A 55-year-old patient with severe sepsis develops Heparin Induced Thrombotic 
Thrombocytopaenia Syndrome (HITTS) while on continuous veno-venous 
haemodiafiltration (CVVHDF). 

Outline the strategies available for prolonging the life of the CVVHDF circuit in this patient, mentioning the advantages and disadvantages of each strategy.

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College Answer

Ensure good wide bore access, high flow rates, consider predilution. 

No Anticoagulant +/- Saline Flushes (50 – 100 mL every hour) 

Advantage: 
 Minimizes bleeding risk. 

Disadvantage: 
 Shortened filter life / increased time off dialysis. 
 Alternative systemic anti-coagulant required for treatment of underlying HITTS. 

Regional citrate 
Advantage: 
 Provides good regional anticoagulation. 
 Pre-mix solutions and protocols for use have simplified process. 
Disadvantage: 
 Requires diligent monitoring of serum sodium, ionized calcium, and bicarbonate. 
 Requires infusion of calcium outside the circuit (access issues). 
 Large sodium load occurs when trisodium citrate used. 
 May cause alkalosis. 
 Special diasylate required: hyponatraemic, without buffer, Ca free. 
 Not appropriate in liver failure. 
 Alternative systemic anti-coagulant required for treatment of underlying HITTS. 

Prostacycline and Analogues 
Advantages 
 Reduced bleeding risk. 
Disadvantages 
 Shorter filter life. 
 Hypotension. 
 Alternative systemic anti-coagulant required for treatment of underlying HITTS. 

Direct thrombin Inhibitors: Bivalirudin / Hirudin / Lepirudin / Argatroban 
Advantages: 
 Linear relationship between levels and APTT (< 100s) for Hirudin. 
Disadvantages 
 Renal clearance, accumulation in renal failure (Bivalirudin, Hirudin, Lepirudin) Hepatic 
metabolism, accumulation in liver disease (Argatroban) No antagonist. 
 Argatroban falsely raises INR / PT. 
 Expense. 

Other agents 
Danaparoid 
 Limited availability 
 Risk of cross-reactivity with heparin-induced antibodies 
 Hard to monitor

 

Discussion

This question closely resembles several others. Past paper questions on this topic have included Question 4 from the second paper of 2010 and Question 17 from the first paper of 2007. The answer to such questions would benefit from a tabulated answer. A massive table, which acts as a reference for all such questions, can be found in the Required Reading summary on the Strategies to prolong the lifespan of the dialysis circuit

The major issue to remember in answering such questions is that all these fancy regional anticoagulant strategies do nothing about the need for systemic anticoagulation in HITTS.