Platelet transfusion


Platelet transfusion, also known as platelet concentrate, is used to prevent or treat bleeding in people with either a low platelet count or poor platelet function. Often this occurs in people receiving cancer chemotherapy. Preventive transfusion is often done in those with platelet levels of less than 10 x 109/L. In those who are bleeding transfusion is usually carried out at less than 50 x 109/L. Blood group matching is typically recommended before platelets are given. Unmatched platelets, however, are often used due to the unavailability of matched platelets. They are given by injection into a vein.
Side effects can include allergic reactions such as anaphylaxis, infection, and lung injury. Bacterial infections are relatively more common with platelets as they are stored at warmer temperatures. Platelets can be produced either from whole blood or by apheresis. They keep for up to five to seven days.
Platelet transfusions came into medical use in the 1950s and 1960s. It is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system. In the United Kingdom it costs the NHS about £200 per unit. Some versions of platelets have had the white blood cells partially removed or been gamma irradiated which have specific benefits for certain populations.

Medication use

Prevention of bleeding

International guidelines recommend that platelets transfusions are given to people with reversible bone marrow failure to reduce the risk of spontaneous bleeding when the platelet count is less than 10 x 109/L. If the person is well using a higher platelet count threshold does not reduce the risk of bleeding further.

Prevention versus treatment of bleeding

A review in people with blood cancers receiving intensive chemotherapy or a stem cell transplant found that overall giving platelet transfusions when the platelet count is less than 10 x 109/L reduced the number of bleeding events and days with significant bleeding. However, this benefit was only seen in certain patient groups, and people undergoing an autologous stem cell transplant derived no obvious benefit. Despite prophylactic platelet transfusions, people with blood cancers often bleed, and other risk factors for bleeding such as inflammation and duration of thrombocytopenia should be considered.
There is little evidence for the use of preventive platelet transfusions in people with chronic bone marrow failure, such as myelodysplasia or aplastic anemia. Multiple guidelines recommend prophylactic platelet transfusions are not used routinely in people with chronic bone marrow failure, and instead an individualised approach should be taken.
Several studies have now assessed the benefit of using preventive platelet transfusions in adults with dengue who have profound thrombocytopenia.

Platelet transfusion threshold

Two reviews in people with blood cancers receiving intensive chemotherapy or a stem cell transplant found that overall giving platelet transfusions when the platelet count is less than 10 x 109/L compared to giving platelet transfusions when the platelet count is less than 20 or 30 x 109/L had no effect on the risk of bleeding.
Higher platelet transfusion thresholds have been used in premature neonates, but this has been based on limited evidence. There is now evidence that using a high platelet count threshold increases the risk of death or bleeding compared to a lower platelet count threshold in premature neonates.

Dose

A review in people with blood cancers compared different platelet transfusion doses. This review found no difference in the number of people who had clinically significant bleeding between platelet transfusions that contained a small number of platelets and those that contained an intermediate number of platelets. This review also found no difference in the number of people who had clinically significant bleeding between platelet transfusions that contained a small number of platelets and those that contained a large number of platelets. One of the review's included studies reported on transfusion reactions. This study's authors suggested that a high-dose platelet transfusion strategy may lead to a higher rate of transfusion-related adverse events.

Prior to procedures

In people with a low platelet count, prophylactic platelet transfusions do not need to be given prior to procedures that have a low risk of causing bleeding. Low-risk procedures include surgical sites that do not contain many blood vessels e.g. cataract surgery, or minor procedures.
Guidelines recommend that it is safe to perform central venous catheter insertion when the platelet count is 20 x 109/L or above. The evidence for this is based on observational studies in which bleeding occurred due to procedure error rather than due to the platelet count.
Platelet transfusion thresholds for more major procedures are based on expert opinion alone. Guidelines recommend a threshold of 50 x 109/L for major surgery and a threshold of 100 x 109/L for surgery on the brain or the back of the eye.
A Cochrane review was conducted in 2018. Estcourt et al. compared retrospective trials to determine the effect of platelet transfusions prior to a lumbar puncture or epidural anaesthesia for participants that suffer from thrombocytopenia. There was no age restriction and the participants additionally suffered from leukaemia or other haematological malignancies. People were excluded from study participation if they already got the diagnosis of a coagulopathy or if they already had a bleeding event in the past. Estcourt et al. conducted one analysis by comparing a platelet transfusion with no platelet transfusion: The evidence is very uncertain about the effect of platelet transfusions prior to lumbar puncture on major surgery-related bleeding within 24 hours and the surgery-related complications up to 7 days after the procedure.
Moreover, Estcourt et al. conducted a Cochrane review with randomised controlled trials in 2018 to measure the safety and effectiveness of prophylactic platelet transfusions prior to surgery for adult people that suffer from a low platelet count. The participants did not receive a treatment of the low platelet count before and they did not suffer from a bleeding event in the past. Moreover the included people suffered from chronic diseases or haematological malignancies. The exact inclusion and exclusion criteria and information regarding the dose of the intervention can be found in the original Cochrane review. Estcourt et al. conducted three different analyses. The first analysis compared the prophylactic transfusion to no transfusion: The evidence is very uncertain about the effect of prophylactic platelet transfusions on the all-cause mortality up to 30 days after surgery, the number of participants with major bleeding within 7 days of surgery, the number of participants with a minor surgery-related bleeding up to 7 days and the serious adverse events that are surgery-related and occur within 30 days. The second analysis was conducted to compare prophylactic platelet transfusions to alternative treatments: Prophylactic platelet transfusions may have little to no effect on the number of participants that suffer from a major bleeding up to 7 days after surgery, the number of participants with a minor bleeding that is related to the procedure and occurs within 7 days after surgery and the transfusion-related serious adverse events within 24 hours, but the evidence is very uncertain. The last analysis compared different thresholds to determine whether participants received a platelet transfusion: The evidence is very uncertain about the effect of different thresholds for platelet transfusions on the number of participants that suffer from a major bleeding within 7 days of surgery and the number of participants that suffer from a minor procedure-related bleeding that occurs within 7 days.

Treatment of bleeding

There is little evidence for the effectiveness of platelet transfusions or the optimal dose when a person with a low platelet count is actively bleeding. Current recommendations are based on consensus guidelines from around the world.

Side effects

Side effects can include allergic reactions such as anaphylaxis, infection, and lung injury. Bacterial infections are relatively more common with platelets as they are stored at warmer temperatures.

Usage

People with hematological disorders or cancer receive the largest proportion of platelet transfusions. Most are given to prevent bleeding during treatment with chemotherapy or stem cell transplant. Much of the remainder are used in general medicine, cardiac surgery and in intensive care.
Unlike other blood products demand for platelet transfusions appears to be increasing in several countries around the world. An ageing population, an increase in the number of people with blood cancer, and changes to the management of these cancers are likely the major reasons for the rise in demand for platelets. Since 1990, the number of stem cell transplants performed in Europe has risen from 4,200 to over 40,000 annually.

History

Platelet transfusions came into medical use in the 1950s and 1960s. It is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system.

Society and culture

In the United Kingdom it costs the NHS about 200 pounds per unit.

Manufacture

Platelets can be produced either from whole blood donations or by apheresis. They keep for up to five to seven days.
Platelet components can have had the white blood cells partially removed which decreases the risk of having a transfusion reaction. They can be treated with ultraviolet light which decreases the risk of transmission of certain infections. They can be gamma irradiated which have specific benefits for certain populations.