Summary points
* Autologous transfusion reduces the need for allogeneic transfusion and is most widely used in elective surgery
* Autologous transfusion is one of several techniques used to reduce the need for allogeneic transfusion
* The three main techniques are predeposit transfusion, intraoperative haemodilution, and intraoperative and postoperative salvage
* Evidence from clinical trials shows that autologous transfusion is more cost effective than allogeneic transfusion and that clinical outcomes are improved
Predeposit autologous transfusion entails repeated preoperative phlebotomy (fig 2). Blood collection begins three to five weeks before elective surgery, depending on the number of units required, usually 2-4 units (about 1-2 litres). The last donation takes place at least 48-72 hours before surgery to allow for re-equilibration of the blood volume. On each occasion, about half a litre of the patient's own blood is taken and put into sterile plastic bags. Anticoagulation is maintained with citrated glucose solution, and the blood is stored until the time of surgery.Advantages
Predeposit autologous transfusion virtually eliminates the risks of viral transmission and immunologically mediated haemolytic, febrile, or allergic reactions. These adverse effects range in frequency from 1 in 1 000 000 (HIV) to as high as 5% (febrile reactions). In addition, it may decrease the risk of postoperative infection and recurrence of cancer because immunomodulation as a result of transfusion is avoided.2–4 Immunomodulation refers to decreases in cellular immune function that have been documented after allogeneic, but not autologous, transfusions.7
Disadvantages
Up to half of the blood that is collected may be discarded because the amount drawn off needs to exceed the median routinely needed to avoid additional allogeneic transfusions. Leftover blood can rarely be used for other patients because most autologous donors do not meet the stringent health requirements for allogeneic blood donation. This wastage of blood and the costs of administering autologous programmes result in collection costs that are higher than those for allogeneic transfusion. Volume overload, bacterial contamination, and ABO haemolytic reactions to the transfusion resulting from administrative or clerical errors are further risks.
Suitability of patients
Predeposit autologous donation is practical only for elective surgery. Patients must be willing and able to travel to a donation centre before their operation, which can be inconvenient and stressful and may decrease their productivity at work. Because preoperative donation results in perioperative anaemia (which may not be completely resolved before surgery) blood volume, venous access, packed cell volume, and haemodynamic stability are important determinants of who is an appropriate candidate for the procedure. Children who weigh less than 30-40 kg are usually not suitable, but adult patients are deferred from donation only if they have severe haemodynamic problems, active systemic infections, or a history of serious reactions to donation (such as seizure). Patients with diarrhoeal illnesses in the days or weeks before donation should not donate as they may be at increased risk of bacterial contamination of their donated blood. Although autologous donors have a higher incidence of reactions such as fainting or dizziness than voluntary donors (presumably because they are inexperienced donors and not as young and fit), their reactions are seldom severe.
Intraoperative acute normovolaemic haemodilution
Acute normovolaemic haemodilution (“haemodilution”) is a type of autologous donation that is performed preoperatively in the operating theatre or anaesthetic area. It is usually restricted to patients in whom substantial blood loss is predicted (>1 litre or 20% of blood volume). Whole blood (1.0-1.5 litres) is removed, and simultaneously intravascular volume is replaced with crystalloid or colloid, or both, to maintain blood volume. The anticoagulated blood is then reinfused in the operating theatre during or shortly after surgical blood loss has stopped. The blood sparing benefit of haemodilution is the result of the reduced red cell mass lost during surgical bleeding.
Advantages
Haemodilution provides the advantages of predeposit autologous donation and some additional benefits. It may be used before any type of surgical procedure, and systemic infection does not preclude its use. The patient is under anaesthesia during the procedure, which reduces stress, and the anaesthetist can ensure expert monitoring of blood circulation. Blood is stored at room temperature for a short time, so deterioration of clotting factors and cells is minimal. Additional advantages include a lower cost than for predeposit transfusion (because testing and cross matching are not usually required) and minimal wastage, as most or all blood is reinfused. Blood is maintained at the point of care, incurring little or no administrative expense, and the risk of ABO incompatibility because of administrative or clerical error is further minimised.
Disadvantages
The circulating red cell mass is lowered appreciably and acutely. If colloid is used for volume replacement the risk of allergic reactions or haemostatic abnormalities increases. Other disadvantages are the additional expense of, and inconvenience to, the anaesthetist who performs the procedure. The procedure may require additional training and experience on the anaesthetist's part. No large studies have investigated morbidity or mortality that may occur with acute anaemia, so the general belief that haemodilution is safe is largely anecdotal at this time.
Suitability of patients
Elective operations with typical blood losses of 1-2 litres are particularly suitable for haemodilution (for example, replacement of cardiac valves, revision of hip arthroplasty, or spinal reconstruction). The major limiting factor in choosing candidates for haemodilution is the patient's ability to tolerate a low volume of red blood cells. Patients with severe anaemia are usually poor candidates.
Salvage autologous transfusion
Intraoperative red blood cell salvage entails the collection and reinfusion of blood lost during surgery. Shed blood is aspirated from the operative field into a specially designed centrifuge. Citrate or heparin anticoagulant is added, and the contents are filtered to remove clots and debris. Centrifuging concentrates the salvaged red cells, and saline washing may be used. This concentrate is then reinfused. Devices used can vary from simple, inexpensive, sterile bottles filled with anticoagulant to expensive, sophisticated, high speed cell washing devices. Postoperative salvage refers to the process of recovering blood from wound drains and reinfusing the collected fluid with or without washing.
:victory:advantage
Salvage is considered a safe and efficacious alternative to allogeneic red cell transfusion, but fewer data are available about clinical outcomes than for predeposit autologous donation or haemodilution.1 These techniques offer advantages similar to those of haemodilution but do not require infusions of crystalloid or colloid to preserve blood volume. Many litres of blood can be salvaged intraoperatively during extensive bleeding, far more than with other autologous techniques.
Disadvantages
Although the oxygen transport properties and survival of red cells are similar to that of allogeneic blood, salvaged blood is not haemostatically intact compared with blood derived by haemodilution. Coagulation in the wound leads to consumption of coagulation factors and platelets. Salvaged blood that is not washed contains raised concentrations of various tissue materials. Uncommon complications of extensive intraoperative salvage include disturbances to pH and electrolytes, systemic dissemination of non-sterile material, infectious agents or malignant cells, air or fluid embolism, and dilutional coagulopathy. A “salvaged blood syndrome” has been described, which entails multiorgan failure and consumption coagulopathy.8
Suitability of patients
Intraoperative salvage is used extensively in cardiac surgery, trauma surgery, and liver transplantation. Contraindications to its use are bacterial infection or malignant cells in the operative field, and use of microfibrillar collagen or other foreign material at the operative site. Salvage can be one of the most expensive autologous techniques because costly capital equipment and disposables are used, and it is usually restricted to procedures resulting in substantial blood loss (>1-2 litres). |
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发表于 2008-10-30 10:48:27
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