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Evidence‐based approaches

Rationale

Indications

Venepuncture is carried out for two reasons:

to obtain a blood sample for diagnostic purposes
to monitor levels of blood components and a patient's condition (Garza and Becan‐McBride [66]).

Contraindications

Contraindications to using certain veins or limbs include:

previous surgery to an affected limb with axillary lymph node clearance
lymphoedema on a particular limb
amputation, fracture or cerebrovascular accident affecting a limb.

Methods of improving venous access

There are various ways of improving venous access:

Application of a tourniquet promotes venous distension. The tourniquet should be tight enough to impede venous return but not restrict arterial flow. It should be placed about 7–8 cm above the venepuncture site. It may be more comfortable for the patient to position it over a sleeve or paper towel to prevent pinching the skin. The tourniquet should not be left on for longer than 1 minute as this may result in haemoconcentration (pooling of the blood) or haemolysis (rupturing of red blood cells), leading to inaccurate blood results (Hoeltke [88]).
The patient may be asked to clench their fist to encourage venous distension but should avoid ‘pumping’ as this action may affect certain blood results (e.g. test for potassium levels, as cell damage releases potassium) (Garza and Becan‐McBride [66]).
Lowering the arm below heart level increases blood supply to the veins.
Light tapping of the vein may be useful but can be painful and may result in the formation of a haematoma in patients with fragile veins, for example thrombocytopenic patients (Dougherty [53]).
The use of heat in the form of a warm pack or by immersing the arm in a bowl of warm water for 10 minutes helps to encourage vasodilation and venous filling (Garza and Becan‐McBride [66]).
Ointment or patches containing small amounts of glyceryl trinitrate can be used to improve local vasodilation to aid venepuncture (Weinstein and Hagle [252]).

Methods of insertion

Asepsis is vital when performing a venepuncture as the skin is breached and a foreign device is introduced into a sterile circulatory system. The two major sources of microbial contamination are:

cross‐infection from practitioner to patient
skin flora of the patient.

Good hand washing and drying techniques are essential and gloves should be changed between patients (see Chapter c04: Infection prevention and control).

To remove the risk presented by the patient's skin flora, firm and prolonged rubbing with an alcohol‐based solution, such as chlorhexidine 2% in 70% alcohol, is advised (RCN 2017b). This cleaning should continue for a minimum of 30 seconds, although some authors state a minimum of 1 minute or longer (Weinstein and Hagle [252]). The area that has been cleaned should then be allowed to dry. This facilitates coagulation of the organisms, thus ensuring disinfection, and also prevents a stinging pain on insertion of the needle due to the alcohol being transferred onto the end of the needle. The skin must not be touched or the vein repalpated prior to venepuncture (McCall and Tankersley [138]).