F10 and complement factor I deficiency: We used anti-fXa rather than aPTT as the indicator of residual heparin activity, because chromogenic anti-fXa assay is an automated laboratory test, which is considered the gold standard to measure actual heparin concentrations.15,18–20 It is less influenced than aPTT by confounding factors, such as congenital or acquired coagulation factor deficiencies.19,21 Point-of-care testing devices using protamine titration of heparinised blood could also be used to detect residual heparin after protamine reversal.22 The HepconHMS device offers a whole blood heparin concentration test.