Has a shelf-life of 35 days. 70 ml citrate preservative solution is added to 420 ml blood. All other blood products are derived from whole blood. After 3 days, the platelets will not function and after 3 weeks the levels of 2,3-diphosphoglycerate (2,3-DPG) diminish. There are normal concentrations of albumin and clotting factors, except factors V and VIII, which are reduced to 20% of normal. Heparinised whole blood lasts for two days and has been used in paediatric cardiac surgery.
Each 250 ml bag has a haematocrit of 0.6. There are no platelets, and 2,3-DPG levels remain normal for up to 14 days. Packed cells may be stored for 35 days with SAGM (saline, adenine, glucose, mannitol) or for up to 42 days with A-CPD (adenine, citrate, phosphate, dextrose).
Platelets used for transfusion can come from two sources: platelet concentrates derived from a unit of whole blood, called random donor platelet concentrates (RDP); or apheresis platelets obtained from a single donor by plateletpheresis. Each random donor platelet contains >50x109 platelets in approximately 50 ml of plasma and is pooled in the required dose. A single donor platelet (SDP) obtained by apheresis contains the equivalent number of platelets in 6-8 units of RDP and contains approximately 200 - 300ml plasma.
Both RDP and SDP can be stored up to five days at 20-24°C (room temperature). They must be continually agitated to prevent clumping. Storage is limited to five days due to the risk of bacterial contamination.
Platelets are labeled with ABO and Rh type. ABO identical or compatible platelets are preferred. However, in adults ABO incompatible platelets may be uses because the amount of plasma is rarely of clinical concern. Crossmatching is not required because platelets contain only small numbers of contaminating red cells (2-5 ml). However this number of red cells is capable of causing immunization to the D antigen. Thus Rh compatibility is required in Rh negative children and women of child bearing age to prevent the formation of anti-D and potentially hemolytic disease of the newborn.
The recommended dose of RDP is 1unit/10kg body weight. The expected increment in platelet count is 5-10,000/ul per unit of platelet transfused. The smaller the patient the larger the relative dose. Thus an infant or small child may increment 25-50,000/ul per unit of RDP. For adults, 1 SDP is a therapeutic dose. For children, an SDP may contain an excessive dose of platelets. In these situations the SDP may be split or aliquoted. The expected platelet count increment from an SDP in an adult is 25 - 50,000/ul.
Platelet transfusions are indicated to treat or prevent bleeding in patients with clinically significant deficiencies in platelet number or function. The indication for prophylactic platelets to prevent bleeding in patients with severe thrombocytopenia is an evolving area. Recent studies and several years of experience have shown that the previously recommended "trigger" of 20,000/ul is not required for many patients since the risk of significant spontaneous bleeding in an otherwise stable patient does not occur until the platelet count is <10,000/ul. Patients with fever, sepsis, coagulopathy, or anatomic bleeding (i.e. severe mucocytis) may require higher platelet levels.
In the bleeding patient or a patient who is undergoing an invasive procedure platelet transfusions are recommended for counts of <50,000/ul. Patients with a coagulopathy in addition to thrombocytopenia may require transfusion at higher levels.
Prophylaxis: <10,000/ul (stable patient)
Bleeding patient: <50,000/ul
Invasive procedure: <50,000/ul
Deficiencies in platelet function may be observed in the absence of thrombocytopenia. While some causes of platelet dysfunction such as aspirin induced can be treated with platelet transfusion, others such as ureamic bleeding are not appropriately treated with platelet transfusion. Platelet transfusions are accompanied by fever-chill reactions in 1% of all transfusions but in as many as 30% of transfusions in multitransfused patients. These reactions occur due to white cells contaminating the platelet component or to cytokines released by the white cells into the platelet supernatant during storage. The reactions can be mitigated by using leukoreduced platelet components and/or using platelets with reduced storage time i.e. 3 days. Allergic reactions occur in 1% of platelet transfusions and are generally mild and easily treated with antihistamines. Rare reactions to platelets include: septic reactions due to bacterial contamination, graft vs. host disease, and ARDS (transfusion related acute lung injury).
The risk of viral transmission is the same as that for any unit of blood. However, since RDP are pooled they typically contain 6-8 donor exposures Vs 1 for an SDP. Fortunately the risk of viral transmission has become so small that the difference in donor exposures between a pool and an SDP is of little concern in the patients who most frequently require platelet transfusions; stem cell transplant recipients and older patients undergoing cardiac surgery.
Fresh frozen plasma
This is produced from plasma from a single donation. Each 150 ml bag contains all clotting factors, albumin and gamma-globulin. FFP must be used immediately after thawing and must be ABO compatible. Plasma frozen to -20°C. The usual starting dose is 10-15 ml/kg (equivalent to four packs of FFP for a 70kg person), which raises the coagulation levels 12-15%. FFP for children born after 1995 is derived from unpaid US donors.
This is precipitated from FFP when slowly thawed. Contains high levels of factor VIII, fibrinogen and von Willebrand factor. Cryoprecipitate is prepared from a single donation. Each unit contains a volume of 20-40 ml. It is stored at –30oC for up to 12 months and is thawed to 37oC immediately before use. The concentration of fibrinogen is >140mg/unit and factor VIIIc >70 IU/unit. ABO compatible units should be used, and treatment considered if the plasma fibrinogen is <0.8 g/litre. Ten units of cryoprecipitate should increase fibrinogen level by 1 g/litre.
Guidelines for the use of fresh-frozen plasma, cryoprecipitate and cryosupernatant