Overview of Platelet Transfusion
The practice of giving blood transfusions has come a long way since the first attempts in the 1600s. Instead of transfusing whole blood from one person to another, now doctors can just give the parts of the blood a patient needs. This can include red blood cells, platelets, white blood cells, and plasma.
Platelets are very important in helping blood clot. This was discovered in the 1950s and 1960s when doctors noticed patients with leukemia who were getting chemotherapy had serious bleeding problems. The fact that plastic bags could keep platelets working properly was a big game-changer for keeping donated blood useful. Another huge leap in blood transfusion was the technique to separate out the platelets, so doctors could give platelets specifically. There have been many efforts to improve safety and to make adverse reactions to blood transfusions less likely.
Platelets are most often used to treat a condition called thrombocytopenia – a low number of platelets. This can happen for a variety of reasons including cancer of the blood cells, failure of the bone marrow, and other causes of platelet destruction. It’s very rare for platelets to be given when normal levels are present. Platelets are valuable because they only last for 5 days and therefore are included in the World Health Organization’s Essential Medicines list.
Anatomy and Physiology of Platelet Transfusion
The platelets are small, disc-shaped cells found in our blood, with diameters varying between 2.0 to 5.0 micrometers, and they are as thin as 0.5 micrometers. They are created in the bone marrow, which is the spongy tissue inside larger bones, through a process called megakaryopoiesis from stem cells. Certain growth factors, especially thrombopoietin, play a key role in this process. On average, our body produces and releases about 100 billion new platelets every day. The lifespan of a platelet is generally between 8 to 10 days. After this period, the liver helps in removing and breaking down the old platelets.
Platelets have several important functions, mainly helping the blood to clot and prevent excessive bleeding when we are injured. They stick to the damaged area, release special substances that promote clotting and gather together to form a clot or plug. Moreover, platelets assist in reducing inflammation, heal wounds, stimulate cell growth, and strengthen the body’s defense against infections.
Internally, a platelet has 3 main zones or areas:
- The peripheral zone: This outer layer is responsible for sticking to injured areas and binding with other platelets. It includes the glycocalyx, a carbohydrate-rich structure, essential for forming clots where it attaches the platelets together by linking to a protein called fibrinogen. Another crucial element is the unit membrane, which helps speed up the clotting process. It covers the platelet and has a system of small canals, which aids in carrying signals from the platelet surface to its internal structures, thus controlling platelet activity.
- The sol-gel zone: This middle portion provides structural support to the platelet, aiding in changes during clotting and storing the platelet’s internal structures.
- The organelle zone: This internal part of the platelet is where it stores many important substances. Alpha and dense granules hold various proteins, chemicals, and factors needed for clotting and immune response. Mitochondria, known as the powerhouse of the cell, provide energy. Glycogen supplies carbohydrate fuel, and lysosomes and peroxisomes play critical roles in defending the body against harmful elements.
When platelets get activated due to an injury, they release the substances stored in the alpha and dense granules to ensure rapid clotting while boosting the immune response.
Why do People Need Platelet Transfusion
The number of platelets, a kind of blood cells responsible for stopping bleeding, in a healthy person’s blood ranges from 150,000 to 450,000 cells per microliter. Sometimes, people may have lower numbers or their platelets might not function well. In such cases, they might need platelet transfusion, a treatment that involves giving platelets to a person through their vein.
Decisions about when to give platelet transfusions depend on the situation. For people who are bleeding, platelet transfusion might be needed if the count drops below certain levels. If a person has very severe bleeding, like in disseminated intravascular coagulation, a condition where many small blood clots form throughout your body’s small blood vessels, transfusion is suggested if the count drops below 50,000 cells per microliter. In cases of less severe bleeding and when life is not at serious risk, transfusion is necessary if the count drops below 30,000 cells per microliter. In situations of multiple injuries or bleeding within the skull, transfusion is advised if the count drops below 100,000 cells per microliter.
Sometimes, platelet transfusions are given to prevent bleeding, particularly before a person undergoes certain procedures or when counts fall very low. For example, if a person’s count drops below 10,000 cells per microliter, a transfusion might be given to stop bleeding from starting. Before major surgeries and in disseminated intravascular coagulation, the threshold for transfusion is below 50,000 cells per microliter. In specific procedures that involve inserting a central line or epidural anesthesia, transfusions are given if the count is below 20,000 or 80,000 cells per microliter respectively. The thresholds are different again for other surgical or therapeutic procedures.
In certain settings, platelet transfusion practices may be different. For example, in idiopathic thrombocytopenic purpura, a condition in which the immune system mistakenly attacks platelets, transfusion is avoided unless severe bleeding occurs. For patients going through chemotherapy, transfusion is advised when the count is less than 20,000 cells per microliter. Transfusion is necessary for people undergoing heart surgery if they have low platelet count and are bleeding.
Platelet transfusions are also given to children, but the thresholds may be different. For newborns who are stable but have platelet counts below 30,000 cells per microliter, transfusion is suggested. For newborns weighing below 1500 grams at birth or less than a week old, or infants who are not stable, the threshold is 50,000 cells per microliter. This is also applicable for an infant undergoing a surgery or experiencing considerable bleeding.
When a Person Should Avoid Platelet Transfusion
There’s only one main reason why someone might not be able to safely receive a transfusion of platelets (cells that help our blood to clot): they have a disease called thrombotic thrombocytopenic purpura. This condition increases the risk of forming blood clots to a dangerous level. But the impact of this on patient outcomes and death rates isn’t clear-cut as studies have shown a mix of results.
Platelet transfusions are generally only used in emergency situations when someone is experiencing severe, life-threatening bleeding.
In the past, it was thought that having a platelet transfusion increased the risk of forming blood clots for those with a condition known as heparin-induced thrombocytopenia. But recent studies suggest this may not be the case. However, in those patients, platelet transfusions are only done before or during a medical procedure, or if severe bleeding is present. They are not recommended as a preventative measure for these patients.
Equipment used for Platelet Transfusion
Platelets, which help blood clot, are given directly into the patient’s veins using a tube equipped with a special filter. This filter has very small holes (170 to 260 micrometers), small enough to catch any unwanted clots or other large particles in the platelets before they enter the patient’s body. The tube can be prepared with normal saline (salt water solution) or the platelets themselves.
In case of an emergency during the procedure, supplies such as normal saline,a source of oxygen, and medications to treat severe allergic reactions (anaphylaxis) should be on hand. This ensures that immediate response can be provided in the event of any negative reaction to the platelet transfusion.
Who is needed to perform Platelet Transfusion?
When a patient needs a platelet transfusion, various medical specialists work together to ensure it goes smoothly. In simple terms, platelet transfusion is giving the patient more platelets, which are tiny blood cells that help stop bleeding. First, the main doctor, also known as a clinician, checks the patient’s health and decides if a platelet transfusion is necessary. They tell the other medical staff about their decision.
The actual process of giving the platelets to the patient is often done by a special nurse known as a transfusionist. This nurse has specific training to safely perform transfusions. Before starting the transfusion, the transfusionist needs to make sure they have the right patient and the correct platelet units. This is to ensure the patient’s safety and the success of the therapy.
Preparing for Platelet Transfusion
To prepare for a platelet transfusion, the first step is to ensure we have quality-approved platelet concentrates. Platelets are small cells in the blood that help form clots to stop bleeding. These can be obtained in two ways: from whole blood or by a process called apheresis, which separates platelets from other blood components. In adults, the usual dose for preventative therapy is 4 to 6 units. For children, the dose depends on their weight, usually between 5 to 10 mL per kilogram. Platelet concentrates can be stored for up to 5 days.
Before a transfusion, it is crucial to check the patient’s and the donar’s blood types match to avoid an adverse reaction. This is done by the blood bank and confirmed by verifying the blood type of the patient and the platelet concentrate. Usually, it’s best to match platelet groups, but in emergencies like severe bleeding, it might be necessary to do a cross-group transfusion. Crossmatching, a more thorough comparison of blood, is rarely required unless the platelet concentrate has a lot of red blood cells.
The patient’s consent is required before making an order for a platelet transfusion from the blood bank. Also, an intravenous line must be prepared before the platelets arrive. Careful checks are made to ensure the patient’s identification, unit numbers, blood type, and search for any signs of infection in the platelet bag.
If a patient requires any special procedures, these should be noted on the request form. Procedures like leukoreduction and irradiation can help reduce the risk of complications. Leukoreduction filters out white blood cells to prevent a reaction, and irradiation stops a complication called graft-versus-host disease, a reaction where the patient’s body rejects the transfused platelets.
How is Platelet Transfusion performed
When you need a transfusion, the doctor will place a small intravenous (IV) tube into a vein on your hand or arm. This tube is called a “cannula” and comes in different sizes. For adults, a medium-sized cannula (18-22 gauge) is typically used, while children usually need smaller ones (25-26 gauge). Sometimes, if a tube cannot be placed in a vein, it might be necessary to place it inside a bone.
Before starting the transfusion, your doctor or nurse will record your vital signs (like heart rate, temperature, and blood pressure). Then, the bag containing the donor platelets (parts of the blood that help with clotting) is connected to your IV line in a sterile way. This is done using a special kind of hose, which has a filter to ensure the blood is clean before entering your body.
Usually, the transfusion is given slowly over 30 to 60 minutes. However, if there’s an emergency, it can be given faster. If you’re at risk of having too much fluid in your body, the transfusion might be given more slowly.
While the transfusion is happening, your vitals will be checked every 15 minutes to make sure your body is reacting positively. If there are any signs that you’re having a bad reaction to the transfusion, the process will be stopped right away and your doctors will quickly take the necessary steps to make sure you’re safe.
Possible Complications of Platelet Transfusion
Having a platelet transfusion can sometimes come with some side effects that range from mild to serious. The more common and manageable side effects and how they are treated are outlined here.
Febrile Nonhemolytic Transfusion Reaction is one of the typical problems and occurs in about 0.09% to 27% of cases. It’s usually recognised by fever and chills either during or within four hours of the transfusion, with no other clear cause. It’s known to happen due to factors present in white blood cells during storage or reactions between donors’ and recipients’ cells. The safest method to avoid this reaction is to deplete white blood cells prior to storing them. If the reaction should happen, transfusion is stopped, lab tests are taken to eliminate the possibility of a ‘hemolytic transfusion reaction’, other causes of fever are looked into, and antipyretic medication (for fever reduction) and meperidine or pethidine (for chills) are given.
Allergic reactions can also happen and are among the most frequent transfusion reactions, with about 1% to 3% incidence. Symptoms show up as itching, hives, or local skin swelling and can occur within four hours of a transfusion. To deal with this, the blood transfusion is stopped and antihistamines are administered. In severe cases, additional medication may be given. Possible preventative measures include reducing plasma in platelet preparations.
Anaphylactic reactions are rare and can occur in patients with an immunoglobulin A (IgA) deficiency when anti-IgA antibodies target IgA-containing platelets. Symptoms like low blood pressure, swelling and spasms leading to difficulty breathing appear rapidly. This is a medical emergency that needs urgent attention. To prevent this, platelets are washed or taken from IgA-deficient donors.
Transfusion-associated graft-versus-host disease is a rare but deadly problem, leading to fever and symptoms affecting organs like the skin, digestive tract, liver, and bone marrow. Prevention is achieved by irradiating platelets.
Transfusion-related acute lung injury is a life-threatening issue that leads to oxygen deficiency in the lungs during transfusion or within 6 hour of stopping, with no evidence of lung injury prior to therapy. To prevent this, plasma is reduced in platelets and replaced with a solution that helps avoid this issue.
Posttransfusion purpura is a rare side effect that involves severe thrombocytopenia (low platelet count), which can cause bleeding, or tiny purple or red spots on the skin due to bleeding beneath the skin. Diagnosis is achieved by demonstrating alloantibodies directed against human platelet antigens.
What Else Should I Know About Platelet Transfusion?
Platelets are vital components of our blood because they perform complex functions that no other blood cells can do. They are responsible for stopping bleeding by clumping and clotting at the site of blood vessel damage.
The process of collecting, treating, storing, and transfusing platelets involves several health professionals and needs to be performed with high accuracy and expertise. Due to the risks associated with receiving a transfusion of platelets, it’s crucial to weigh these risks against the benefits before proceeding with this procedure.
Just like other medical fields, transfusion medicine, which handles the transfusion of blood and its components, including platelets, is always changing and improving. Its main aim is to lower the risks mentioned above and improve the overall health results for patients having the procedure.
