At what platelet count after splenectomy should aspirin (acetylsalicylic acid) therapy be considered?

From the Guidelines

Aspirin therapy should be considered after splenectomy when platelet counts exceed 1,000/μL (1,000 × 10^9/L). Begin with low-dose aspirin (81-100 mg daily) as prophylaxis against thrombotic complications. This recommendation is based on the increased risk of thrombotic events that can occur with extreme thrombocytosis following splenectomy, as suggested by guidelines for managing myeloproliferative neoplasms 1. The spleen normally sequesters approximately one-third of the body's platelets, and its removal can lead to significantly elevated platelet counts. These elevated platelets may be more reactive and prone to forming inappropriate clots, particularly in the portal venous system or other vascular beds.

Some key points to consider when initiating aspirin therapy include:

• The risk and benefits of aspirin must be weighed based on the presence of vasomotor symptoms and the risk of bleeding, as noted in the management of essential thrombocythemia (ET) 1.
• Aspirin should be used with caution in patients with acquired von Willebrand disease (VWD) who have an increased risk of bleeding 1.
• Regular monitoring of platelet counts is essential after initiating aspirin therapy, as counts may continue to fluctuate in the post-splenectomy period.
• If platelet counts remain persistently above 1,500,000/μL despite aspirin therapy, consultation with a hematologist is warranted to consider additional cytoreductive therapies.
• Patients should be educated about symptoms of thrombosis (swelling, pain, redness in extremities) and instructed to seek immediate medical attention if these occur.

From the Research

Platelet Level Considerations for Aspirin Therapy after Splenectomy

• The decision to consider aspirin therapy after splenectomy depends on the platelet level, as extreme thrombocytosis can increase the risk of thrombotic events 2, 3, 4.
• Studies have shown that splenectomy can result in reactive thrombocytosis, with an incidence of approximately 75% to 82% 2, and a higher risk of thrombosis in patients with extreme thrombocytosis (>1000×10^9) 3.
• The use of aspirin as a preventive measure for venous thromboembolism (VTE) in patients with splenic trauma is still undefined 3, but a murine model study suggests that aspirin administration can mitigate platelet hyperaggregability after splenectomy 5.
• In terms of specific platelet levels, reactive thrombocytosis can range from mild (500,000-700,000/mm^3) to very severe (>1,000/mm^3) 4, and the use of low-dose hydroxyurea can reduce the platelet count to safe levels in patients with very severe thrombocytosis.
• However, not all studies support the use of platelet reduction therapy for treating postsplenectomy reactive thrombocytosis, as most patients recover without any therapy 6.

Aspirin Therapy Considerations

• Aspirin administration may be considered in patients with extreme thrombocytosis (>1000×10^9) after splenectomy, as it can mitigate platelet hyperaggregability and reduce the risk of thrombotic events 5.
• The optimal timing and dosage of aspirin therapy after splenectomy are still unclear and require further study 3, 5.
• Patients with hereditary spherocytosis who undergo splenectomy may be at higher risk of developing reactive thrombocytosis and thrombotic events, and may benefit from closer monitoring and consideration of aspirin therapy 4.