European journal of haematology
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Contact factor pathway deficiencies do not cause surgical bleeding but make heparin monitoring by the activated partial thromboplastin time (APTT) and activated clotting time (ACT) unreliable. Heparin monitoring during cardiopulmonary bypass (CPB) surgery in these patients is particularly challenging. Here we describe heparin monitoring during CPB using the chromogenic anti Xa assay in two patients with severe factor XII deficiency (FXII < 0.01 U/mL) and one patient with severe prekallikrein (PK) deficiency (PK < 0.01 U/mL). ⋯ We conclude that the sensitivity of APTT methods for contact pathway deficiencies is highly variable and although insensitivity is not a clinical problem in terms of bleeding, it can be a cause of discrepancy between different APTT reagents and the ACT. This can lead to confusion about a possible haemorrhagic tendency and delays in surgery. If these patients need to undergo cardiac surgery requiring high dose heparin treatment, monitoring by chromogenic anti Xa assay is a good alternative.