Updates in Management and Timing of Dialysis in Acute Kidney Injury
Acute kidney injury (AKI) is a common complication in hospitalized patients and is associated with mortality, prolonged hospital length of stay, and increased healthcare costs. This paper reviews several areas of controversy in the identification and management of AKI. Serum creatinine and urine output are used to identify and stage AKI by severity. Although standardized definitions of AKI are used in research settings, these definitions do not account for individual patient factors or clinical context which are necessary components in the assessment of AKI. After treatment of reversible causes of AKI, patients with AKI should receive adequate volume resuscitation with crystalloid solutions. Balanced crystalloid solutions generally prevent severe hyperchloremia and could potentially reduce the risk of AKI, but additional studies are needed to demonstrate a clinical benefit. Intravenous albumin may be beneficial in patients with chronic liver disease either to prevent or attenuate the severity of AKI; otherwise, the use of albumin or other colloids (eg, hydroxyethyl starch) is not recommended. Diuretics should be used to treat volume overload, but they do not facilitate AKI recovery or reduce mortality. Nutrition consultation may be helpful to ensure that patients receive adequate, but not excessive, dietary protein intake, as the latter can lead to azotemia and electrolyte disturbances disproportionate to the patient’s kidney failure. The optimal timing of dialysis initiation in AKI remains controversial, with conflicting results from two randomized controlled trials.
© 2019 Society of Hospital Medicine
The Early vs Late Initiation of Renal Replacement Therapy in Critically Ill Patients with Acute Kidney Injury (ELAIN) was a prospective, single-center randomized trial in Germany of 231 critically ill, predominantly surgical ICU patients (about half postcardiac surgery) with at least KDIGO stage 2 AKI.44 Patients were randomized to early (within eight hours of developing KDIGO stage 2 AKI) or delayed (within 12 hours of developing KDIGO stage 3 AKI) RRT initiation; patients in the early RRT group initiated dialysis on average 20 hours earlier than the patients in the late group. All patients were treated with continuous venovenous hemodiafiltration. Early RRT initiation was associated with a 34% lower risk of mortality at 90 days, shorter hospital length of stay, and shorter RRT duration compared with delayed RRT initiation. There was no difference between groups in dialysis dependence at 90 days, but there was a lower risk of dialysis dependence at one year.46The Artificial Kidney Initiation in Kidney Injury Study (AKIKI)45 was a prospective, multicenter randomized trial in France that compared early versus delayed strategies of RRT initiation in 620 critically ill, mostly medical ICU patients with severe AKI (KDIGO stage 3). The median time between randomization and RRT initiation was two hours for the early and 57 hours for the delayed strategy groups. There were no differences between groups in length of hospital or ICU stay, vasopressor use, dialysis dependence, or 60-day survival. The early strategy group had a higher incidence of catheter-related bloodstream infections (10% vs 5%) and hypophosphatemia (22% vs 15%) compared with that of the delayed strategy group. Patients in the delayed strategy group regained normal urine output sooner than in the early strategy group. Approximately half of the patients in the delayed strategy group avoided RRT altogether. The authors of AKIKI concluded that there was no benefit to the early strategy of RRT in critically ill patients with severe AKI, and a delayed strategy of RRT initiation may avoid unnecessary RRT and reduce catheter-related infectious complications.
How can we interpret these discrepant results? Although ELAIN found a benefit to earlier RRT initiation in AKI, it has limited generalizability to medical ICU patients, who have higher mortality and whose outcomes might be less affected by dialysis timing. Patients in ELAIN had a high prevalence of congestive heart failure and CKD; it is possible that select patient populations may derive greater benefit from earlier RRT initiation. Although both ELAIN and AKIKI used the standardized criteria for RRT initiation, neither study could incorporate important clinical factors such as trajectory of kidney function, comorbid conditions, or symptoms, which play a significant role in the decision-making process in real-world clinical practice. Additional large-scale, multicenter trials are needed to guide the timing of RRT in critically ill patients with AKI. The Initiation of Dialysis Early Versus Delayed in the ICU (IDEAL-ICU)47 and Standard versus Accelerated Initiation of RRT in Acute Kidney Injury (STARRT-AKI)48 studies are currently underway and hope to provide clearer guidance regarding the optimal timing of RRT initiation in AKI (Table 4). Until further evidence is available, experts recommend taking into consideration the trajectory of kidney disease, concurrent organ dysfunction, and expected need for fluid and solute control when making decisions regarding RRT initiation in AKI.16
