The components of whole blood are prepared by differential centrifugation of blood collected from volunteer donors.
■ Blood components, such as red cell and platelet concentrates, fresh frozen plasma (FFP) and cryoprecipitate, are prepared from single donors.
■ Blood components such as coagulation factor concentrates, albumin and immunoglobulin are prepared using plasma from many donors as the starting material.
Whole blood is rarely used, even for acute blood loss. Use of the required component is a more effective use of a scarce resource.
Red cell concentrates the plasma is removed from whole blood and replaced with an additive solution. Storage is at 4°C with a shelf-life of 35 days and transfusion should be completed within 4 hours of removal from cold storage. Red cell concentrates are used for acute bleeds in com-bination with crystalloid or colloid and correction of anaemia. Transfusion of red cells in addition to colloid is usually only necessary when >30% (>1500 mL in an adult) of circulating volume has been lost (p. 576). This degree of blood loss is manifest by reduced systolic and diastolic blood pressure, pulse rate >120/min, slow capillary refill and respiratory rate >20/ min. The patient will be pale and may be anxious and aggressive. Transfusion may be required for lesser degrees of blood loss that are superimposed on a pre-existing anaemia or reduced cardiorespiratory reserve capacity. Trans-fusion of red cells is rarely necessary for correction of chronic anaemia (where the underlying cause should be treated) unless the anaemia is severe and life-threatening.
Platelet concentrates are stored at +20°-24°C. Cold storage causes irreversible platelet aggregation. Platelets are used to treat or prevent bleed-ing in patients with severe thrombocytopenia. They are not used in stable chronic thrombocytopenia without bleeding. For platelet transfusion, the ABO and RhD group of the patient must be known and the same bedside checks and monitoring procedures as for red cell transfusion must be used. Usually 1 unit (250 mL of plasma containing >40 X 109/L platelets) is given, and the platelet count should rise by >20 X 109/L.
Fresh frozen plasma is separated from blood cells and frozen for storage. It contains all the coagulation factors and is used in acquired coagulation factor deficiencies.
Cryoprecipitate is the supernatant obtained after thawing of FFP at 4°C. It contains factor VIII : C, von Willebrand factor (vWF) and fibrinogen and is used in DIC where the fibrinogen level is very low (<1.0 g/L).
Factor VIIIandIX concentrates are used for the treatment of haemophilia and von Willebrand disease where recombinant factor concentrates are unavailable.
Albumin (4.5% and 20%) are given to patients with acute severe hypoalbuminaemia and to patients with liver disease and nephrotic syndrome (20% solution) who are fluid overloaded and resistant to diuretics.
Immunoglobulins are used in patients with hypogammaglobulinaemia to prevent infection and in patients with idiopathic thrombocytopenic purpura. Specific immunoglobulin, e.g. anti-hepatitis B, is used after exposure of a non-immune patient to infections.
Table 5.14 The ABO system: antigens and antibodies
Red cell antigen
Antibody in patient's plasma
No antibodies to A or B
No A or B
Anti A and anti-B
Biood groups O and A are the most common in the UK.
The blood groups are determined by antigens on the surface of red cells. The ABO and rhesus (Rh) systems are the two major blood groups. In the ABO groups individuals produce antibodies against the antigen that are not present on their own red cells (Table 5.14). If red cells carrying A or B antigens are transfused to someone who has antibodies to these then a severe immune reaction will occur leading to shock and DIC (p. 235) which may be fatal within minutes to hours. Patients with blood group AB can receive blood of any other ABO group and are known as universal recipients. Most of the population carry RhD antigens (Rh +ve) on their red cells and they can receive any RhD type blood. RhD -ve patients should receive RhD -ve blood. Expo-sure to RhD +ve blood through transfusion or pregnancy will lead to develop-ment of anti-D.
Procedure for blood transfusion
Compatibility testing is performed by the transfusion Service in order to select donor blood of the correct ABO and Rh group for the recipient and to screen the patient's serum or plasma for antibodies against other red cell antigens (such as Kell and Duffy) that may cause a transfusion reaction. After a massive bleed when immediate transfusion is necessary, O RhD -ve blood can be given without any transfusion investigations being undertaken. It should need to be used only on rare occasions.
Many hospitals have guidelines for the ordering of blood for elective surgery. Operations in which blood is required only occasionally can be clas-sified as ‘group and save', in order to conserve blood usage. In this case ABO and Rh testing is performed along with the antibody screen. Should blood unexpectedly be required during the course of the procedure, compatible units can be released within a matter of minutes after an immediate spin cross-match, whereby the patient's serum or plasma is incubated with the donor red cells to confirm compatibility.
|Table 5.15 Care of the patient receiving a blood transfusion or blood products|
|1 Taking the blood sample for cross-matching|
Identity patient positively by asking their surname, forename, date of birth Coníirm ID details on hospital wrist band match those on transtusion request torm
Label sample tube atter blood has been added Label sample tube with patient identiíication (tull name, date of birth, hospital number), patient location, date of sample and signature of person taking blood
|2 Procedure for patient identification before transfusion|
Check the blood bag is not leaking or wet and has a compatibility label attached
Check patient identity (tull name, sex, date of birth, hospital number) matches that on the blood transtusion request torm and compatibility label attached to the blood pack. This is now usually done by a handheld computer reading a barcode on the patient’s wristband and the compatibility label and ensuring a match.
Check intravenous fluid prescription chart
|3 Blood checks|
|Check expiry date of the blood on compatibility label and blood bag
Check blood group and blood pack donation number on blood transfusion
request form, blood pack and compatibility label
Record the blood pack donation number on intravenous fluid prescription chart
Date, time and signature on blood transfusion request form, compatibility label, intravenous fluid prescription chart
Blood transfusion is a potentially hazardous procedure, which should only be undertaken when the benefits outweigh the risks. Stringent procedures need to be followed to ensure that the correct blood is given to the correct patient and that any adverse reactions are dealt with promptly and efficiently (Table 5.15). The temperature, pulse rate and blood pressure should be recorded before the start of each unit, 15 minutes after the start and at hourly intervals during the transfusion. A temperature rise of 1 °C or greater above baseline may indicate an acute haemolytic transfusion reaction due to blood group incompatibility and is an indication to stop the transfusion.
Complications of transfusing red blood cells
■ ABO incompatibility is the most serious complication. It usually results from simple clerical errors, leading to the incorrect labelling and identi-fication of the correct patient receiving the correct blood at the correct time. Within minutes of starting the transfusion there is pyrexia, rigors, dyspnoea, hypotension, loin and back pain. Intravascular haemolysis leads to dark urine. The transfusion must be stopped and the donor units returned to the blood transfusion laboratory for testing with a new blood sample from the patient. Emergency treatment may be needed to main-tain the blood pressure (p. 578). Autoimmune haemolysis may develop about a week after transfusion in patients alloimmunized by previous transfusions in whom the antibody level is too low to be detected during compatibility testing.
■ Febrile reactions are usually the result of anti-leucocyte antibodies in the recipient acting against transfused leucocytes, leading to the release of pyrogens. These reactions are less common since the introduction of leucocyte-depleted blood.
■ Anaphylactic reactions are seen in patients lacking IgA but who produce anti-IgA that reacts with IgA in the transfused blood. This is a medical emergency (p. 576). Urticarial reactions are treated by slowing of the infusion and giving intravenous antihistamines, e.g. chlorphenamine (chlorpheniramine) 10 mg i.v.
■ Transmission of infection has decreased now that donated blood is tested for hepatitis B surface antigen and antibodies to hepatitis C, HIV-1 (human immunodeficiency virus) and HTLV-1 (human T-cell lymphotropic virus). Cytomegalovirus (CMV)-seronegative blood is given to immunosup-pressed patients who are susceptible to acquiring CMV infection.
■ Heart failure may occur, particularly in elderly people and those having large transfusions.
■ Complications of massive transfusion (>10 units within 24 hours) include hypocalcaemia, hyperkalaemia and hypothermia. Bleeding may occur as a result of depletion of platelets and clotting factors in stored blood.
■ Post-transfusion purpura is rare. Antibodies develop against the human platelet antigen 1a leading to immune destruction of the patient's own platelets and thrombocytopenia 2-12 days after a blood transfusion.
Concerns about the safety of blood transfusion have led to increased interest in strategies for avoiding or reducing the use of donor blood. These include artificial haemoglobin solutions and autologous blood transfusion. The latter is more popular in developing countries and involves collection of blood from the donor/patient either pre-operatively or by intraoperative blood salvage.
1. Ethics and communication
2. Infectious diseases
3. Gastroenterology and nutrition
4. Liver, biliary tract and pancreatic disease
Liver, biliary tract and pancreatic disease
LIVER BIOCHEMISTRY AND LIVER FUNCTION TESTS
SYMPTOMS AND SIGNS OF LIVER DISEASE
NON - ALCOHOLIC FATTY LIVER DISEASE (NAFLD)
COMPLICATIONS AND EFFECTS OF CIRRHOSIS
TYPES OF CHRONIC LIVER DISEASE AND CIRRHOSIS
PRIMARY SCLEROSING CHOLANGITIS
BUDD - CHIARI SYNDROME
LIVER DISEASE IN PREGNANCY
CARCINOMA OF THE PANCREAS
NEUROENDOCRINE TUMOURS OF THE PANCREAS
5. Haematological disease
Assessment and treatment of suspected neutropenic sepsis
INHERITED HAEMOLYTIC ANAEMIAS
ACQUIRED HAEMOLYTIC ANAEMIA
THE WHITE CELL
HAEMOSTASIS AND THROMBOSIS
6. Malignant disease
COMMON INVESTIGATIONS IN MUSCULOSKELETAL DISEASE
COMMON REGIONAL MUSCULOSKELETAL PROBLEMS
THE SERONEGATIVE SPONDYLOARTHROPATHIES
Clinical features, Investigations
INFECTION OF JOINTS AND BONES
AUTOIMMUNE RHEUMATIC DISEASES
SYSTEMIC INFLAMMATORY VASCULITIS
DISEASES OF BONE
8. Water, electrolytes and acid–base balance
WATER AND ELECTROLYTE REQUIREMENTS
BODY FLUID COMPARTMENTS
REGULATION OF BODY FLUID HOMEOSTASIS
PLASMA OSMOLALITY AND DISORDERS OF SODIUM REGULATION
DISORDERS OF POTASSIUM REGULATION
DISORDERS OF MAGNESIUM REGULATION
DISORDERS OF ACID - BASE BALANCE
9. Renal disease
INVESTIGATION OF RENAL DISEASE
URINARY TRACT INFECTION
HYPERTENSION AND THE KIDNEY
RENAL CALCULI AND NEPHROCALCINOSIS
URINARY TRACT OBSTRUCTION
ACUTE RENAL FAILURE/ACUTE KIDNEY INJURY
CHRONIC KIDNEY DISEASE
RENAL REPLACEMENT THERAPY
CYSTIC RENAL DISEASE
TUMOURS OF THE KIDNEY AND GENITOURINARY TRACT
DISEASES OF THE PROSTATE GLAND
10. Cardiovascular disease
COMMON PRESENTING SYMPTOMS OF HEART DISEASE
INVESTIGATIONS IN CARDIAC DISEASE
ISCHAEMIC HEART DISEASE
VALVULAR HEART DISEASE
PULMONARY HEART DISEASE
ARTERIAL AND VENOUS DISEASE
DRUGS FOR ARRHYTHMIAS
DRUGS FOR HEART FAILURE
DRUGS AFFECTING THE RENIN - ANGIOTENSIN SYSTEM
NITRATES, CALCIUM - CHANNEL BLOCKERS AND POTASSIUM - CHANNEL ACTIVATORS
11. Respiratory disease
12. Intensive care medicine
13. Drug therapy, poisoning, and alcohol misuse
14. Endocrine disease
PITUITARY HYPERSECRETION SYNDROMES
THE THYROID AXIS
MALE REPRODUCTION AND SEX
FEMALE REPRODUCTION AND SEX
THE GLUCOCORTICOID AXIS
THE THIRST AXIS
DISORDERS OF CALCIUM METABOLISM
DISORDERS OF PHOSPHATE CONCENTRATION
ENDOCRINOLOGY OF BLOOD PRESSURE CONTROL
DISORDERS OF TEMPERATURE REGULATION
15. Diabetes mellitus and other disorders of metabolism
16. The special senses
COMMON NEUROLOGICAL SYMPTOMS
COORDINATION OF MOVEMENT
THE CRANIAL NERVES
COMMON INVESTIGATIONS IN NEUROLOGICAL DISEASE
UNCONSCIOUSNESS AND COMA
STROKE AND CEREBROVASCULAR DISEASE
EPILEPSY AND LOSS OF CONSCIOUSNESS
NERVOUS SYSTEM INFECTION AND INFLAMMATION
HEADACHE, MIGRAINE AND FACIAL PAIN
SPINAL CORD DISEASE
DEGENERATIVE NEURONAL DISEASES
DISEASES OF THE PERIPHERAL NERVES