Mollison's Blood Transfusion in Clinical Medicine

Harvey G. Klein, David J. Anstee

• Publisher: Wiley-Blackwell
• Year: 2013
• ISBN:
  9781118689974
• Edition: 12
• Topic: Medicine
• Subtopic: Hematology

Mollison's Blood Transfusion in Clinical Medicine is an icon in the field of transfusion and the first edition was published in 1951. The book arose from the concept of the transfusionist, as both scientist and expert consultant. For many years, this text has provided the primary, and often the sole, reference for detailed information and practical experience in blood transfusion. The book iscompletely revised and updated throughout to include the latest advances and developments in the field.

1

Blood Donors and the Withdrawal of Blood

Bloodletting was once the treatment for almost all maladies and, when carried out in moderation, caused little harm. This chapter includes a discussion of therapeutic phlebotomy, but is mainly concerned with the withdrawal of blood or its constituent parts from healthy donors for transfusion to patients. The chapter addresses qualification of the donor, statistics regarding collection and use, blood shortages and conditions that disqualify donors. Complications of blood donation including iron loss, syncope and needle injuries, and other less common adverse events are discussed. Some applications of therapeutic phlebotomy and blood withdrawal during neonatal exchange transfusion are outlined.

Blood Donation

The Blood Donor

General Qualifications

Qualification of blood donors has become a lengthy and detailed process, a ‘donor inquisition’ some would say. Yet blood collection depends on this system of safeguards to protect the donor from injury and the recipient from the risks of allogeneic blood (see Chapters 15 and 16). Sensitive screening tests have been considered the cornerstone of blood safety for more than four decades. However, testing represents only one component of this system. Additional ‘layers of safety’ include detailed donor education programmes prior to recruitment, pre-donation informational literature, stringent donor screening selection and deferral procedures, post-donation product quarantine, and donor tracing and notification when instances of disease transmission are detected. Each element plays a role in preventing ‘tainted’ units from entering the blood inventory. Most transfusion services use evidence-based standards and regulations for the selection of donors, such as those published in the AABB ‘Standards’ and the United Kingdom ‘Red Book’, (UKBTS/NIBSC Liaison Group 2005; AABB 2012) and quality systems to assure excellence in all phases of their application (Roback 2008). Other standards derive from ‘expert opinion’ and ‘common sense’; these latter policies need to be revisited as scientific information becomes available.

Blood donors should have the following general qualifications: they should have reached the age of consent or an age judged suitable by local regulation, most often 18 years, but lower in some countries such as the USA and the UK; donors should enjoy good health, have no history of serious illness, weigh enough to allow safe donation of a ‘unit’ and not recognize themselves as being at risk of transmitting infection (see below). Ideally, donation should be strictly voluntary and without financial incentive (see Chapter 16); however emerging evidence from studies in Sub-Saharan Africa suggests that in some developing countries, the prevalence of markers for HIV, HCV and HBV is the same for family-replacement donors as for voluntary non-remunerated donors. Some blood services impose an arbitrary upper limit on age, commonly 65 years; however, it seems curiously subjective to exclude donors on the basis of age alone if they are otherwise in good health (Schmidt 1991; Simon et al. 1991). Furthermore, it is the younger donor who is at increased risk of reactions following phlebotomy (Eder et al. 2008). The Blood Collection Service should provide informational literature for prospective blood donors. After information and counselling about criteria for donor selection, donors should consent in writing to the terms of donation, including the use of the donated blood, the extent of testing, the use of testing results (including donor notification of positive results) and the future use of any stored specimens. Donors should be told about the possibility of delayed fainting and about other significant risks of the donation procedure.

Blood donation has potential medicolegal consequences. If a donor becomes ill shortly after giving blood, the illness may be attributed to blood donation. For this reason, among others, it is important to ensure that donors have no history of medical conditions such as brittle diabetes, hypertension, poorly controlled epilepsy and unstable cardiopulmonary disease that might be associated with an adverse event following phlebotomy. Pregnancy might be adversely affected by the donation process and ordinarily excludes a donor. Donors who become ill within 2 weeks of donation should be encouraged to inform the transfusion service, which may wish to discard the donated blood, recall any plasma sent for fractionation or follow up recipients of the blood components as appropriate. Donors who develop hepatitis or HIV infection within 3–6 months of donation should certainly inform the Blood Collection Service.

Donor Interview – an Evolving Inquisition

The donor interview, once an informal set of locally-derived questions administered by well-intentioned volunteers, has become an increasingly detailed set of validated questions designed to qualify the ‘raw material’ of blood components. The process is highly regulated. Interviewers must be trained and qualified to administer questions and evaluate responses. Screening should be conducted in a setting sufficiently unhurried and private as to permit discussion of confidential information. With current practices in the USA, approximately 2% of volunteer donors still disclose risks that would have led to deferral if known at the time of donation (Sanchez et al. 2001). Non-disclosure of deferrable risks is complex. Donors may rationalize failure to acknowledge distant risk behaviour or may truly misinterpret screening questions. Some degree of non-disclosure is probably an inherent part of pre-donation screening (Glynn et al. 2001; O’Brien et al. 2009). Introduction of standardized and validated questionnaires and the application of interactive computer-assisted audiovisual health history may reduce errors and misinterpretations during conduct of the donor interview (Zuck et al. 2001).

Physical Examination

Blood collectors perform a limited physical examination designed to protect donor and recipient. Screeners routinely assess the donor’s general appearance and defer those who do not appear well or are under the influence of alcohol. Pre-donation pulse and blood pressure in the ‘normal range’ are often used as screening standards, although variances have been granted for healthy athletes. The scientific rationale supporting specific values for pulse and blood pressure is surprisingly weak and may not predict or prevent cardiovascular or cerebrovascular events in prospective blood donors (see below). Blood collectors are re-evaluating the usefulness of these screening measures. Body weight and temperature are measured by some collection services. Both arms are examined for evidence of illicit drug use and for lesions at the venepuncture site.

Volume of Donation

The volume of anticoagulant solutions in collection bags is calculated to allow for collection of a particular volume of blood, which, in the UK, is 450 ± 45 ml. In the USA often 500 ml, but in no case more than 10.5 ml/kg including the additional volume of 20–30 ml of blood collected into pilot tubes. There is concern that even these volumes may contribute to delayed fainting in smaller donors. From donors weighing 41–50 kg, only 250 ml of blood is collected into bags in which the volume of anticoagulant solution has been appropriately reduced. In some countries, the volume collected routinely is less than 450 ml, for example 350–400 ml in Turkey, Greece and Italy, and 250 ml in some Asian countries such as Japan, where donors tend to be smaller. Commercial plasma collectors routinely weigh the donor and calculate a safe volume based on the estimated blood volume.

Record-Keeping

It should be possible to trace the origin of every blood donation and records should be kept for several years, depending on the guidelines for each country. In many countries, a system employing unique bar-coded eye-readable donation numbers is now in use. This system makes it possible to link each donation to its integral containers and sample tubes and to the particular donor session record. Information concerning previous donations, such as records of blood groups and microbiology screening tests, antibodies detected, donor deferrals and adverse reactions are important for subsequent attendances. Electronic storage of donor information greatly facilitates accurate identification, release, distribution and traceability of units of blood and blood products. An international code, ISBT 128, is intended to be used by all countries for the accurate identification of donors and donations (Doughty and Flanagan 1996). These records must be protected from accidental destruction, modification or unauthorized access.

Frequency of Donors in the Population

Although in many Western countries, some 60% of the population consists of healthy adults aged 18–65 years and thus qualified to be blood donors, the highest annual frequency of donation in the world corresponds to about 10% of the population eligible to give blood donating once per year, as in Switzerland (Linden et al. 1988; Hassig 1991). The frequency in most developing countries is less than 1% (Leikola 1990).The number of units collected per 1000 US inhabitants of usual donor age (18–65) was 84.1 in 2006, 88.0 in 2001, and 80.8 in 1999. Although these numbers compare favourably with the rate of 72.2 per 1000 in 1997, they pale in comparison with the 100 units per 1000 population collected in Switzerland. As treacherous as it may be to interpret these figures, the numbers suggest that US collecting facilities are generally improving efficiency. Data from the American National Red Cross indicate that the average volunteer donates about 1.7 times a year. Losses from outdated red cells accounted for 5.3% of the supply but, given the fact that red cells can be transfused only to compatible recipients, the number of usable units outdated appears to be extremely small. More than 99% of group O units and 97% of group A units were transfused (National Blood Data Resource Center 2001, 2007 National blood Collection and Utilization Survey).

Blood Utilization and Shortages

Despite the constant rise in collections, blood collectors report frequent shortages and emergency appeals for blood are disturbingly common. Some 16 million units of red cells and 13 million units of platelets are collected annually in the US and the numbers continue to rise (2007 National blood Collection and Utilization Survey). With the current shelf life, the blood supply more closely resembles a pipeline than a bank or reservoir. A few days of under collection can have a devastating effect on supply. Although most national supermarket chains have developed efficient bar code-based information systems to monitor perishable inventory on a daily basis, few national blood services have as accurate an accounting of blood component location and availability by group and type. Furthermore, there is little general agreement about what constitutes a shortage. Measures of postponed surgery and transfusion, as well as increased rates of RhoD-positive transfusions to RhoD-negative recipients provide some indication of shortage at the treatment level. In a national survey in the US in 2006, 6.9% of hospitals surveyed reportedly delayed elective surgery for 1 day or more, and 13.5% experienced at least 1 day in which non-surgical blood needs could not be met (National Blood Collection and Utilization Survey 2007). A separate government-sponsored study revealed seasonal fluctuations of blood appeals and cancellations of surgery for lack of platelet transfusion support (Nightingale et al. 2003). In the former survey, red cell transfusion reached an all-time high, an increase of more than 30% during the previous nine years.

Blood utilization in the US approached 49 units per 1000 of the population, a number not different from that of the previous two surveys and a suggestion that red cell use may have reached a steady-state. However demographics in developed countries are changing and with them, patterns of donation and usage. Ordinarily, more blood is donated by younger age groups, whereas more is used by the elderly (Cobain et al. 2007). The shift to older donors mirrors the aging of the population (Zou et al. 2007). In Finland, 70- to 80-year-olds have an eightfold higher RBC consumption than 20- to 40-year-olds (Ali et al. 2009). The US decennial census 2000 projects that, by the year 2030, the population of Americans over the age of 65 will increase from 12% to 20%; this figure will be even higher in most countries in Western Europe (Kinsella and Velkoff 2001). Variation in RBC use per capita among countries can be explained largely by the age distribution differences of the populations rather than by the different national treatment standards. Given these projections, developed countries may expect blood shortages to become a way of life, unless substantial resources are invested in donor recruitment and retention or methods are adapted to serve the changing population demographic. In developing countries, this is already the case.

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