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CRRT Anticoagulation in HIT — FRCA Final MCQ

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HardIntensive Care MedicineCRRT Anticoagulation in HITFRCA Final

A 62-year-old adult in ICU requires continuous venovenous haemofiltration for acute kidney injury. The circuit has clotted three times in 24 hours when run without anticoagulation. One year ago the patient had laboratory-confirmed heparin-induced thrombocytopenia; the platelet count has since been normal and a current HIT immunoassay is negative, consistent with remote HIT. There is no thrombosis, atrial fibrillation or other indication for systemic anticoagulation, and there is no active bleeding. Haemodynamics, liver function, lactate and acid–base status are normal. Which anticoagulation strategy for the extracorporeal circuit is most appropriate?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: E — Regional citrate anticoagulation with calcium replacement

Explanation lettering: E = shown as A · A = shown as B · B = shown as C · C = shown as E

C is correct. Citrate chelates ionised calcium in the extracorporeal circuit, suppressing calcium-dependent coagulation; systemic ionised calcium is maintained by calcium replacement. In remote, seronegative HIT, when CRRT requires anticoagulation only to maintain circuit patency and there is no separate indication for therapeutic anticoagulation, guidance favours regional citrate rather than heparin or a systemic non-heparin anticoagulant. A is inappropriate because UFH re-exposure is unnecessary and avoidable. B is also inferior: LMWH can cause HIT and its SmPC advises extreme caution even more than 100 days after HIT, after non-heparin alternatives have been considered. D is appropriate for acute HIT or another indication requiring systemic parenteral anticoagulation, but here adds bleeding risk and aPTT-guided monitoring without benefit. E is unsuitable because recurrent clotting is already reducing delivered therapy and wasting circuits. Randomised evidence shows citrate prolongs filter life and reduces bleeding compared with systemic heparin.

Reference: Cuker A, Arepally GM, Chong BH, et al. American Society of Hematology 2018 guidelines for management of venous thromboembolism: heparin-induced thrombocytopenia, Recommendations 6.1–6.2 (renal replacement therapy). Blood Advances 2018. https://pubmed.ncbi.nlm.nih.gov/33095849/