Platelet Transfusion in Dengue, DIC and ITP

Dengue, disseminated intravascular coagulation and immune thrombocytopenia all present with low platelet counts, but the mechanisms and the role of platelet transfusion differ. In each, a low count alone is not an indication. Platelets are given for bleeding or defined high risk situations, and the cause is treated.

Dengue. Thrombocytopenia is common, with a nadir around the critical phase. Bleeding in severe dengue is often internal, associated with prolonged shock, and platelet transfusion has not been shown to prevent bleeding. In endemic areas, including parts of the East African coast, dengue should be considered in febrile patients with falling platelets.

Disseminated intravascular coagulation. Consumption of platelets and clotting factors from systemic activation of coagulation, triggered by sepsis, obstetric complications, trauma, malignancy, severe malaria and transfusion reactions.

Immune thrombocytopenia. Autoimmune platelet destruction, with a low count and often mild bleeding. Platelet transfusion has a very short benefit because transfused platelets are destroyed.

Special groups. Pregnancy (obstetric causes of disseminated intravascular coagulation and gestational causes of thrombocytopenia), children, and older adults with comorbidity.

Dengue.

• Do not give prophylactic platelets for a low count alone, even when the count is under 10 x 10⁹/L, in a patient without bleeding.

• Platelets are considered for significant bleeding, usually with a count under 50 x 10⁹/L, together with red cells.

• Occult bleeding is suspected when haematocrit falls with persistent shock despite fluids. Red cells (or fresh whole blood where that is all that is available) are the product that treats this.

• Avoid excess fluid in the critical phase, and avoid injections and unnecessary procedures.

Disseminated intravascular coagulation.

• Treat the cause first.

• Platelets for active bleeding with a count under 50 x 10⁹/L, or for high risk of bleeding with a count under 20 x 10⁹/L, or before an invasive procedure.

• Plasma 10 to 15 mL/kg for bleeding with prolonged prothrombin time or activated partial thromboplastin time, and cryoprecipitate or fibrinogen concentrate for fibrinogen under 1.5 g/L with bleeding.

• No component replacement for abnormal results alone, when there is no bleeding and no planned procedure.

Immune thrombocytopenia.

• Platelets only for life-threatening or intracranial bleeding.

• First line treatment is corticosteroid, for example prednisolone about 1 mg/kg daily or dexamethasone 40 mg daily for 4 days, and intravenous immunoglobulin 0.8 to 1 g/kg as a single dose for rapid rise (repeat as needed).

• Thrombotic thrombocytopenic purpura (suspected with fever, anaemia with fragments, renal and neurological features) and heparin induced thrombocytopenia are managed with plasma exchange and drug withdrawal respectively, and platelets are avoided unless bleeding is life-threatening.

Red flags. Dengue: persistent vomiting, abdominal pain, mucosal bleeding, rising haematocrit, rapid fall in platelets, fluid accumulation. Disseminated intravascular coagulation: oozing from sites, haematuria and organ failure. Immune thrombocytopenia: intracranial or other severe bleeding.

Dengue.

1. Use red cells for blood loss and shock with falling haematocrit.

2. Platelets for significant bleeding at under 50 x 10⁹/L, one adult dose, reassessing.

3. Fluid management by phase, with careful monitoring.

Disseminated intravascular coagulation.

1. Treat sepsis, evacuate the uterus, control trauma, or treat the cause.

2. Replace platelets, plasma and fibrinogen for bleeding at the usual thresholds, directed by repeated counts and coagulation and, where available, viscoelastic tests.

3. Consider thromboprophylaxis when there is no bleeding.

Immune thrombocytopenia in life-threatening bleeding. Give a larger platelet dose (for example two adult doses), intravenous immunoglobulin, high dose corticosteroid and tranexamic acid, and arrange senior haematology input.

Special groups.

• Pregnancy: count for delivery over 50 x 10⁹/L for caesarean section, about 70 to 80 x 10⁹/L for neuraxial anaesthesia.

• Children: weight based dose of 10 to 20 mL/kg, and intravenous immunoglobulin 0.8 to 1 g/kg.

Monitoring. Platelet count, haematocrit, vital signs, urine output and bleeding. In disseminated intravascular coagulation, repeat counts, prothrombin time, activated partial thromboplastin time and fibrinogen every 6 to 12 hours when unstable, or sooner during bleeding.

Complications. Reactions, overload (especially in dengue with plasma leakage), thrombosis with unnecessary replacement in disseminated intravascular coagulation, and rapid platelet destruction in immune thrombocytopenia.

Referral and escalation. Intensive care for dengue shock and disseminated intravascular coagulation with organ failure, and haematology for refractory immune thrombocytopenia and suspected thrombotic microangiopathy.

Disposition. Discharge dengue patients when afebrile for 24 to 48 hours, haemodynamically stable and with a rising platelet count. Arrange follow up counts in immune thrombocytopenia.