A feasible strategy for preventing blood clots in critically ill patients with acute kidney injury (FBI): study protocol for a randomized controlled trial

BACKGROUND: Previous pharmacokinetic trials suggested that 40 mg subcutaneous enoxaparin once daily provided inadequate thromboprophylaxis for intensive care unit patients. Critically ill patients with acute kidney injury are at increased risk of venous thromboembolism and yet are often excluded from these trials. We hypothesized that for critically ill patients with acute kidney injury receiving continuous renal replacement therapy, a dose of 1 mg/kg enoxaparin subcutaneously once daily would improve thromboprophylaxis without increasing the risk of bleeding. In addition, we seek to utilize urine output prior to discontinuing dialysis, and low neutrophil gelatinase-associated lipocalin in dialysis-free intervals, as markers of renal recovery. METHODS/DESIGN: In a multicenter, double-blind randomized controlled trial in progress at three intensive care units across Denmark, we randomly assign eligible critically ill adults with acute kidney injury into a treatment (1 mg/kg enoxaparin subcutaneously once daily) or control arm (40 mg enoxaparin subcutaneously once daily) upon commencement of continuous renal replacement therapy. We calculated that with 133 patients in each group, the study would have 80% power to show a 40% reduction in the relative risk of venous thromboembolism with 1 mg/kg enoxaparin, at a two-sided alpha level of 0.05. An interim analysis will be conducted after the first 67 patients have been included in each group. Enrolment began in March 2013, and will continue for two years. The primary outcome is the occurrence of venous thromboembolism. Secondary outcomes include anti-factor Xa activity, bleeding, heparin-induced thrombocytopenia, filter lifespan, length of stay, ventilator free days, and mortality. We will also monitor neutrophil gelatinase-associated lipocalin and urine volume to determine whether they can be used as prognostic factors for renal recovery. DISCUSSION: Critically ill unit patients with acute kidney injury present a particular challenge in the provision of thromboprophylaxis. This study hopes to add to the growing evidence that the existing recommendation of 40 mg enoxaparin is inadequate and that 1 mg/kg is both safe and effective for thromboprophylaxis. In addition, the study seeks to identify predictors of renal recovery allowing for the proper utilization of resources. TRIAL REGISTRATION: EU Clinical Trials Register: EudraCT number: 2012-004368-23, 25 September 2012.