Abstract
Background Heparin-induced thrombocytopenia (HIT) in infants is a rare disorder, and the diagnosis
and management of HIT still remains challenging. Argatroban is a synthetic direct
thrombin inhibitor (DTI) that is widely used for treating HIT. However, little is
known about the efficacy of the activated clotting time (ACT) test in monitoring DTI
treatment as an alternative to the routinely used activated partial thromboplastin
time (aPTT).
Methods Between July 2013 and January 2015, four infants were diagnosed with HIT after surgical
correction of congenital anomalies. In all cases, heparin was used during cardiopulmonary
bypass (CPB). Diagnosis of HIT was based on the “4 Ts” pretest clinical scoring system,
and platelet factor 4 (PF4) antibody was detected using enzyme-linked immunosorbent
assay. Argatroban was used in treating HIT. When argatroban was infused, anticoagulation
tests (aPTT, prothrombin time [PT], thrombin time [TT], and fibrinogen) were performed
every 4 to 12 hours. ACT was used in addition to monitor the anticoagulation effect
of argatroban. The target ACT was 1.5 to 3.0 times the baseline. ACT was measured
every 2 to 4 hours and remeasured 1 hour after each dosage adjustment.
Results Thrombocytopenia (defined as a 50% decrease in platelet count) occurred during the
3rd to 6th day postoperatively. After the diagnosis of HIT, argatroban was started
immediately, and platelet counts stabilized and gradually increased. Anticoagulation
effect of argatroban was successful monitored by ACT and aPTT. Poor correlation between
the ACT test and aPTT test (R = 0.270, p = 0.092) was noted in one patient. ACT values increased rapidly after 3 to 7 days
on argatroban treatment. In most cases, low dosage of argatroban was given ranging
from 0.04 to 5.00 μg/kg/min.
Conclusion Argatroban may be an effective medicine in treating HIT in infants, in a reduced
dosage. The great fluctuation in argatroban dosage during the course of HIT treatment
necessitates close monitoring. ACT test may be reliable and convenient for monitoring
HIT treatment and may contribute to positive clinical outcomes in infants. The efficacy
of argatroban and the use of ACT monitoring in the management of HIT infants needs
further study.
Keywords
Infant - heart surgery - heparin - thrombocytopenia - argatroban - activated coagulation
time
