A 55 year old with severe sepsis develops Heparin Induced Thrombotic Thrombocytopenia 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.
No Anticoagulant +/- Saline Flushes (50-100ml every hour)
* Ensure good wide bore access, high flow rates, consider predilution
Minimizes bleeding risk, but consumption of platelets and factors by membrane
Shortened filter life / increased time off dialysis
Provides good regional anticoagulation
Pre-mix solutions and protocols for use have simplified process
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
Prostacycline and Analogues
Reduced bleeding risk
Shorter filter life
Direct thrombin Inhibitors: Hirudin / Lepirudin / Argatroban
Linear relationship between levels and APTT (<100s) for Hirudin
Renal clearance, accumulation in renal failure (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
Serine Protease inhibitors (nafamostat)
limited experience, massive cost
Not readily available
Limited evidence supporting its use
Thus question would have benefited from a tabulated answer.
In the table below, I have included heparin, for completeness. However one would be well-advised to omit heparin from their answer in the exam.
If one were to review only one resource for this answer, one would be satisfied by this article from Tolwani and Wille.
(+/- regular saline flushes)
|High flow rate||
|Filtration fraction under 25%||
|Regional anticoagulation with heparin and protamine||
|Low molecular weight heparin||
|Platelet function inhibitors:
NSAIDs, aspirin, etc
|Direct thrombin inhibitors:
Hirudin / Lepirudin
Bivalirudin / Argatroban
|Xa inhibitors: Fondaparinux||
|Serine protease inhibitors: Nafamostat||
This table is reproduced with minimal changes in the Required Reading section on this topic.
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