The Royal Marsden Hospital Manual of Clinical Nursing Procedures - Lisa Dougherty [411]
A number of vacuum systems are available that can be used for taking blood samples (Fig. 11.2). These are simple to use and cost-effective. The manufacturer’s instructions should be followed if one of these systems is used. Vacuum systems reduce the risk of healthcare workers being contaminated, because they offer a completely closed system during the process of blood withdrawal and there is no necessity to decant blood into bottles (Dougherty 2008). This makes them the safest method for collecting blood samples.
Blood collection tubes are available in various sizes and have different coloured tops dependent on the type of additives in the tube. The correct volume of blood should be collected into each tube to prevent erroneous results. The expiry dates on the tubes should also be monitored regularly.
Equipment available will depend on local policy (Table 11.2), but with increasing concern about the possibility of contamination to the practitioner, blood collection systems with integrated safety devices are now readily available and should be used wherever possible (Garza and Becan-McBride 2010). However, the nurse must always select the device after assessing the condition and accessibility of the vein.
Table 11.2 Choice of intravenous device
Pharmacological support
It is important to remember that patients may fear venepuncture and in some cases suffer from severe needle phobia. The use of topical local anaesthetic cream may be beneficial for anxious patients or for venepuncture in children (Weinstein and Plumer 2007).
Non-pharmacological support
Patient anxiety about the procedure may result in vasoconstriction. The nurse’s manner and approach will also have a direct bearing on the patient’s experience (Garza and Becan-McBride 2010). Approaching the patient with a confident manner and giving adequate explanation of the procedure may reduce anxiety. Careful preparation and an unhurried approach will help to relax the patient and this in turn will increase vasodilation (Dougherty 2008, Weinstein and Plumer 2007).
Specific patient preparation
Injury, disease or treatment, for example amputation, fracture and cerebrovascular accident, may prevent the use of a limb for venepuncture, thereby reducing the venous access. Use of a limb may be contraindicated because of an operation on one side of the body, for example mastectomy and axillary node dissection, as this can lead to impairment of lymphatic drainage, which can influence venous flow regardless of whether there is obvious lymphoedema (Berreth 2010, Cole 2006, Ernst 2005, Hoeltke 2006).
The age and weight of the patient will also influence choice. Young children have short fine veins, and the elderly have prominent but fragile veins. Care must be taken with fragile veins and the largest vein should be chosen along with the smallest gauge device to reduce the amount of trauma to the vessel. Malnourished patients will often present with friable veins (Dougherty 2008).
If the patient is in shock or dehydrated there will be poor superficial peripheral access. It may be necessary to take blood after the patient is rehydrated as this will promote venous filling and blood will be obtained more easily (Dougherty 2008).
Medications can influence the choice of vein in that patients on anticoagulants or steroids or those who are thrombocytopenic tend to have more fragile veins and will be at greater risk of bruising both during venepuncture and on removal of the needle. Therefore choice may be limited by areas of bruising present or the inability to access the vessel without causing bruising (Dougherty 2008).
The temperature of the environment will influence venous dilation. If the patient is cold, no veins may be evident on first inspection. Application of heat, for example in the form of a warm compress or soaking the arm in warm water, will increase the size and visibility of the veins, thus increasing the likelihood of a successful first attempt (Lenhardt et al. 2002, Weinstein