Erythropoietin in Acute Kidney Injury (EAKI): a pragmatic randomized clinical trial

At the beginning of the 90 s, following the release of the recombinant human erythropoietin (rhuEPO), transfusions' needs to treat anemia in chronic kidney disease patients were minimized [1]. This has been a revolutionary step in the management of renal anemia in chronic kidney disease and led to a major decrease in hepatitis B and C transmissions in dialysis [2]. However, using erythropoietin (EPO) to treat anemia in acute kidney injury (AKI) remains controversial.

AKI is a common disease with a global incidence estimated at 21% and tends to occur more frequently in the critical care setting [3]. The RIFLE and AKIN criteria for AKI definition were merged by the Kidney Disease Improving Global Outcomes (KDIGO) work group. AKI is defined as an increase in serum creatinine (SCr) ≥ 0.3 mg/dL (≥ 26.5 μmol/L) within 48 h or an increase in SCr to ≥ 1.5 times baseline within the last 7 days or a urine volume of < 0.5 mL/kg/h for 6 h [4]. Hales et al. reported that the majority of patients admitted with AKI have anemia (91%) [5]. The presence of anemia in their study was related to the oliguria and uremia level [5]. EPO is secreted by the tubulo-interstitial renal cells and it has been demonstrated that a chronic kidney injury would lead to a decrease in EPO secretion [6]. Some experiments have shown that EPO level usually increases within the first 48 h of AKI then drops progressively [7]. Transfusions will be needed if critically ill patients are hospitalized for a long period of time [8]. Transfusions may lead to sensitization and can hinder future transplantation in patients who reach end-stage renal disease. Therefore, it is essential to prevent transfusions in AKI patients.

We searched the literature for “recombinant human erythropoietin” or "erythropoietin" and “acute kidney disease” “acute renal failure” or or “acute kidney injury”. The search did not reveal any clinical trial assessing rHuEPO use in AKI. Throughout this paper, for a simplification purpose, we will use the term erythropoietin (EPO) instead of the recombinant human erythropoietin (rHuEPO). Based on the literature, some studies assessed the role of EPO before AKI occurrence to prevent kidney injury in cardiac surgery patients and contrast-induced nephropathy with conflicting results [9‐14]. Some experimental studies demonstrated a favorable effect of EPO and darbepoetin on the ischemic renal injury in rats [15, 16]. A metaanalysis of 10 randomized controlled trials where the majority of patients received a single dose of EPO concluded that EPO does not prevent AKI or dialysis or death [17]. Two recent clinical trials using high doses of EPO of 40,000 UI weekly following cardiac arrest and traumatic brain injury did not show any prevention of AKI and thus no protective renal effect [18, 19].

The role of EPO after the occurrence of AKI is not well studied. In 2005, a retrospective study showed that EPO treatment in acute renal failure patients did not lower the transfusion requirements, the renal recovery or patient survival [20]. However, it included many limitations such as the low dose of EPO used and the retrospective design [20, 21]. A recent clinical trial of children with hemolytic uremic syndrome showed a decrease in transfusion in patients receiving EPO but it included only 10 children [22]. Therefore, a clinical trial that studies the effect of EPO treatment in AKI patients with anemia is needed.

The primary objective of this randomized clinical trial was to compare the need of red blood cell transfusions in patients with AKI and anemia whether receiving or not rHuEPO. The secondary objectives were to compare the renal survival, the need for dialysis and patient death between the two groups.

This is the first randomized clinical trial that assesses the role of erythropoietin treatment in hospitalized patients with acute kidney injury and anemia. It showed no benefit towards the transfusion need or renal recovery or patient survival. This is aligned with the results of the retrospective study of Park et al. in 2005 that evaluated 187 patients including 71 patients who were administered erythropoietin three times weekly at a mean dose of 112 U/kg/week [20]. It was assumed that the retrospective design of that study and the low dose of erythropoietin prevented from showing any positive effect of erythropoietin on reducing transfusions in acute kidney injury patients. However, in our trial, erythropoietin was given at a median dose of 150 UI/kg for a median of 8–9 days and still was not beneficial. It remains unknown whether much higher doses can protect AKI patients from being transfused. A recent study on mice showed a U-shaped effect of EPO receptors on renal prognosis following acute kidney injury [23]. A high dose of 40,000 UI of EPO administered weekly was studied by Corwin et al. in 2002 and 2007 in critically ill patients admitted with anemia [24, 25]. Their patients had no AKI on admission but the goal of their study was to assess the possible reduction of transfusions with EPO [25]. In 2002, they found that patients treated with EPO had less need for transfusions but they had the same mortality rate as the control group [24]. In 2007, there was no significant difference in the transfusions between the group treated with EPO and the placebo [25]. Corwin et al. attributed this difference in the outcomes of the two trials to the TRICC trial that changed the practice in critical care units and decreased the transfusions' requirements until very low hemoglobin levels [25]. However, when Corwin et al. divided their sample to those admitted for trauma, who were in their 40 s, compared to those admitted for medical and surgical reasons, who were in their 60 s, EPO treatment was beneficial in the trauma group [25]. Our study included elderly patients in their 70 s and our results concur well with the elderly group of Corwin et al.

Another question that is worth studying in the future is whether concomitant iron administration could help maintain the hemoglobin level at acceptable ranges. Our patients had features of functional iron deficiency. In chronic kidney disease patients, functional iron deficiency is defined as TSAT levels < 20% and ferritin levels higher than 100 ng/mL [26]. These patients might benefit from intravenous iron. This was not included in the intervention of our trial and iron administration was left to the best practice of each physician, which led only to 20 to 33% of patients taking iron. In the trials of Corwin et al., 100% of patients received oral or parenteral iron over 29 days and this might explain the higher increase of hemoglobin in their patients [25].

An interesting finding in our study is the association of low hemoglobin levels at time of AKI diagnosis with the death outcome. The need for transfusion was also associated with the mortality. This association was statistically significant in patients who did not receive erythropoietin. Anemia has been associated with mortality in chronic kidney disease patients [27]. The combination of anemia and acute kidney injury was demonstrated as associated with increased mortality in several populations such as patients undergoing coronary artery bypass grafting surgery or patients with chronic heart failure [28, 29]. However, this association is not consistent in all studies and a retrospective cohort of 211 patients in 2013 did not find anemia as affecting the renal or the patient survival [30].

The C-Reactive protein level before death or discharge, the lack of renal recovery and the use of vasopressors were the most significantly associated factors with mortality in our AKI patients. Indeed, a lack of response to treatment, persistent inflammatory markers and hemodynamic instability in septic patients with AKI are the most prominent prognostic factors. This is in alignment with previous studies from different countries [31, 32]. A systematic review in 2013 of 154 large studies that evaluated the world incidence of AKI and associated mortality demonstrated a pooled AKI-associated mortality rates of 23.9% and that rate was declining over time [33]. The low rate of mortality in our group of patients not exceeding 15% can be due to the early diagnosis and management of AKI in this clinical trial setting.

Several lessons were learned during this trial. First, anemia is not as prevalent in acute kidney disease patients as previously reported [5]. It is true that we assessed 150 patients with AKI and anemia for eligibility but to reach this step of the process, we had to look at all AKI patients whether they had a hemoglobin less than 11 g/dL. We did not record the exact number of AKI patients admitted but we estimate that half of them did not have a low hemoglobin. Thus, the recruitment for this trial was very slow. This should be considered in future trials to include a higher number of centers to reach a higher number of patients. Second, we included in our study patients with AKI of all etiologies. Patients with pre-renal causes got in remission very quickly and this group of patients should probably not be included in future trials that are assessing erythropoietin treatment which effect takes time. Third, iron supplementation in AKI patients with anemia needs to be further studied whether with or without EPO taking into consideration the high rate of functional iron deficiency in this category of patients. Finally, as long as EPO trials in AKI or critical care setting are not showing benefits on mortality and as long as higher doses might cause thromboembolic complications, the end-point of these trials should focus more on patient-reported outcomes as discussed by Drüeke T. regarding ESA use in chronic kidney disease patients [34].