. In some cases, modified techniques or the use of an adjunctive method may be necessary.
Application of heat results in vasodilation and can improve visibility of the vein for cannulation. Heat packs such as the single-use ‘DMI Sol-R Instant Heat Compresses’ (USA) can be purchased for use (Figure 5). This particular product should not be applied directly to the skin and so single-use paper towels can be used to wrap the compress or the patient may bring their own clean and thin towel to surgery. The heat from this product lasts for approximately 15 minutes.
If heat packs are not available, insulated gloves may be worn prior to the appointment. Alternatively, the patients' hand may be placed in a bowl of warm water to produce vasodilation.
Pre-procedural application of topical anaesthetic creams, such as EMLA (Eutectic Mixture of Local Anaesthetics, AstraZeneca, UK), has been proven to be effective at reducing discomfort associated with cannulation in both children and adults16 and may be particularly useful for highly anxious patients. Occlusive film dressings keep the cream over the site for sufficient time and should be provided by the dental team. Various formulations are available and need to be applied 30–60 minutes prior to cannulation for optimum effect (as per manufacturer instructions). However, creams can cause vasoconstriction, blanching and erythema, which may make cannulation more difficult.17
Another consideration is that some patients with cognitive disabilities may not tolerate the cream or dressings. It can therefore be helpful to explain the cream and dressings with imagery (eg alternative augmentive communication techniques) and/or to place gloves/bandages over the cream and dressings after application to prevent patients removing them.
A manual blood pressure cuff inflated to 60–80mmHg may be used as an alternative to a tourniquet18 and, anecdotally, may be more successful for some patients or operators. However, a recent randomized control trial showed no benefit over the use of a disposable elastic tourniquet.19
Vein finders such as Accuvein (AccuVein Inc, USA), Vasculuminator, (Pontes Medical, USA), VeinViewer (B Braun Medical Inc, Germany) and Veinsite (Vascular Solutions Inc, USA) are devices that emit an infrared laser light to detect superficial veins. An image of the veins is projected back onto the skin surface in real time improving the visualization of already visible/noticeable veins and allowing the identification of deeper veins. Evidence has shown that infrared vein finder technology improved general visibility of veins including in patients with obesity and those of African and Asian ethnicities.20
Ultrasound can be used to visualize vessels and can increase the likelihood of successful cannulation in patients with difficult venous access.21 The use of ultrasound for this purpose has grown in use in central venous cannulation, and may be an option that is accessible to clinicians working in hospital environments.
This article provides an update in peripheral venous cannulation for dentistry. The authors have outlined the indications, relevant anatomy of common cannulation sites, recommended equipment and additional aids to improve technique. Cannulation risks and relative contraindications have also been discussed.
