Whole blood

Approximately 75 million units of whole blood are collected worldwide, but this almost certainly does not meet worldwide needs. The organizations and systems that collect and provide blood vary greatly throughout the world. Most developed countries, with the exception of the United States, have some form of a national blood program.³ The program may be operated by that country’s Red Cross or by its government. The extent to which this program is structured, the mechanisms of funding, and the effectiveness of the national blood program in meeting the total blood needs for that country also vary greatly throughout the world. In many developing countries the blood supply may be inadequate to meet the needs, and the blood that is available has a high likelihood of transmitting infectious disease.⁴

The US blood system is operated by multiple organizations.⁵ Approximately 15 million units of whole blood are collected each year primarily in regional or community blood centers.⁶ Hospitals collect less than 10% of the US blood supply. The American Red Cross is the largest blood collecting organization in the US, accounting for about 45% of the blood supply. Other regional or community blood centers are non-profit organizations governed by local volunteer boards of directors.

It is policy of the International Society for Blood Transfusion and the World Health Organization that blood should be donated voluntarily. The reason for advocating volunteerism in blood donation is not only based on the moral principle of not selling body parts or tissues but also because blood from paid donors has a much higher risk of disease transmission.⁷ When a financial payment is involved, there is an incentive for the potential donor to be dishonest about his or her medical history. Despite the increased sophistication of laboratory testing of donated blood, some infectious units of blood will not be detected by present tests.⁸ Thus, if the donor is dishonest about his or her medical history, there is more likelihood that the unit may be infectious.

In developed countries, the collection, processing, testing and preparation of blood components is subject to some form of regulation. Although blood is a biological, and thus different from a pharmaceutical, some form of pharmaceutical-type regulation is applied.⁵ Thus, there are requirements for donor eligibility, laboratory testing of donated blood, blood preservation and the minimum content of various blood components. Usually these requirements define procedures, records, staff proficiency, specific testing and donor medical requirements that blood banks must follow. In the US, additional standards have been promulgated by the American Association of Blood Banks – a voluntary organization that accredits blood banks as a way of assuring high quality and providing continued education for blood bank professionals.^9,10

Blood donor recruitment

In developed countries, whether or not there is a national blood program, blood is collected from volunteer donors. The costs that are incurred in collection, testing, production and distribution of blood components are covered in a variety of ways depending on the method of financing healthcare in each country. In some countries, these costs are part of the national health service budget and the funds may be provided to hospitals to purchase blood from the national blood program or the Red Cross. In other countries, the funds may be provided directly to the national blood program or the Red Cross and the blood is then supplied without charge to the hospitals. In many parts of the world, especially in areas without a structured blood system and where individual hospitals must attempt to meet their own blood requirements, patients and their families may be required to obtain a certain number of donors or units of blood before procedures involving blood loss will be undertaken. This requirement may even lead to families paying individuals to donate blood on their behalf. The payment then creates the difficulties of a paid-donor system described earlier.

In developed countries, most people will require a blood transfusion at some time in their lives. The blood supply comes from a small group of dedicated donors. In the US, blood donors differ from the general population in that they are more likely to be male, aged 30–50, more highly educated, employed and Caucasian.¹¹ Although there have been some studies of the social psychology and motivation of blood donors,¹² the process is not well understood and is likely to vary for different ethnic or cultural groups or countries.¹² A recent developing concern is that with the increasingly stringent donor requirements resulting from the AIDS epidemic, a larger portion of the population is being excluded as potential donors. In addition, as the population in many developed countries ages, there is a decreasing portion of the population available for blood donation. In the US, only about a third of the population meets all the donor requirements.¹³

Plasma

A large number of therapeutic products such as albumin, intramuscular and intravenous immune globulin, and coagulation factor concentrates are prepared from plasma by using large-scale manufacturing processes. The plasma to serve as raw material may be obtained from individual units of whole blood or by plasmapheresis. Worldwide, the demand for these plasma derivatives exceeds that provided from plasma obtained from whole blood donations. Thus, a large amount of the plasma that serves as raw material for the production of derivatives is obtained by plasmapheresis. Plasmapheresis donation requires more time than whole blood donation, and because red cells are not removed from the donor, the donor can donate plasma more frequently than whole blood; in some countries, plasmapheresis donors are paid.

In the US, the plasmapheresis collection and plasma fractionation system is separate from the whole blood collection system. This plasma system is operated by large commercial companies that pay donors and produce plasma derivatives for profit. Thus, it differs in many ways from the whole blood collection system which relies on volunteer donors and is operated by non-profit organizations. In most other developed countries, the plasma system is operated as a not-for-profit system, often as part of the regular, whole blood collection system. Some countries operate their own plasma fractionation plant while others contract with plants operated in other countries. Plasma fractionation involves the processing of up to 10 000 liters of plasma, which may be pooled from as many as 50 000 donors. Thus, the potential for infectivity is substantial. Since the AIDS epidemic, the plasma fractionation industry has introduced pathogen inactivation systems and today most, if not all, plasma derivatives are free of transmission of most viral diseases. Presently many coagulation factor concentrates are manufactured using recombinant DNA technology and thus are free of disease transmission.

The AIDS epidemic has had a major impact on blood banking and transfusion medicine. Although blood bank professionals believe they acted properly, with reasonable speed, and with the public’s interest in mind to balance blood safety and blood availability, in many countries the public was not satisfied with this response. The plasma industry was subjected to even more severe criticism, particularly from the hemophilia community. Because plasma derivatives, including coagulation factor concentrates, are prepared from large pools of plasma containing plasma from many donors, a large proportion of these derivatives was contaminated with HIV and many hemophiliacs were infected. Although the plasma industry moved expeditiously to introduce pathogen inactivation steps into the manufacturing process, there was a widely held belief that these companies should have implemented these steps sooner. In addition, in some countries, criminal actions were taken successfully against leaders of the blood programs for failure to take certain actions that might have helped to mitigate the impact of the AIDS epidemic on transfusion recipients. As a result of the AIDS epidemic, there has been a substantial increase in the eligibility requirements for blood donors and increase in the number and specificity of questions about donor’s medical history and activities that might place them at risk of being infected with transfusion-transmitted diseases. In addition, the number of tests performed on donated blood has increased and there has also been a fundamental shift in the regulatory philosophy. In most developed countries, the expectation developed that blood donor screening, collection, processing and component production would be carried out much like a pharmaceutical manufacturing process.^5,10 In addition, the use of blood products also changed dramatically. Physicians became much more conservative in prescribing blood and more extensive use of guidelines and monitoring of transfusions has occurred.

Medical history

Selection of blood donors involves ensuring the safety of the donor and obtaining a blood component that is high in quality and has the least possible chance of transmitting disease. This is accomplished by using volunteer blood donors, questioning donors about their general health and medical history, carrying out a brief physical examination of each donor, and laboratory testing the donated blood. The questions used in each country will differ to reflect the kinds of disease exposure donors are most likely to encounter. The general principles will apply, however: questions intended to protect the donor from risks of blood donation and questions (primarily related to infectious diseases) intended to protect the recipient by identifying and excluding donors whose blood might be infectious.

Examples of questions in the medical history designed to protect the donor include whether the donor is under the care of a physician or has a history of cardiovascular or lung disease, seizures, present or recent pregnancy, recent donation of blood or plasma, recent major illness or surgery, unexplained weight loss, unusual bleeding, or is taking medications. Questions about medications help to identify any diseases or illnesses that might make blood donation a risk for the donor.

Most of the questions designed to protect the recipient deal with exposure to infectious diseases. Examples of these questions are the occurrence of or exposure to hepatitis or other liver disease, HIV (or symptoms of AIDS), Chagas disease or babesiosis; use of injected drugs; receipt of growth hormone, coagulation factor concentrates, blood transfusion, recent immunizations, tattoo, acupuncture, ear piercing, or an organ or tissue transplant; travel to areas endemic for malaria; presence of a major illness or surgery; or previous notice of a positive test for a transmissible disease. Examples of questions related to HIV risk behavior include whether the potential donor has had sex with anyone with AIDS, has given or received money or drugs for sex, (for males) has had sex with another male, (for females) has had sex with a male who has had sex with another male.

Physical and laboratory examination of the blood donor

The donor’s general appearance is assessed for any signs of illness or the influence of drugs or alcohol. The skin is examined for signs of intravenous drug abuse, lesions suggestive of Kaposi’s sarcoma, and local lesions that might make it difficult to decontaminate the skin and thus lead to contamination of the blood unit during venipuncture. Physical examination of the potential donor usually includes the temperature, pulse, blood pressure, weight and blood hemoglobin concentration. The specific requirements for these measures are established by the regulatory agency of each country.

Collection of whole blood

Blood is collected into plastic bags, each of which is sterile and can be used only once. Often combinations of bags are used so that whole blood can be separated into its components in a closed system, thus minimizing the chance of bacterial contamination while making storage of the components for days or weeks possible. The venipuncture site is an area free of skin lesions; it is scrubbed with a soap solution followed by an iodine solution. Because bacterial contamination of blood can be a serious or even fatal complication of transfusion,^14,15 it is important to minimize bacterial contamination by selecting a good venipuncture site and decontaminating it properly.

Special blood donations

Most blood is collected for placement in a ‘bank’ to provide for the general community and thus may be used by any patient. However, some blood donations are made intentionally to be used by a specific patient. Examples of these include autologous donation, directed donation and patient-specific donation. In some of these situations the usual regulations for blood donation may not apply.

Autologous blood donation

Autologous blood donation can be done in several ways: preoperative donation, acute normovolemic hemodilution, also known as perioperative hemodilution, intraoperative salvage, and/or postoperative salvage.

In the early 1990s, there was great excitement about the potential of autologous blood and it was estimated that in the US autologous blood could account for 20% of all blood used.²² This has not occurred because much of the autologous blood was collected from patients undergoing procedures with little likelihood of needing blood, surgeons became more skilled at minimizing blood loss, and anesthesiologists became more skilled at managing fluid administration and maintaining patients with lower hemoglobin levels. In 2004, only 3% of donation in the US was autologous.⁶

Preoperative donation. If an elective procedure is scheduled and there is a high likelihood of blood transfusion, the patient can donate blood in advance for his/her own use. Since the donor is actually a patient, they usually do not meet the regulatory requirements for normal blood donation. Thus, the blood is usually not suitable for use by someone else if it is not needed by the original donor/patient. Thus, it is important that autologous blood be collected only for procedures in which there is substantial likelihood that it will be used. Without this type of planning, there is a very high rate of wastage of autologous blood (estimated at 40.4% in the US in 2004).⁶ This amount of waste also means that the costs of autologous blood are quite high.²³

Although there are some contraindications for preoperative autologous blood donation such as bacteremia, symptomatic angina, recent seizures and symptomatic valvular heart lesions, the usual donor requirements do not apply and the final decision whether to withdraw blood from an autologous donor rests with the medical director of the blood bank. This decision may necessitate consultation between the donor’s/patient’s physician and the blood bank physician.

There are no age or weight restrictions for autologous donation. Pregnant women may donate, but donation is not recommended routinely because these patients rarely require transfusion. The autologous donor’s hemoglobin may be lower than that required for routine donors and autologous donors may donate several times within a few weeks prior to the planned surgery. However, usually it is only possible to obtain 2–4 units of blood before the hemoglobin falls to unacceptably low levels.

In most countries, autologous blood must be typed for ABO and D antigen, and at least the first unit must be tested for transmissible diseases. If any of the transmissible disease tests are positive, it may be necessary to label the unit(s) as biohazard in order to alert healthcare personnel to the hazard presented by the potentially infectious blood.

With the discovery of erythropoietin, there was great hope that it could be given to autologous blood donors to increase the number of units they could donate and substantially reduce the use of the general blood supply. Unfortunately this has not occurred because erythropoietin does not result in a meaningful increase in autologous blood units obtained from each patient.

Perioperative hemodilution (acute normovolemic hemodilution).²⁴ Perioperative hemodilution is carried out in the operating room usually after the patient has undergone general anesthesia. One to two units of whole blood are collected and replaced with an electrolyte solution at three times the volume of blood collected. The patient’s hematocrit is maintained at least at 30%. This procedure does not pose unusual risks to patients who are stable and undergoing elective surgery. If it is carried out prior to surgical procedures in which substantial expected blood loss is expected, the 2 units of freshly collected blood are kept in the operating room and can be transfused to the patient during surgery. Theoretical advantages of perioperative hemodilution, in addition to having the blood available, are that blood loss during surgery occurs at a lower hematocrit and thus there is less red cell loss, that surgery is carried out at lower hematocrit which improves blood viscosity and possibly provides better tissue oxygenation, and that the blood that is available for transfusion is fresh. Perioperative hemodilution must be carried out by a committed, knowledgeable anesthesia staff and it appears to have limited but definite value.

Intraoperative blood salvage. In elective, urgent or trauma surgery when substantial blood loss is expected, some of the shed blood can be recovered and returned to the patient. Several devices that combine suction, centrifugation and washing are available for this purpose. Because of the cost of operating these devices, intraoperative blood salvage is usually reserved for situations in which the blood loss is expected to exceed 1000 ml. The device suctions or aspirates blood from the operative site. The collected blood is centrifuged, and, in some cases, a wash solution is added. After processing, the blood is pumped out of the device into a plastic bag so it can be used for transfusion. Contraindications to intraoperative blood salvage are bacterial contamination of the operative site and surgery for malignancy. In both of these situations, transfusion of blood containing bacteria or malignant cells would be undesirable. Examples of situations in which intraoperative blood salvage is used most commonly are vascular surgery, cardiovascular surgery and some major orthopedics procedures.

Postoperative blood salvage. In some situations such as cardiovascular or orthopedic surgery, if there is extensive postoperative bleeding or draining from the surgical site, devices can be used to collect this drainage so that the shed blood can be used for transfusion. This use of postoperative blood salvage has not gained widespread acceptance because the volume of red cells that can be obtained is usually small; if substantial surgical site drainage is occurring, this often indicates a surgical problem that requires intervention. The shed blood usually contains activated coagulation factors, fibrin strands, cellular aggregates and other debris which make transfusion of this material undesirable.

Directed donor blood

Directed donors are friends or relatives who wish to give blood for a specific patient. Usually this is done because the patient hopes those donors will be ‘safer’ than regular blood donors. In some parts of the world, however, directed donation is a necessity because the general blood supply is not adequate. In the US, data do not indicate that directed donors have a lower incidence of transmissible disease markers,²⁵ and thus there is no factual rationale for these donations. Directed donors must meet all of the regulatory requirements for routine blood donation. Their blood becomes part of the community’s general blood supply if it is not used for the originally intended patient.

Therapeutic bleeding

Blood may be collected as part of the therapy for diseases such as polycythemia vera or hemochromatosis. This blood is not usually used for transfusion because the donors do not meet the FDA requirements. As the genetic basis for hemochromatosis has become known, efforts have begun to gain approval for the use of blood obtained from patients with hemochromatosis.^26,27 Limited experience suggests that a donor program could be effective, but it is not likely that blood from hemochromatosis patients would have a substantial impact on the nation’s blood supply.²⁸

Red blood cells

If whole blood is centrifuged and most of the platelets and plasma are removed, the resulting packed red cells or red cell concentrate is resuspended in a solution to optimize red cell preservation and allow storage of red cells for 42 days at 1–6°C. During the 42 days of storage, there is some loss of viability, adenosine triphosphate, membrane lipid and 2.3-DPG (causing increased affinity of hemoglobin for oxygen), reduced transmembrane transport of sodium and potassium, and accumulation of metabolites. Each unit of red cells has a volume of approximately 300 ml and contains about 200 ml of red cells. Red cells are used to provide oxygen-carrying capacity in anemic patients. The number of units given depends on the degree of anemia or blood loss.

Fresh frozen plasma

In the US, when the unit of whole blood is centrifuged, platelet-rich plasma results. The platelet-rich plasma is then centrifuged and the plasma and platelets are separated, resulting in a unit of plasma and a platelet concentrate. If this plasma is placed at −18°C or colder within 8 hours of collection it is called fresh frozen plasma. Fresh frozen plasma can be stored for up to 1 year at −18°C or colder. The unit of fresh frozen plasma has a volume of approximately 185 ml and contains all the constituents of citrated normal plasma such as the coagulation factors, the components of the complement and fibrinolytic systems, and the plasma proteins that maintain osmotic pressure and modulate immunity.

For transfusion, fresh frozen plasma is thawed in a 37°C water bath for approximately 30 minutes. Microwave ovens usually are not used to thaw fresh frozen plasma because they create hot spots that damage the plasma proteins. Thawed plasma should be transfused as soon as possible, but at the latest within 24 hours. If not used by then, it can be relabeled as thawed plasma and stored for an additional 4 days, although it will have reduced levels of factors V and VIII.

Plasma and source plasma

Plasma can also be removed from whole blood up to 24 hours after collection and stored at −18°C or less and stored for up to 1 year. This 24 hour frozen plasma has reduced levels of factor VIII. Source plasma is collected by plasmapheresis and is intended to serve as the raw material for further manufacture into blood derivatives.

Cryoprecipitate

When previously frozen plasma is thawed at 1–6°C, an insoluble material called cryoprecipitate remains after the liquid plasma is removed. Each bag of cryoprecipitate contains about 100 units of factor VIII and 200 mg of fibrinogen and has a volume of about 10 ml. It can be stored for up to 1 year at −18°C or lower. Cryoprecipitate is thawed in a 37°C water bath, and cryoprecipitate from multiple bags is usually pooled into a single container that is dispensed by the blood bank. Cryoprecipitate is usually given in the same ABO type as the recipient. If there is a shortage, small amounts of ABO-incompatible cryoprecipitate can be given. There is usually little risk of hemolysis from small volumes of ABO-incompatible plasma because the volume of plasma from any individual donor who might have a high-titer antibody is only 10 ml. Because cryoprecipitate contains few red cells, it can be given without regard to Rh type.

Cryoprecipitate was developed originally as a source of factor VIII and was the first concentrated form of this coagulation factor available to treat hemophilia. With the development of coagulation factor concentrates that have undergone viral inactivation, the major use of cryoprecipitate currently is as a source of fibrinogen or as fibrin glue.²⁹

Whole blood-derived platelet concentrates – platelet-rich plasma method

Platelets can be produced from units of whole blood or by plateletpheresis. In the US, when platelets are prepared from whole blood, the unit of whole blood is maintained at room temperature and centrifuged, and the platelet-rich plasma is passed into a satellite bag. The platelet-rich plasma is centrifuged again, and the platelet-poor plasma is passed into another satellite bag leaving the platelet concentrate which has a volume of proximately 50 ml. At least 75% of random donor-platelet concentrates contain at least 5.5 × 10¹⁰ platelets. Four to six units of random-donor platelets are pooled to provide a therapeutic dose for transfusion. These whole blood-derived platelet concentrates may then be stored for up to 5 days at room temperature (20–24°C). The variables known to be important in platelet preservation are: temperature, method of agitation, volume of suspending plasma and type of storage container. At the end of the storage period, the intravascular recovery and half-life of the stored platelets are approximately 51% and 3.1 days.³⁰

Whole blood-derived platelet concentrates – buffy coat method

In some countries, the whole blood is centrifuged and the buffy coat containing leukocytes and platelets is removed.³¹ Buffy coats from several units are pooled, the pooled buffy coats are centrifuged, and the platelets are separated from the leukocytes to provide a platelet concentrate. This method provides a therapeutic dose of platelets and no further pooling is necessary. It is thought that this method of preparation provides better platelet function,³¹ although it has not been adopted in the US.

Platelet concentrates

Plateletpheresis usually takes about 90 minutes during which about 4000–5000 liters of the donor’s blood are processed through the blood cell separator. These platelet concentrates have a volume of about 200 ml and contain about 3.5 × 10¹¹ platelets and less than 0.5 ml of red cells. This provides a therapeutic dose of platelets for transfusion. Plateletpheresis has been used increasingly so that in the US about 80% of platelets are produced by plateletpheresis,⁶ but plateletpheresis is much less common in many other countries.

Granulocyte concentrates

Because of the small number of circulating granulocytes, it is not practical to prepare granulocyte concentrates from whole blood donations. Instead, leukapheresis is used to process 6.5–8.0 ml of donor blood during about three hours³² and obtain a granulocyte concentrate. Hydroxyethyl starch is added to the blood cell separator flow system to sediment the red cells and improve the separation of granulocytes from other blood components. To increase the donor’s peripheral blood granulocyte count, and thus increase the yield of granulocytes, dexamethasone and recently, granulocyte colony-stimulating factor (G-CSF) has been administered to granulocyte donors.³³

Mononuclear cell concentrates

Mononuclear cell collection is also done by cytapheresis. This produces a component containing approximately 1 × 10¹⁰ mononuclear cells, which are a mixture of lymphocytes and monocytes. These mononuclear cell concentrates may be used for direct transfusion such as in adoptive immunotherapy to prevent relapse of CML following stem cell transplantation or as the starting material for further processing as part of gene therapy or adoptive immunotherapy.

Plasma

Plasmapheresis can be done using sets of multiple attached bags, but this is time-consuming, cumbersome and involves disconnecting the blood bags from the donor to centrifuge and separate the plasma from the red cells. This creates the chance of returning the blood to the wrong donor. Semi-automated instruments are used that require less operator involvement than the bag systems, while producing up to 750 ml of plasma in about 30 minutes depending on the size of the donor. Because few red cells are removed, the procedure can be repeated frequently so that a donor could provide large amounts of plasma.

Peripheral blood stem cells

Hematopoietic stem cells present in the peripheral blood that are capable of providing complete hematopoietic reconstitution in humans stimulated the development of methods to collect peripheral blood stem cells by cytapheresis.^33,34 The number of peripheral blood stem cells (PBSCs) circulating under usual conditions is low but following chemotherapy there is a rebound and a large number of PBSCs can be obtained by apheresis. G-CSF is also given to patients or normal donors to increase the number of circulating PBSCs and provide an adequate dose of cells for successful reconstitution of hematopoiesis.^35,36 Usually approximately 1 × 10¹⁰ mononuclear cells and 2–6 × 10⁷ CD34⁺ cells are obtained after processing up to 15 l of the donor’s blood during 4–5 hours. The concentrate has a volume of about 200 ml.

Selection of apheresis donors

The criteria and requirements for donors of whole blood apply to the selection of donors for apheresis;³⁷ however, there are some additional requirements. These may vary in different countries, but they generally define the volume of blood that can be extracorporeal during apheresis, the volume of red cells or plasma that can be removed in a given time, the frequency of donation, and any laboratory tests in addition to those performed for whole blood donation. The laboratory testing of donors for transmissible diseases is the same as that for whole blood donation. Thus, the likelihood of disease transmission from apheresis components is the same as that from components prepared from whole blood.

Reactions in apheresis donors

In general, the types of adverse reactions that occur following cytapheresis are similar to those following whole blood donation. However, some side-effects or reactions unique to cytapheresis occur.³² These include paresthesias due to the infusion of the citrate used to anticoagulate the donor’s blood while it is in the cell separator; myalgia, arthralgia, headache, or flu-like symptoms due to G-CSF in granulocyte donors;^32,37 or headache and/or hypertension from blood volume expansion due to the sedimenting agent hydroxyethyl starch used in the cell separator to improve the granulocyte yield.