Alternative Methods for Anticoagulation Monitoring in Pediatric Patients with Applicability to a Patient with Severe Hemophilia A and Circulating Inhibitor

Anticoagulation monitoring in pediatric patients can be problematic because of the immaturity of the coagulation system in this population. In addition, the hemodilution required to place a small patient on bypass can interfere with standard monitoring methods. In this institution, the Hemochron Jr. ACT (activated clotting time)+ assay has been the standard of care for anticoagulation monitoring since 1997. This assay, with a target ACT of 400 s for initiating bypass, was compared to both the Medtronic HMS system (N = 7) and the Hemochron HiTT assay (N = 6) in pediatric patients. All three assays were then employed to monitor a pediatric Hemophilia A patient (Factor VIII <1%) with high inhibitor titer. Both the HiTT clotting time and the HMS heparin level showed statistically significant correlation to the ACT+ (HiTT, N = 24, r = 0.761; HMS, N = 31, r = 0.818). An HMS target heparin level of 1.5 mg/kg and a HiTT target clotting time of 180 s were found to be clinically equivalent to the 400-s ACT+ as indicators of the need for additional heparin. When a 7-year-old male with severe hemophilia A and high inhibitor titer required tricuspid valve replacement, all three assays were used to ensure appropriate anticoagulation management. During bypass, this patient's ACT+ remained out of range (>1005 s). The HiTT was maintained at >180 s and the HMS heparin level at >1.5 mg/kg. Heparin was administered when any single parameter was below the cutoff value. The use of the combination of three distinct monitoring assays for this patient allowed the surgical team an added level of confidence that appropriate anticoagulation had been maintained.