Anatomy and physiology of the venous blood system and upper limb

Principles of ‘Infection prevention and control’ (seep. 151) with respect to blood-borne infection

Different devices used in venepuncture

Available local guidelines for venepuncture

Understanding of routine blood investigations and their results.

Venepuncture is carried out in order:

Venepuncture is performed by a medical practitioner or phlebotomist, or by a qualified nurse who has undertaken specialised education and is competent in this practice. The non-specialist nurse may be asked to assist with this procedure.

Blood can be withdrawn from the vein using a closed venepuncture system, a needle and syringe, or alternatively a butterfly infusion set, which may be more appropriate for some elderly patients. The closed system for venepuncture may utilise a vacuum effect to facilitate ease of blood withdrawal or may still require the practitioner to pull back a plunger to receive blood flow. The condition of the patient’s veins will help determine the appropriate device for the collection of blood (Lavery & Ingram 2005). The practitioner may experience difficulty in gaining venous access in patients for whom venepuncture is a frequent occurrence, e.g. blood monitoring in relation to drug therapy (chemotherapy; warfarin; anti-rheumatics). Veins in the obese patient or the frail elderly may either be difficult to palpate or may collapse on introduction of the needle.

The value of the closed system is that several different samples may be taken as only the tube (rather than the syringe, as may be necessary in the traditional method) needs to be changed, thus protecting the nurse from blood spillage. There is also a reduced risk of needlestick injury because blood flows directly from the vein to the specimen bottle and does not have to be transferred to individual containers.

Prior to discussing the equipment required it is pertinent to present the differing opinions in relation to infection control guidelines and skin cleansing prior to venepuncture. There is a lack of recent research to guide practitioners, however for skin cleansing to be effective the skin must be rubbed with an alcohol- impregnated swab for at least 30 seconds prior to insertion of a needle then left to dry for 30 seconds (Black & Hughes 1997). This rubbing and use of alcohol may cause localised skin irritation and some practitioners suggest that infection rates are unchanged if the skin is not cleansed, although again this remains anecdotal due to the dearth of evidence-based practice. The practitioner must therefore decide if this procedure is necessary within each situation where venepuncture occurs, while respecting local infection control policies.