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A minimum transfusion trigger has not been well established because of the variability of patient co-morbidities and anaemia tolerance. Evidence suggests that most patients can safely tolerate anaemia of 7 g/dL of Hb in the absence of active bleeding (Tolich 2008). However, surveys of the UK population show that most blood recipients are relatively elderly; many will have cardiovascular disease and may be less tolerant of low haemoglobin levels than younger, fitter patients. A low transfusion threshold may therefore be unwise, as older patients may also be at greater risk of congestive cardiac failure due to volume overload when blood and other fluids are infused (Blood Safety and Quality Regulations 2005, McClelland 2007).

Blood donation and testing

All blood donated in the UK is given voluntarily. The successful selection of a donor must protect them from any harm that may be caused by the donation process and also protect the possible recipient of products derived from the donor’s blood. Donors of blood for therapeutic use should be in good health; if there is any doubt about their suitability, the donation should be deferred and they should be fully assessed by a designated medical officer. All donors of blood or its components (via apheresis) should be assessed in accordance with the Joint UKBTS/NIBSC Professional Advisory Committee (JPAC) donor selection guidelines (JPAC 2007). The assessment of fitness to donate includes a questionnaire relating to general health, lifestyle, past medical history and medication. Donation may be temporarily or permanently deferred for a variety of reasons including cardiovascular disease, central nervous system diseases, malignancy and some infectious diseases, all of which are detailed in the JPAC 2007 guidelines. Donors are also screened for risk of exposure to transmissible infectious diseases, and specific guidance is provided for donors receiving therapeutic drugs.

Prevention of transmission of infection is determined by donor selection criteria and laboratory testing. In the UK, all blood donations are tested for infections which could be passed on to the recipient. However, concern about transfusion-related variant Creutzfeldt–Jakob disease (vCJD) transmission is now supported by clinical evidence (Ludlam and Turner 2006) and, despite continuing research, a screening test for preclinical human infection has yet to be developed (Brown 2005). Therefore, donor exclusion criteria remain an important precautionary measure (Cervenakova and Brown 2004). When a donor has been successfully screened, they must validate the information they have provided and record that they have given consent to proceed.

Autologous donation

Since the 1980s there has been interest in autologous donation (blood and blood components collected from an individual and intended solely for subsequent autologous transfusion to that same individual) (Blood Safety and Quality Regulations 2005). This has largely been attributed to high-profile infection risks: human immunodeficiency virus (HIV), hepatitis C and more recently vCJD (James and Harrison 2002). However, autologous donation is not risk free, with 28 cases of adverse events being reported to SHOT in 2008, the majority of which arose through cell salvage events. Autologous donation is contraindicated in certain circumstances. Furthermore, there has been significant concern about the efficacy of some methods (Carless et al. 2004, Henry et al. 2002). Three principal methods of autologous donation exist.

Preoperative autologous donation (PAD)

This requires the patients to donate up to four units of blood whilst simultaneously taking iron supplements in the month preceding surgery. However, the efficacy of this method has been questioned by systematic review (Henry et al. 2002) and is only indicated in very specific circumstances such as patients with very rare blood types, patients donating bone marrow and fit patients who have a significant fear of receiving