Extracorporeal renal replacement therapy in patients with heparin-induced thrombocytopenia

Introduction

Evaluation of renal replacement therapy (RRT) efficacy in heparin-induced thrombocytopenia (HIT) patients, using the alternative anticoagulant bivalirudin. A decreased platelet count (PC) is often seen after cardiopulmonary bypass with PC reduction by about 30% to 50%, correlating with the duration of cardiopulmonary bypass. However, only a few of these patients will develop HIT. Acute renal failure (ARF), followed by extracorporeal RRT, was seen in 90% of the patients with critical PC reduction found in the postoperative ICU. ARF has multiple etiology: baseline disorders (congestive heart failure, acute heart failure), hypoxemia, drugs used during surgery, and so on. The significance of postoperative thrombocytopenia, including HIT, urges to differentiate its causes and select appropriate patient care options, including use of alternative anticoagulants, namely bivalirudin. Bivalirudin (Angiomax™; The Medicines Company, Cambridge, MA, USA) is a synthetic hirudin analog, which reversibly binds thrombin. Bivalirudin is eliminated by enzymatic proteolysis (80%) and renal clearance (20%). The serum half-life is 25 minutes in patients with normal renal function, while it is longer in those with renal dysfunction (3.5 hours).

Methods

A retrospective study in HIT patients (clinical scoring and laboratory assays) who underwent RRT.

Results

Ten patients were studied, thereof four patients had low PC, thrombotic complications, RRT and prolonged duration of stay in the ICU – 17 days on average. Two of the patients had positive tests (ranged from 0.45 to 1.62) on postoperative days 6 to 8 and 11 to 12. All of the patients had their anticoagulant switched from heparin to bivalirudin, despite implanted circulation assisting devices and RRT. Coagulation system status was evaluated by the activated partial thromboplastin time, of which target value was twice the upper normal range. The bivalirudin infusion dose ranged from 50 μ/kg/hour to 100 μ/kg/hour, depending on the activated partial thromboplastin time value. Bivalirudin was found to be at least as safe and effective an anticoagulant as heparin.

Conclusion

HIT patients must be switched from heparin to alternative anticoagulant. Bivalirudin is a safe and effective anticoagulant for extracorporeal RRT; however, the dose should be adjusted individually. Bivalirudin has prolonged effect in ARF patients and does not have antagonists.