The patient was a 6-year-old boy of height 107.7 cm and weight 17.7 kg. He was born by scheduled Cesarean delivery after gestation of 38 weeks and 2 days, with weight 3026 g and height 45.5 cm, because his mother was after hysteromyctomy. At 1 day old, he was diagnosed with tetralogy of Fallot (TOF), and he received palliative surgery at another hospital at 6 weeks. At 1 year, more than 50% thrombocytopenia and upper extremity movement disorder appeared after catheterization, and he was diagnosed with HIT II because his functional assay was positive for HIT antibodies. Therefore, radical intracardiac repair with administration of argatroban was performed at the hospital. After this surgery, aortic regurgitation and residual defect of the ventricular septum were confirmed. Follow-up observation was performed for these symptoms, in addition to pulmonary stenosis and regurgitation, which were associated with TOF.
Based on a desire for treatment at our hospital, the patient underwent a cardiac catheter test, which showed progression of pulmonary valve insufficiency. Thus, reoperation was scheduled for aortic valvuloplasty, pulmonary valve replacement, and repair of ventricular septal defect. Anesthesia was performed with slow induction of sevoflurane and maintained with fentanyl and sevoflurane/midazolam. No abnormalities were found on the coagulation test and HIT antibody had become negative, but argatroban and nafamostat mesilate were used as anticoagulants because some reports suggest that HIT II can redevelop due to heparin re-administration [1]. During surgery, we measured Celite ACT and kaolin ACT, which do and do not reflect the effect of nafamostat mesilate, respectively (Fig. 1). Physiological saline was used for the blood pressure line. The blood samples were collected from the arterial pressure line placed in the radial artery, but from the blood supply circuit only during cardiopulmonary bypass, because blood in the blood supply circuit most reflects the activation of the coagulation system by the cardiopulmonary bypass circuit. Therefore, there may be slight differences in ACT measurement values depending on the sampling line.
After thoracotomy, a 5-mg argatroban bolus was administered and continuous argatroban was started at 12 mg/h, which was then decreased to 3 mg/h because the activated partial thromboplastin time (APTT) was 136.6 s. However, since kaolin ACT decreased from 352 to 217 s, the dose was increased again to 12 mg/h and bolus administration of 2.5 mg was added. After kaolin ACT reached 501 s and the patient was placed on cardiopulmonary bypass, continuous administration of nafamostat mesilate was started at 50 mg/h, concomitantly with argatroban. ACT was continuously prolonged, and Celite ACT and kaolin ACT were 1500 and 600 s, respectively, at 3.5 h before weaning from cardiopulmonary bypass. Therefore, administration of argatroban was discontinued after the dose was decreased by half. ACT continued to be prolonged, although with some shortening, and thus the dose of nafamostat mesilate was decreased to 30 mg/h until weaning from cardiopulmonary bypass. Upon weaning, Celite ACT and kaolin ACT were 533 and 399 s, respectively.
ACT decreased to ≤ 200 s (177 s) for the first time at 5 h and 1.5 h after discontinuation of argatroban and nafamostat mesilate, respectively. Operation and anesthesia times were 10 h 9 min and 11 h 36 min, respectively. Intraoperative hemorrhage was about 1000 ml, and 560 ml of red blood cells (RBCs), 520 ml of fresh frozen plasma (FFP), and 250 ml of platelet concentrate (PC) were transfused. There was no significant postoperative bleeding. Extubation was performed on the day after surgery and the patient was discharged on postoperative day 11.