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.
To minimize the chance of bacterial contamination, the blood must be drawn from an area free of skin lesions, and the phlebotomy site must be properly cleansed (Table 4.3). It is not possible to sterilize the skin, but steps are taken to greatly reduce the level of skin flora. A one‐step skin preparation using a chlorohexidine solution in 70% isopropanol is now recommended. Alternatively, a two‐step prep—scrubbing with a soap solution, followed by tincture of iodine or iodophor complex solution—may be used [1, 49, 50]. Preference for the prep method is often dependent on any history of donor allergies or previous reactions to the scrub. The selection of the venipuncture site and its sterilization are very important steps, because bacterial contamination of blood can be a serious, even fatal complication of transfusion (see Chapter 16).
Table 4.3 General procedure: donor arm preparation for blood collection.
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; then release tourniquet or cuff.Use a product combining 2% chlorhexidine gluconate in 70% isopropyl alcohol. Cover the whole area and ensure that the skin area is in contact with the disinfectant for at least 30 seconds.Allow the area to dry completely, or for a minimum of 30 seconds by the clock or as directed by the manufacturer.Whichever procedure is used, DO NOT touch the venipuncture site once the skin has been disinfected. |
Venipuncture
Most blood collection equipment uses 16‐ or 17‐gauge needles, and the entire set is closed and connected so that the needle is integral. The venipuncture is done with a needle that can be used only once to avoid contamination. The phlebotomist must be aware of the needle placement to minimize the likelihood of puncturing a nerve or artery.
Blood collection
Usually the blood container is placed on a scale, which may have a device to cut off the flow when the container reaches a set weight indicating that the desired volume of blood has been collected. The blood must flow freely and be mixed with anticoagulant frequently as it fills the container to avoid the development of small clots. Blood banks often use mechanical devices that continuously mix the blood and anticoagulant during phlebotomy. No more than 15% of the donor’s estimated blood volume should be collected, and the limit of 10.5 mL/kg body weight [1] is intended to meet this limit. In addition, the volume of blood in the container should be between 405 and 550 mL (i.e., 450 or 500 mL ± 10%). Thus, including specimens for testing, the amount of blood drawn could total 575 mL. Units containing 300–404 mL can be used for transfusion but must be labeled as low‐volume units. The amount of blood withdrawn must be within prescribed limits to be in the proper ratio with the anticoagulant, otherwise the blood cells may be damaged or anticoagulation may not be satisfactory (see Chapter 5).
The actual time for phlebotomy and bleeding is usually about 7 minutes and almost always less than 10 minutes. If the blood flow is slow, clots may form in the tubing before the blood mixes with the anticoagulant in the container. Although there is no FDA‐defined maximum allowable time for the collection of a unit of blood, most blood banks establish a maximum, usually no more than about 15 minutes. There is no difference in factor VIII or platelet recovery between units collected in less than 8 minutes versus those collected in 8–12 minutes [51]. Extremely rapid, pulsatile blood flow or the appearance of bright red blood may indicate an arterial puncture. This can be confirmed by feeling the pressure building in the blood container. An arterial puncture is nearly unmistakable because of the very rapid filling and pressure that develops in the blood container.
During blood donation, there is a slight decrease in systolic and a rise in diastolic blood pressure and peripheral resistance, along with a slight decline in cardiac output but little change in heart rate [52]. The regional cerebral oxygen saturation decreases significantly but still remains within the range of individual physiologic variation, while the cerebral tissue hemoglobin concentration increases significantly, probably because of an increase in cerebral blood volume, which appears to be the major compensation mechanism during acute blood loss to maintain cerebral oxygenation [53].
At the conclusion of blood collection, the needle is removed and the donor is asked to apply pressure to the vein in the antecubital fossa for at least 1 or 2 minutes. Many blood centers have a policy of asking the donor to raise his or her arm to minimize the venous pressure while pressure is applied to the vein. When there is no bleeding, discoloration, or evidence of a hematoma at the venipuncture site, the donor should be evaluated for other symptoms of a reaction to donation. If none is present, the donor can move off the donor table to the refreshment area. The donor should be observed during this time, because the movement into an upright posture may bring on lightheadedness or even fainting.
4.4 Postdonation care and adverse reactions to blood donation
Postdonation care
Many
