Monitoring of acetyl salicylic acid-induced platelet inhibition with impedance aggregometry in children with systemic-to-pulmonary shunts

Abstract

Shunt thrombosis after implantation of systemic-to-pulmonary shunts in paediatric patients is common. Acetyl salicylic acid is used for anti-thrombotic treatment; however, the effect is rarely monitored, although it is known that the response varies. The aim was to determine the effects of acetyl salicylic acid medication on platelet aggregation in children with systemic-to-pulmonary shunts. A total of 14 children – median age 12 days; ranging from 3 to 100 days – were included in a prospective observational longitudinal study. All children were treated with oral acetyl salicylic acid (3–5 milligrams per kilogram once daily) after shunt implantation. Acetyl salicylic acid-dependent platelet aggregation in whole blood was analysed with impedance aggregometry (Multiplate®) after addition of arachidonic acid. Analyses were carried out before the primary operation, before and 5 and 24 hours after the first acetyl salicylic acid dose, and after 3–6 months of treatment. The therapeutic range for acetyl salicylic acid was defined as a test result less than 60 units. Acetyl salicylic acid reduced the arachidonic acid-induced platelet aggregation in all but one patient. Of the patients, 93% were in the therapeutic range 5 hours after acetyl salicylic acid intake, 86% were in the range after 24 hours, and 64% after 3–6 months. Acetyl salicylic acid reduces platelet aggregation after shunt implantation in paediatric patients, but a considerable percentage of the children are outside the therapeutic range. Monitoring of platelet aggregation has the potential to improve anti-platelet treatment after shunt implantation by identifying children with impaired acetyl salicylic acid response.