All blood within the UK is supplied by unpaid volunteers, before taking their blood, all are questioning thoroughly about their lifestyles and medical health. Each of the donations are then screened, however mainly the UK system relies on the donors honesty. However, adverse events may occur between donation to transfusion, and some of these are unavoidable.
Bacterial contamination
In order to minimise problems associated with bacterial blood contamination, the blood donation must be carried out in a way which is most aseptic as possible. The skin at the site of venepuncture must be cleaned with an antiseptic prior to donation. Bacteria which is airborne must also be taken into consideration. Patients may be suffering from an illness asymptomatically.
Storing the sample at a temperature of 4-6 degrees C is best in order to inhibit most bacterial growth, however some organisms such as Pseudomonas fluorescens are able to live at this temperatures, and if the bags are allowed to warm, the risk of bacterial proliferation increases, thus removing the bags from fridges in order to test them can cause issues.Bacterial proliferation which occurs in platelets is more of an issue than within RBCs, this is due to storage temperatures.
There will always be a risk of contamination from the donor, however in recent years this has decreased dramatically thanks to screening.
Human error
People may be at fault when it comes to transfusion contamination, such as placing the wrong blood in a tube, labelling a sample wrong, incorrect techniques in the lab, misidentification of an antibody on a contaminant, wrong patient transfused etc. Stress and tiredness can cause these mistakes to occur, however they can be life threatening in some cases. This is why doctors are required to have adequate training to carry out such a procedure.
A scientist has a large responsibility from beginning to end, they test, store and issue blood, and also investigate any adverse reactions.
Blood safety regulations
Any serious adverse blood reactions and events (SABRE) from a transfusion must be reported to the Medicines and Healthcare Products Regulatory Agency (MHRA), this agency is associated with the Department of Health, and is responsible for ensuring medications and medical devices work and are safe. The agencies role is to enforce standards laid down by the EU Blood Directive. Hospital blood banks must demonstrate they're complying with standards.
SHOT
Serious hazards of transfusion: was created due to concern over absence of data available in relation to safety of transfusion and adverse events. It is a voluntary, anonymous confidential reporting scheme. It collects and reports data for adverse events in transfusions, it has a wider scope than the MHRA as the reports come from clinical and professional areas of practice as well as transfusions carried out in a hospital. They provide an annual report giving their findings and recommendations. SHOT is beneficial as it provides an aid in guideline production, improving standards and minimising adverse events via education.
SHOT abbreviations for adverse reaction reasons:
- IBCT: incorrect blood component transfused
- I&U: inappropriate, unnecessary and under/delayed transfusions
- HSE: handling storage errors
- ATR: acute transfusion reactions
- HTR haemolytic transfusion reactions
- TRALI: transfusion-related acute lung injury
- TACO: transfusion-associated circulatory overload
- TAD: transfusion-associated dyspnoea
- PTP: post-transfusion purpura
- Ta-GvHD: transfusion associated graft versus host disease
- TTI: transfusion transmitted infection
Acute intravascular haemolysis
This is the adverse reactions caused from the transfusion of red blood cells, this usually occurs due to the incompatibility of the donors blood type with the patient, such as ABO. The RBCs will be destroyed rapidly by antibodies against that blood type, which will release free haemoglobin into the blood, this can lead to disseminated intravascular coagulation (DIC), shock, acute renal failure and maybe death.
Shock phase: symptoms include vomiting, headache, shortness of breath, fall in blood pressure and a raise in body temperature (pyrexia), this can occur at any time from the blood being transfused, even if it's only a small amount. This will be accompanied by increase RBC destruction and DIC.
Oliguric phase: acute renal failure and acute tubular necrosis may occur.
Diuretic phase: fluid and electrolyte imbalance may occur during recovery.
AIH can be tested for in the laboratory, tests can be conducted in order to determine, within the blood, the amount of:
- Haptoglobins (free haemoglobin transporter, for recycling, produced by the liver)
- Bilirubin (a product of haemolysis)
- Haemoglobin
- RBC count
- Reticulocytes
- Nucleated RBCs
- Polychromasia (abnormal amount of RBCs due to being released from bone marrow prematurely)
- Fragmented RBCs
- Antiglobulin
Compatible blood types
Patient A - can receive donor A and O
Patient B - can receive donor B and O
Patient O - can receive donor O
Patient AB - can receive donor A and B and O and AB
Other factors do play a role such as antigens for other proteins that the patient or donor may possess.
Delayed transfusion reactions
Adverse reactions due to red blood cell transfusions, involving extravascular haemolysis. Involves antibodies that are not able to activate complement, e.g Abs to the E or Kidd Ags. This is usually a result of a patients response who has previously been sensitised against a particular Ag by transfusion or pregnancy. It is less severe than intravascular haemolytic reactions. Abs are present at low levels, thus not always detected in the pre-transfusion samples. Cells acquired from the donor will become coated with IgG, and are then removed by the reticuloendothelial system. The symptoms of this can be progressive anaemia, possibly with the presence of jaundice. The patient must have their blood pressure and renal perfusion maintained, if failure of these occur, this may be managed with dialysis until the patient is recovered. The patient will require more transfusions with the appropriate blood type
Iron overload
Those patients who undergo many transfusions may result in acquiring an iron overload. Examples of this include patients who are dependent on transfusions, such as those suffering from thalassaemia, myelodysplasia, or myeloproliferative disease. The consequences of this will cause adverse effects on the liver, heart and endocrine glands, all with clinical consequences. The treatment for this is iron chelation therapy.
TA-GVHD
Transfusion-associated graft-verses-host disease, occurs when live lymphocytes are transfused into immunocompromised patients, causing clonal expansion of viable lymphocytes. Examples include premature babies, and bone marrow transplant patients. This is quite rare, however when it does occur it can be fatal; thus its prevention is a high priority.
TRALI
Transfusion related acute lung injury, this is caused by HLA Abs from donor plasma, which has been transferred to the patient during a transfusion. These Abs cause complement-mediated cellular damage to the endothelial and epithelium of the lungs. Symptoms for this include fever, chills, coughing and increased distress on the respiratory system.
TACO
Transfusion-related circulatory overload. Can be caused via inappropriate transfusions from sampling errors, or inappropriate blood requesting. It can also be caused by a laboratory error, and also transfusing blood into patients too quickly. This can result in cardiac failure and cardiac arrest. Some patients will be more prone to circulatory overload than others, such as those with renal disease and previous cases of heart failure.
PTP
Post-transfusion purpura, this is another reference for acute thrombocytopenia, which is basically the presence of anti-platelet antibodies already within the recipient patients body, which could have developed from a previous transfusion or during pregnancy. This can occur 5-12 days after a transfusion of RBCs or platelets has taken place, this can lead to severe thrombocytopenia and subcutaneous bleeding. Both the transfused and original platelets are destroyed by immune complexes.
FNHTR
Febrile non-haemolytic transfusion reaction, caused by antibodies present in the recipients blood against donor leukocytes, and also HLA antigens. The use of cytokines is used to mediate the reaction, and leukoreduction of any future transfusions can be performed. The symptoms of this can be fever.
Allergic reaction
Most common reaction from a transfusion, occurs in all types of product however less so with RBCs. Most reactions are mild.
Anaphylactic reactions
These tend to be associated with IgA deficiency, of haptoglobin deficiency. Very common in Asian patients.
Ways to reduce the need for transfusion
Correction of anaemia prior to operation, attempting to salvage cells, lower the trigger levels for RBC transfusion. Avoiding aspirin also helps, also trying biological alternatives, such as recombinant clotting factors and erythropoietin.
Transfusion monitoring and adverse incident reporting
Patients whom are receiving a transfusion of any type of blood product or component must be monitored closely for the first 15 minutes of after a transfusion, this is so that any early signs of incompatibilities or bacterial contamination can be detected. A patient is monitored via the monitoring of their temperature, pulse, blood pressure and respiration rate. Monitoring will be undertaken regularly afterwards incase of any delayed reactions. All transfusion bags should be kept for a minimum of 24 hours. If an adverse reaction occurs, the hospital transfusion lab would be informed, as well as the haematology medics. If there are any suspected bacterial or viral infections caused by transfusions, this should be reported as quickly as possible to the local blood service centre.
If a reaction has occurred:
Stop the transfusion, re-test the samples from the patient to check their blood type and cross match with the donor type, post and pre transfusion to ensure original test was correct. Identify any Ab present. Carry out an anti-globulin test, check the colour of a patients plasma and urine for any signs of haemolysis. Check for clerical errors, and check appearance of blood, plus ABO group and Rh group of donor units. Always send for microbiological testing: samples will be taken from the donor unit, side tube and giving set, this is to check where the contamination or error arose from.
Overall, the majority of transfusions are successful. This is due to the current quality procedures in place. It has been estimated that the number of reports in regards to transfusions reactions are less than what may occur, so it is suggested that the real number of cases is unknown. However, SABRE and SHOT reports still give a good insight and important information about the adverse events that do occur.
