What are the risks of platelet transfusion in dengue patients?

As the number of dengue patients is on the rise, it is important to know the risks of platelet transfusion and when it is required for dengue patients. Transfusion for a dengue patient is required only if their platelet count is below 10,000 and there is spontaneous, active bleeding.

“It is a myth that all dengue patients require platelet transfusion. In fact unnecessary transfusion causes more harm and puts the patient at risk of complications such as sepsis, transfusion-related acute lung injury (TRALI), transfusion-associated circulatory overload (TACO), allo-immunisation and allergic and anaphylactic transfusion reactions” says Dr KK Aggarwal, President HCFI & Honorary Secretary General IMA and a Padma Shri awardee.

Read: Dengue: Facts and prevention measures

Other risks of platelet transfusion include: 

• Febrile non-hemolytic transfusion reactions (FNHTR), 
• Transfusion-associated graft-versus-host disease (ta-GVHD), and
• Post-transfusion purpura (PTP).

Aggarwal says it is important "while treating dengue patients, physicians should remember the ‘Formula of 20'".

That includes:

• Rise in pulse by more than 20
• Fall of BP by more than 20
• Difference between lower and upper BP less than 20 
• Presence of more than 20 hemorrhagic spots on the arm after a tourniquet test suggest a high-risk situation, which needs immediate medical attention.

The primary cause of death in dengue patients is capillary leakage, which causes blood deficiency in the intravascular compartment, leading to multi-organ failure.

It is important that fluid replacement  be administered to the patient amounting to 20 ml per kg body weight per hour, at the first instance of plasma leakage from the intravascular compartment to the extravascular compartment. The process must continue till the difference between the upper and lower blood pressure is over 40 mmHg, or if the patient passes adequate urine. A patient can get further sick  if given a platelet transfusion when not required.

Risks of Platelet transfusion:

• Donor screening does not eliminate the risk of bacterial and other blood-borne infections
• Platelets are stored at room temperature, where bacteria can proliferate rapidly
• The incidence of bacterial contamination is higher for platelets than for red blood cells (RBC) (1 in 2000 for platelets versus 1 in 30,000 for RBC)
• Transfusion of any blood product, including platelets, can lead to transfusion-related acute lung injury
• Transfusion of any blood product may be associated with circulatory overload. Platelet transfusion introduces approximately 200 ml of intravascular volume per transfusion. The incidence of TACO is in the range of one to three per 100,000 transfusions and is higher in patients predisposed to volume overload (eg: with comorbidities such as congestive heart failure, renal failure, respiratory failure, and positive fluid balance).
• Platelets express Class I human leukocyte antigen (HLA) antigens, which can be recognised by the recipient's immune system as foreign. Production of anti-HLA antibodies can adversely affect the response to future platelet transfusions.
• Allergic reactions to platelet transfusion are relatively common. They are usually due to IgE directed against proteins in the donor plasma. Common symptoms include urticaria and pruritus in mild cases, and wheezing, shortness of breath and hypotension in more severe cases.
• Anaphylactic reactions (severe allergic reactions) are a very rare complication of platelet transfusion. These are associated with rapid onset of shock, angioedema, and respiratory distress. Many cases occur due to the production of anti-IgA antibodies in recipients who are IgA deficient.
• Febrile non-hemolytic transfusion reactions are mediated by various inflammatory mediators and leukocytes and may manifest as fevers, chills, and rigours.
• Transfusion-associated graft-versus-host disease (ta-GVHD) can occur with any transfusion that contains lymphocytes, given the correct immunologic setting.