Continuous renal replacement therapies: Anticoagulation in the critically ill at high risk of bleeding

Background: The ongoing necessity for systemic heparinization is a well-known disadvantage of continuous renal replacement therapies (CRRT), and alternative methods of anticoagulation may be required. Our aim was to evaluate, in patients with a high risk of bleeding, the possibility of an acceptable filter life with non-anticoagulation CRRT and, in case of early filter failure, the efficacy and safety of bedside monitored regional anticoagulation with heparin and protamine. Methods: Fifty-nine patients underwent CRRT for acute renal failure (ARF) following cardiac surgery. Patients who fulfilled one of the following criteria were selected for non-anticoagulation CRRT: spontaneous bleeding, aPTT >45 sec, thrombocytopenia and recent surgery (<48 hr). Filter life <24 hr without anticoagulation was the cut-off point for starting the regional anticoagulation CRRT. Heparin was infused pre-filter and protamine post-filter at an initial ratio of 1 mg protamine: 100 IU heparin. The ratio was adjusted to achieve a patient aPTT <45 sec and a circuit aPTT >55 sec. Results: Twenty-two (37.3%) patients had been selected for non-anticoagulation. Of diem, 12 patients continued to receive non-anticoagulation (filter life: 38.3+/-30.5 hr) while 10 switched to regional anticoagulation (filter life: 38.6+/-25 hr). During regional anticoagulation no statistical difference was found between baseline aPTT (36.7+/-6.4 sec) and patient aPTT (41.5+/-12.6 sec) while circuit aPTT (77.7+/-43.3 sec) was significantly higher than patient aPTT (p<0.0001). The probabilities of the circuits remaining free from clotting after 24, 48 and 72 hr were: a) non-anticoagulation: 55.5%, 30.1% and 16.6%, b) regional anticoagulation: 76.2%, 39.6% and 19.8%. There was no rebound anticoagulation observed after regional anticoagulation CRRT ended. Conclusions: Non-anticoagulation CRRT allowed an adequate filter life in most patients with a high risk of bleeding for prolonged aPTT and/or thrombocytopenia. Despite concerns regarding the need for careful monitoring, regional anticoagulation with heparin and protamine can be considered as a safe and valid alternative when non-anticoagulation is unsuitable because of early filter failure.