What Is The Pathology Of Mild Allergic Reaction
The pathology of mild allergic transfusion reaction is:
-Etiology: The cause of mild allergic transfusion reaction is administration of the wrong blood, hypersensitivity, presence of histamines and bradykinins.
-Genes involved: None.
-Pathogenesis: The sequence of events that lead to mild allergic transfusion reaction is when that antibodies are formed against the components of the donors blood and are mediated to attack them.
-Morphology: NA.
-Histology: NA.
Pearls And Other Issues
Transfusion reactions are influenced by many factors including the type of component being transfused, the storage requirements, and the patients co-morbid conditions at the time of transfusion. Understanding how to quickly identify transfusion reactions and appropriately manage and treat the patient ensures optimal patient care.
What Is A Blood Transfusion
Blood transfusion can be life-saving and provides great clinical benefit to many patients but it is not without risks:
- Immunological complications.
- Errors and ‘wrong blood’ episodes – the Serious Hazards of Transfusion report for the UK documented that an error incidence of 2,623 of just over 2 million components transfused in 2020.
- Immunomodulation.
Growing awareness of avoidable risk, and improved reporting systems, have led to a culture of better safety procedures as well as steps to minimise the use of transfusion. The reporting rate of transfusion errors is improving although un-reporting of some serious adverse reactions still occasionally occurs.
Alternative approaches to patient management should be used to reduce or eliminate the need for transfusion whenever possible.
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How Is A Blood Transfusion Reaction Treated
The first step in treating a transfusion reaction is to immediately stop the transfusion if it is still being delivered. Your veterinarian will then provide supportive care for your dog. This care often includes IV fluids to help maintain appropriate blood pressure. Your veterinarian will then administer medications specific to the type of reaction that your dog is experiencing.
“The first step in treating a transfusion reaction is to immediately stop the transfusion…”
In the case of an allergic reaction, your veterinarian will administer antihistamines and/or epinephrine to stop the reaction. Patients with hemolytic reactions may receive prolonged courses of immunosuppressive drugs. Your veterinarian may give antibiotics if bacterial contamination is suspected or diuretics if a fluid overload is suspected.
Types Of Transfusion Reactions

When getting a blood transfusion, there are many different types of transfusion reactions that may occur. These include:
- Acute hemolytic reactions. This can happen if there’s red blood cell damage before the transfusion due to heat or an imbalance in the cells.
- Simple allergic reactions. This may happen if your blood is hypersensitive to protein in your donor’s blood.
- Anaphylactic reactions. This is similar to a simple allergic reaction but is more severe.
- Transfusion-related acute lung injury . Damage to the lungs occurs when your body reacts to your donor’s antibodies. Your immune system responds to the reaction by releasing chemical mediators that cause edema in the lungs.
- Delayed hemolytic reactions. This may happen when an antigen gets reintroduced into your blood.
- Transfusion-associated circulatory overload . This may happen when you get too much blood in the body.
- This may happen when your donor’s white blood cells produce cytokines .
- This may happen if the blood is contaminated with bacteria or bacteria waste products.
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How Is A Blood Transfusion Reaction Diagnosed
In many cases, a transfusion reaction can be diagnosed based on clinical signs alone. If new clinical signs develop during or immediately after a blood transfusion, a transfusion reaction is frequently the cause of these signs. The diagnosis of a transfusion reaction may be confirmed using blood tests, urinalysis, or other tests such as X-rays. The specific tests performed to diagnose a transfusion reaction will vary depending on the type of transfusion reaction that your veterinarian suspects.
Transfusion Support For Patients With A History Of Anaphylactic Transfusion Reactions
For patients with a history of anaphylactic transfusion reactions, ideally, an investigation would be done to determine if anti-IgA antibodies are present. Transfusion management of patients with a history of an anaphylactic transfusion reaction and anti-IgA antibodies is outlined in Table 2. If the patient is not IgA deficient and/or no anti-IgA has been detected, and the patient has experienced only a single anaphylactic reaction, a trial transfusion of unwashed blood components may be performed under controlled conditions, including patient consent, premedication, and close medical supervision. If an anaphylactic reaction occurs again, the patient should be transfused using components washed to remove the maximal amount of plasma.3,24 For red blood cells, a double wash protocol is necessary to adequately reduce IgA levels to less than 0.05 mg/dL using an automated cell processor .24 If there is inadequate time to perform testing for anti-IgA, the case should be discussed with a Canadian Blood Services medical officer.
Table 2: Transfusion management of patients with a history of an anaphylactic transfusion reaction and anti-IgA antibodies.
- Clinical algorithm. Print out the algorithm to aid decision making on IgA and anti-IgA testing for patients requiring transfusion therapy.
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Testing Patients For Anti
Individuals with a history of an anaphylactic transfusion reaction or two severe allergic reactions may benefit from further IgA level and anti-IgA testing. However, the utility of performing testing on patients who appear to have low IgA levels but have not been transfused, or have not had a transfusion reaction is unclear.21-23 Given the high frequency of anti-IgA antibodies and the low frequency of anaphylactic transfusion reactions attributable to anti-IgA, it is estimated that approximately 1 in 100 patients with IgA deficiency and anti-IgA antibodies develop transfusion reactions. There is no available test to distinguish which anti-IgA antibodies may be of clinical significance. A positive result in patients where anti-IgA testing is not indicated may result in unnecessary delays in transfusion due to uncertainty about the requirements for specialized products, or clinical hesitation to transfuse due to fear of a transfusion reaction. Therefore, the majority of practitioners do not recommend testing of patients who are low in IgA for the presence of anti-IgA, in the absence of a history of an anaphylactic transfusion reactions.21 Moreover, if previous testing for IgA has shown detectable levels and/or previous anti-IgA testing has shown no detectable anti-IgA antibodies, further testing for anti-IgA is not recommended.
At Canadian Blood Services, anti-IgA testing may be considered in the following patients :
Packed Red Blood Cells
Packed Red Blood Cells or PRBCs are given to patients when their hemoglobin levels are low. This is called anemia. Some common causes of anemia that may need a transfusion include:
- Acute and chronic blood loss
- Untreated ongoing Anemia
- Destruction of blood cells
PRBCs are usually ordered when hemoglobin levels drop below 7g/dL, but it depends on the nature of the patients anemia as well as their medical history and their hemodynamic stability
1 to 2 units will be ordered of PRBCs depending on how low the patients hemoglobin level is, as well as if there is active blood loss. Each unit of PRBCs should increase the hemoglobin by about 1g/dL.
Before blood products are given, a type and screen is done to verify the patients blood type and screen for any antibodies that may require special blood. The exception is if the patient has significant ongoing hemorrhage and the patient needs emergent blood. In this case, O Negative blood is given as they are the universal donor.
Each unit of blood will take about 2 hours to transfuse, but the maximum amount of time is 4 hours when the blood will expire. In emergencies, blood can be run as fast as needed, often with pressure bags.
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Why Are Blood Products Given
Blood products are given whenever the blood levels are too low, or when there is acute bleeding. While this will depend on each specific patient and clinician, blood products are generally given when:
- PRBCs are given when hemoglobin is below 7 or there is ongoing blood loss with hemodynamic compromise
- Platelets are given when active bleeding with levels < 50K, or when < 10K.
- FFP is given with massive blood transfusions, severe liver disease or DIC, or as a coumadin reversal option.
Donor And Patient Characteristics
ATRs can occur repeatedly in some patients, suggesting that hypersensitivity or susceptibility may play an important part in the development of these reactions.26 As ATRs occur more frequently with platelet and plasma transfusions compared to red blood cell transfusions, it has been hypothesized that the donor antibody and allergen attributes at the time of donation may have a role in mediating ATRs. In one analysis comparing overall institutional ATR rate to the concordance rate of ATRs for split apheresis platelet components transfused to at least two different recipients, no difference was observed and suggested that donor factors were not a significant influence on ATRs.26 However, when donors of split components associated with concordant ATRs in two or more recipients were queried for development of ATRs in other recipients of other components from these same donors, a significantly higher ATR rate was observed compared to the overall ATR rate , leaving open the possibility that donor factors may influence the ATR rate.
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TRALI
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Acute Hemolytic Transfusion Reaction
An acute hemolytic transfusion reaction is a rare life-threatening blood transfusion reaction to receiving blood, specifically PRBCs.
This happens when incompatible blood is accidentally infused with the patient. This is why the patients blood type is checked in the first place so that an appropriate donor can be given.
Compatible blood is outlined below:
When having a true acute hemolytic reaction, the patient will quickly experience:
- Fever and/or chills
- Severe flank pain or back pain
- Urine turning red or brown
This is a severe reaction as the patients own immune system and the donors immune system attack each other, destroying blood products and causing damage in the process. The patient may experience hemodynamic instability including life-threatening hypotension.
If this reaction occurs, the nurse should:
What Causes A Blood Transfusion Reaction

Your immune system can react to anything in the donor blood. One of the most serious reactions is called ABO incompatibility. The 4 main blood types are A, B, O, and AB. Your immune system will try to destroy donor cells that are the wrong type for you. Another reaction happens when you are allergic to something in the donor blood. Allergic reactions are usually mild but can become a life-threatening reaction called anaphylaxis.
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How Is A Blood Transfusion Reaction Diagnosed And Treated
Your blood and urine will be tested for signs of kidney failure or destroyed red blood cells. You may need any of the following to treat a reaction:
- Medicines may be given to decrease itching and swelling from a mild reaction. Epinephrine is an emergency medicine given when antihistamines do not stop an allergic reaction. You may also need medicine to relax muscles in your throat and chest to help you breathe, or to raise your blood pressure. Medicine may also be given to lower a fever.
- Fluids may be given through your IV to prevent your blood pressure from falling too low. IV fluids will also help your kidneys get rid of donor red blood cells that your immune system has destroyed.
Blood Transfusion Reactions: A Comprehensive Nursing Guide
William J. Kelly, MSN, FNP-C
Blood transfusion reactions are common within the hospital setting because so many blood products are given. Transfusing blood products that are lacking or actively being lost is literally life-saving treatment.
In this article, we will talk about the different blood products, why they are given, and then dive into each type of blood transfusion reaction, what causes them, their signs and symptoms, and how to manage them as the nurse.
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Development Of Antibodies To Red Cells In Patient’s Plasma
- Transfusion of red cells of a different phenotype to the patient’s will cause alloimmunisation – for example, development of anti-RhD in RhD-negative patients who have received RhD-positive cells.
- This is dangerous if the patient later receives a red cell transfusion, and can cause haemolytic disease of the newborn .
Blood Transfusion Reaction Symptoms
Symptoms or signs may occur after only 5-10 ml of transfusion of incompatible blood so patients should be observed closely at the start of each blood unit transfused.
Symptoms
- Feeling of apprehension or ‘something wrong’.
- Pain at the venepuncture site.
- Pain in the abdomen, flank or chest.
- Shortness of breath.
- Fever and rigors.
- Hypotension or hypertension.
- Oozing from wounds or puncture sites.
- Haemoglobinaemia.
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Delayed Haemolysis Of Transfused Red Cells
- In those who have previously been immunised to a red cell antigen during pregnancy or by transfusion, the level of antibody to the blood group antigen may be so low as to be undetectable in the pre-transfusion sample.
- However, after transfusion of red cells bearing that antigen, a rapid, secondary immune response raises the antibody level drastically, leading to the rapid destruction of transfused cells.
- 5-10 days post-transfusion, patients present with fever, falling Hb , jaundice and haemoglobinuria.
- A rise in bilirubin and positive DAT will also be present.
What Are The Signs And Symptoms Of A Delayed Reaction
A delayed blood transfusion reaction can begin within 3 to 10 days. You may also have a reaction the next time you receive blood.
- A high fever and chills
- Dizziness or fainting
- Headaches, double vision, or seizures
- Yellowing of your skin or the whites of your eyes
- Chest pain or shortness of breath
- Bruises, fatigue, or weakness
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Physical Findings & Clinical Presentation
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Fever, chills, nausea, tachycardia, chest pain, dyspnea, dizziness, bronchospasm.
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Lower back pain due to ischemic muscle pain or vasospasm hypotension.
-
Severe reactions may occur in surgical patients under anesthesia who are unable to give any warning signs.
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Patients with delayed hemolytic transfusion reactions typically do not present as a clinical emergency. In most cases, presentation is with a low-grade fever from the generation of IL-1 or other proinflammatory cytokines. Hemoglobinuria and hemoglobinemia are rarely present. Unexplained anemia and jaundice are other possible presentations.
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Tables 1 and2 summarize signs and symptoms of acute adverse reactions to blood transfusion. In the differential diagnosis of hemolysis.
James Palis MD, in, 2007
Acute Hemolytic Reaction: Nursing Steps

If an acute hemolytic reaction is suspected, the nurse should:
The Provider should guide treatment, but these are serious reactions and would likely need monitoring in the ICU.
Your facility should have a specific protocol in the event of significant blood transfusion reactions, which often involves re-testing the patient as well as re-testing the blood unit itself.
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Graft Versus Host Disease
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GVHD is a situation where transfused lymphocytes engraft and multiply in immunocompromised patients . The newly engrafted lymphocytes attack the host. This is the opposite of a host rejecting a transplanted organ .
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Transfusion-associated graft versus host disease is a different disease from GVHD in allogeneic bone marrow transplant recipients. TAGVHD is uniformly fatal and untreatable. It occurs when the blood products contain T-lymphocytes and attack many host tissues. It occurs when the recipient is immunocompromised
- TAGHVD is prevented by gamma-irradiating the blood products to be transfused.
Investigation Of Patients With Anaphylactic Transfusion Reactions
If a patient develops an anaphylactic transfusion reaction, a comprehensive assessment should be performed to assess both transfusion-related and unrelated causes of anaphylaxis.
Depending on the clinical scenario, screening tests may include immunoglobulin quantification for IgA levels as well as haptoglobin levels. If, based on immunoglobulin quantification, the patient appears to be IgA deficient, samples should be sent to Canadian Blood Services to determine if anti-IgA is present.
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How Can I Help Prevent Another Blood Transfusion Reaction
- Give complete health information. Tell your healthcare providers about your health conditions, transfusions, and pregnancies.
- Alert your healthcare providers about any problems. Tell your healthcare providers right away if something feels wrong. They will stop the transfusion and treat your symptoms. Pain, nausea, itching, or a large bruise at the transfusion site are good reasons to stop the transfusion.
- Ask if you can use your own blood. You may be able to get your own blood during surgery. Your blood will need to be drawn and stored a few weeks before a scheduled surgery.
- Carry medical alert identification. Wear jewelry or carry a card that says you had a blood transfusion reaction. Healthcare providers may give you medicine before the transfusion to prevent a reaction.
Alloantibodies Against Red Cells
These include naturally occurring antibodies, particularly anti-A and -B, and immune antibodies induced by previous transfusions and/or pregnancies. Except in exceptional cases blood transfusion reactions due to red cell antibodies should not occur. The correct determination of the ABO blood group of donor and recipient, correct antibody detection and cross-matching and correct patient identification should prevent such reactions. Because donor red cells are destroyed when a reaction is caused by red cell antibodies, such reactions are called hemolytic.
The signs and symptoms of the reaction are due on one hand to the liberation of hemoglobin and thromboplastic substances in stroma, and on the other to the activation of complement, leading to the liberation of C3a and C5a which increase vascular permeability, stimulate mast cells to liberate vasoactive substances such as histamine, and macrophages to liberate cytokines such as interleukin-1 .
When ABO incompatible red cells are transfused the reaction is usually severe: the patient becomes restless and complains of a feeling of oppression, which is often accompanied by substernal pain. The patient may have abdominal pain and may vomit.
Kathleen M. Madden MD, Jay S. Raval MD, in, 2020
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