Objective       To study the plasma concentration of tranexamic acid (TA) during cardiopulmonary bypass in infants with tetralogy of Fallot (TOF).       Methods        Five TOF infants with body weight of (7.36±2.08) kg were given an slow intravenous injection of initial dose of TA (100 mg/kg

10 min) before thoracotomy

following by another 100 mg/kg TA before the initiation of cardiopulmonary bypass (CPB). The concentration of TA was measured in blood plasma using

1

H-NMR spectroscopy.       Results      Plasma TA concentration

s were (224.61±195.28) μg/mL before CPB (at 20 min after TA administration)

(509.58±181.57) μg/mL at 60 min after CPB initiation

and (243.95±32.30) μg/mL at the end of operation

respectively. The plasma TA concentration before CPB was not significantly different from that at 60 min after CPB initiation (P=0.052) and that at the end of operation (P=0.83)

but there was significant difference between plasma TA concentration at 60 min after CPB initiation and that at the end of operation (P=0.02).       Conclusion       A 100 mg/kg initial dose of TA followed by an infusion of 100 mg/kg before the initiation of CPB is sufficient enough to provide an effective plasma concentration

which is higher than 125 μg/mL for patients with high risk of bleeding

indicating the dose of TA can be decreased.