Transfusion Medicine - Jeffrey McCullough

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used [32]. Noninvasive methods for hemoglobin are now available but have not yet become widely used. For any method, the recommended blood drop source is the finger, because blood from an earlobe puncture can have a falsely elevated hemoglobin [33, 34]. Factors that affect the rate of deferrals due to hematocrit are the proportion of female donors, smokers, African Americans in the donor population, altitude of the donation location, and source of blood sample (finger versus ear lobe). Because the hemoglobin fluctuates with temperature, being lower in hot weather, there may be an increase in deferrals because of low hemoglobin during the summer months [35]. Until recently, the same hemoglobin criterion was used for men and women (12.5 g/dL). This is within the normal range for Caucasian women [11.6–15.7 g/dL) but below the normal range for Caucasian men (13.3–17.2 g/dL). Most hemoglobin deferrals occurred in women, although many women with essentially normal hemoglobins have been deferred. In contrast, a hemoglobin of 12.5 g/dL may indicate mild anemia in a man. Although FDA guidance now recognizes that many women may safely donate with hemoglobin 12–12.5 g/dL, it also recommends that further, although unspecified, steps to prevent iron deficiency be taken if this lower cutoff is used because iron deficiency is prevalent in premenopausal women who are frequent whole blood donors [36, 37]. The screening hemoglobin values do not prevent iron‐deficient individuals (predominantly women) from donating [36, 38].

      Low or absent iron stores occur in a significant percentage of frequent blood donors. Suggested approaches include further restrictions on the frequency of blood donation and/or providing iron supplementation. There is no uniform approach to donors deferred because of low hemoglobin. Approaches have included temporary deferral for 6 months, 3 days to 3 months, or variable length of deferral depending on the hemoglobin. There are no standard recommendations regarding serum ferritin testing and whether to provide iron supplementation or merely recommend this to the donors [39, 40]. Some blood centers have implemented programs to perform ferritin testing, which is considered a more reliable indication of iron status. These programs often focus on young donors, especially females who may be most susceptible to the effects of iron depletion [41, 42]. Two studies [43, 44] support the value of iron therapy in women without anemia.

      Even in the absence of anemia, iron deficiency can have clinical effects, such as fatigue, decreased exercise capacity, and cognitive performance [45]. Strategies ranging from physician referral to providing educational material or even providing iron supplements have been tried, but no standard approach is in wide use. This has been an issue for years and could have major implications for donor availability [38, 39, 45].

      Special blood donations

      There are several situations involving blood donation in which the blood may be collected by the donor center but will not be used as part of the community’s general blood supply. Examples of these include autologous donation, directed donation, patient‐specific donation, and therapeutic bleeding. In some of these situations, the FDA requirements for blood donation may not apply. However, if directed donations are not needed by the designated patient and would otherwise meet criteria for general blood supply use, it is possible for a hospital to make these units available for others to use.

      Labeling

      The first step in the collection process is labeling of all containers, tubes, and related materials. This is an extremely important step because it relates all tubes, specimens, documents, and components to the identity of the donor. Virtually all blood banks use bar‐coded labels that are intended to meet international industry standards for labeling (ISBT 128) consistent with FDA and AABB requirements [46]. Related tracking of specimens, test results, and individual components can be managed by computers using these labels. Computer systems are generally used to accumulate all data relevant to the individual donation to determine whether the components are suitable for transfusion and can be released into usable inventory. Thus, there are detailed and specific steps in the process at the donor bedside to ensure the accuracy of all labels.

      Blood bags

      Blood must be collected into FDA‐licensed containers, each of which is sterile and can be used only once. The containers are made of plasticized material that is biocompatible with blood cells and allows diffusion of gases to provide optimal cell preservation (see Chapter 5). These blood containers are combinations of multiple bags connected by tubing so that components can be transferred between bags without being exposed to air. This is referred to as a “closed system.” This system of separation of the whole blood into its components in a closed system thus minimizes the chance of bacterial contamination while making it possible to store each component under the conditions and length of time that are optimum for that component. Because some bacteria can enter the blood bag from skin at the venipuncture, most blood collection sets now contain a small pouch for diversion of the first few milliliters of blood, which is used for many standard tests. Diversion of the first few milliliters of blood collected can reduce the bacterial contamination rate from 46% to 71% [47, 48].

      Anticoagulant preservative solutions

      Several anticoagulant preservative solutions are available. The anticoagulants are various formulas of citrate solutions. The blood may be stored in these solutions and used for transfusion, or most of the supernatant may be removed and the cells stored in other “additive” solutions. The composition and effects of these anticoagulant and preservative solutions are discussed more completely in Chapter 5.

      Selection of the vein and preparation of the venipuncture site

      Blood is drawn from a vein in the antecubital fossa. The vein selected should be large enough to accommodate approximately a 16‐gauge needle. Careful selection of the vein makes the venipuncture quick and easy, thus providing good blood flow and a quality component but also minimizing the discomfort to the donor and making the donation experience as pleasant as possible. The choice of the vein will also minimize the likelihood of inadvertently damaging a nerve or puncturing an artery (see the later Adverse Reactions section). A blood pressure cuff is usually used to impede venous return and distend the vein.

      Source: World Health Organization. WHO Guidelines on Drawing Blood: Best Practices in Phlebotomy. Geneva: World Health Organization, 2010. © 2010 World Health Organization.

Apply tourniquet or blood pressure cuff. Identify venipuncture site;

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