Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Blood Transfusion
Principles of Blood Transfusion
The ability to safely transfuse blood and blood products has revolutionised outcomes from major trauma and from complex surgery involving heavy blood loss, such as arterial reconstruction, open-heart surgery and organ transplantation. For replacing blood loss, stored blood restores the circulation, increases oxygen carrying capacity and helps prevents hypoxia. Modern blood transfusion is very safe but deaths and major morbidity still occur. Potential hazards include clerical errors leading to incompatible transfusion, transfusion reactions and transmission of infection.
Over the last two decades, indications for blood transfusion have been carefully scrutinised. As a result, restrictive blood transfusion strategies have been adopted and used in conjunction with clinical assessment. Patients requiring blood transfusion must be informed about the indications, risks, benefits and any alternatives and given the option to refuse (see the National Institute for Health and Care Excellence [NICE] Blood Transfusion guidance: https://www.nice.org.uk/guidance/ng24 ). Before transfusion, valid consent should be obtained and documented in the patient’s notes (see: https:// www.gov.uk/government/publications/patient-consent-for-blood-transfusion ). Details about any blood transfusion given should be included in a patient’s discharge summary to their GP.
Reducing the Need for Bank Blood Transfusion
Surgical blood use in the United Kingdom has fallen by more than 20% since 2000 in line with the increasing evidence for the benefits of restrictive transfusion policies. However, deaths and serious reactions still occur from incompatible transfusions, particularly when blood products are administered under general anaesthesia. Serious infections, such as hepatitis, malaria, human immunodeficiency virus (HIV) and variant Creutzfeldt–Jakob disease (vCJD) can be transmitted despite careful screening of donors and donations. The risk increases proportionately to the number of units transfused and can be reduced by critical scrutiny of the indications for transfusion.
Recognition and Treatment of Preoperative Anaemia
Anaemia is an independent factor predicting adverse outcomes from surgery. Patients who are anaemic preoperatively (haemoglobin [Hb] <130 g/L in adult males and Hb <120 g/L in adult females) are more likely to be transfused, and anaemic patients are at increased risk of mortality and major morbidity in proportion to the severity of the anaemia.
Iron deficiency is the most common type of anaemia found in preoperative screening. For men and postmenopausal women, potential gastrointestinal (GI) causes of bleeding must be investigated. Once identified, iron deficiency should generally be treated with oral iron ( https://www.nice.org.uk/guidance/ng24 ). If time does not permit or if patients are unable to tolerate oral iron, parenteral iron should be offered. Other causes of anaemia (vitamin B 12 and/or folate deficiency, renal anaemia or an underlying haematological condition) should be identified and addressed.
Erythropoietin-stimulating agent is not recommended before surgery except for patients with renal anaemia on dialysis or where avoiding transfusion is highly desirable (e.g., in patients refusing blood or those with complex antibodies and complex cross-match requirements).
Patients at Risk of Bleeding
Patients at risk of bleeding include those with thrombocytopenia, coagulopathies and those on anticoagulation and antiplatelet therapy. A management plan should be agreed in advance of surgery, including timely discontinuation of medications. In surgical emergencies, anticoagulation may need urgent reversal. Intravenous vitamin K reverses the anticoagulant effects of warfarin in 6 to 8 hours; prothrombin complex concentrate acts immediately. Heparin is reversed with protamine sulphate. Antiplatelet agents and newer anticoagulants (direct oral thrombin and anti-Xa inhibitors) can be reversed in some cases (i.e., idarucizumab is an antidote for dabigatran) and requires haematology guidance.
Minimising Blood Loss During Surgery
In addition to scrupulous haemostasis with diathermy, clips, ties or the use of other products, such as tissue sealants during surgical procedures, additional measures such as intraoperative cell salvage (IOCS) can be used where appropriate.
Intraoperative Cell Salvage
IOCS involves collecting blood spilled at operation by suction, then washing it in physiological solution and concentrating it. This blood, with a packed cell volume of 50%, can then be reinfused. It is recommended for patients with anticipated blood loss >20% of blood volume, those with risk factors for bleeding, in major haemorrhage, and for patients with rare blood groups. Some patients who do not accept donor blood are prepared to accept and consent to IOCS (including some Jehovah’s Witnesses). The technique remains controversial in malignant disease.
Antifibrinolytic Agents
Tranexamic acid is recommended by NICE for operations with an expected blood loss of >500 mL. It is also recommended in major haemorrhage because of trauma or GI haemorrhage.
Avoiding Unnecessary Transfusion After Surgery
Postsurgery blood transfusion can be minimised by accepting restrictive transfusion triggers and by adhering to the single unit transfusion policy described later. Prescription of oral or parenteral iron can minimise use of bank blood and contribute to the patient’s recovery.
Postoperative cell savers enable blood lost in the postoperative period to be collected via a filtered wound drain and transfused via another filter. This is suitable for procedures with an anticipated substantial ‘clean’ postoperative blood loss, such as total knee replacement.
Laboratory Aspects of Blood Transfusion
When transfusion is deemed appropriate, the correct component(s) must be selected according to clinical indications. The types of transfusion components and the general indications for their use are summarised in Table 9.1 .
TABLE 9.1
Types of Blood Component Transfusions and Indications for Their Use a
| Component | Indication | Volume | Adult Dose | Storage Temperature | Shelf Life | Comments |
|---|---|---|---|---|---|---|
| Red cells | Substantial haemorrhage and severe anaemia | 220–240 mL | One unit (which increases Hb concentration by 10 g/L) | 2°C–6°C | 35 days from donation | Whole blood is centrifuged to separate red cells, platelets and plasma. Red cells can be washed or irradiated and suspended in preservative solution. |
| Fresh frozen plasma (FFP) | Replacing clotting factors during major haemorrhage | 274 mL | 10–15 mL/kg (four units) | < −25°C | Frozen: 36 months; thawed at 4°C: 24 hours to 5 days; room temperature: 4 hours | Prepared from fresh whole blood or donations by apheresis b and then frozen. FFP contains near normal amounts of clotting factors. Also used to treat TTP and acute DIC |
| Platelet concentrate | Treatment or prevention of bleeding for patients with thrombocytopenia or platelet dysfunction defects | 200–300 mL | One unit (which increases platelet counts by 10 × 10 9 /L per unit transfused) | 20°C–24°C | 2–7 days (if bacterially screened) | Mean platelet count is 165–500 × 10 9 /L. Platelet counts should be >50 × 10 9 /L for most surgical procedure and >100 × 10 9 /L for neurosurgery, back or eye surgery and multiple trauma. Platelets are prepared from pooled buffy coats (four donors per pack) or from apheresis donations |
| Cryoprecipitate | Source of fibrinogen in major haemorrhage and DIC | 43 mL | Available as pools of 5 units (total volume: 189 mL). Adult dose is 2 pools | < −25°C | Frozen: 36 months. Use within 4 hours of thawing | Cryoprecipitate is made by thawing FFP at 4°C, producing a cryoglobulin rich in fibrinogen, Factor VIII and von Willebrand factor |
DIC, Disseminating intravascular coagulation; TTP, thrombotic thrombocytopenic purpura.
a National and hospital-based guidelines are produced giving indications for red cell, platelet and fresh frozen plasma transfusion. For regular updates and for information about granulocytes and other plasma derivatives, such as human albumin solution, clotting factor concentrates and immunoglobulin solutions, please visit https:// www.transfusionguidelines.org/red-book .
b Apheresis = process which involves removal of whole blood from the donor; blood components are separated by centrifuge, the desired constituent (i.e., plasma) is withdrawn and the remaining components retransfused into the donor.
The patient’s history, including current/previous diseases and treatment, can give important information to help select suitable blood and blood components (e.g., irradiated platelets must be used for patients at risk of graft-versus-host disease).
You're Reading a Preview
Become a Clinical Tree membership for Full access and enjoy Unlimited articles
If you are a member. Log in here