Outcomes of Intermittent Hemodialysis in Critically Ill Patients With Acute Kidney Injury

Acute kidney injury (AKI) is common in critically ill patients and associated with high morbidity and mortality. Worldwide, 13.5% of patients in the intensive care unit (ICU) receive renal replacement therapy (RRT) for AKI. For such patients, 90-day survival is approximately 50%, and dialysis dependence at 90 days is roughly 21%.

Current modalities of RRT for AKI include conventional acute intermittent hemodialysis (IHD), multiple variations of continuous renal replacement therapy (CRRT), hybrid treatments (such as prolonged intermittent renal replacement therapy [PIRRT]), and high volume peritoneal dialysis. There are significant practice variations in the provision of PIRRT across institutions, with respect to prescription, technology, lack of standardization of the procedure, and delivery of therapy. As reviewed in a recent paper, clinical trials generally have demonstrated that PIRRT is not inferior to CRRT regarding patient outcomes and offers cost-effective RRT along with other advantages usually ascribed to IHD, such as early patient mobilization and decreased nursing time. Overall, PIRRT is less common than CRRT, the latter being prescribed in the United States and Europe by 20% to 30% of clinicians and to about 10% of patients. However, PIRRT is more common in the Asia-Pacific region: up to 25% of patients are treated with PIRRT in Australasia, Malaysia, and the Philippines.

In the recent global study on the epidemiology of AKI in patients admitted in the ICU, AKI occurred in 57.3% at day 1 of ICU stay, and RRT was needed in 23.5% of these AKI patients. The RRT procedures used were CRRT in 615 sessions (75.2%) and intermittent hemodialysis in 197 sessions (24.1%); peritoneal dialysis occurred in only six sessions (0.7%). In a recent multicenter randomized trial on timing of initiation of RRT in critically ill AKI patients, a total of 462 RRT modalities were applied; 47% of modalities were IHD, 32% with CRRT and in 21% both modalities were used.

Although acute IHD and CRRT are thus the two most-used modalities in the ICU, practice patterns vary regionally because of cost, reimbursement policies, resources of the healthcare institution, and the technical expertise of the physician and nursing staff. Recently, IHD has undergone resurgence through variants that provide slower fluid and solute removal over longer periods of time, resulting in improved hemodynamic stability and increased solute clearance. Other advantages of intermittent therapies are early patient mobilization and decreased nursing time. In this regard, because dialysate can be prepared in the hemodialysis unit, after which the 90-L container filled with dialysate can be transported easily, the GENIUS (Fresenius Medical Care AG, Bad Homburg, Germany) batch hemodialysis system is used frequently in the treatment of dialysis requiring AKI in ICU patients. Genius is a single-pass batch dialysis machine that combines the advantages of a simple operation (because of the uncomplicated technical design of a batch system) with highly efficient dialysis therapy. The technical features of the Genius dialysis machine are described in detail elsewhere.

This system can be used for conventional IHD and the PIRRT modalities. An important factor in the application of a given modality is whether the management of the AKI patient in the ICU is exclusively in the hands of the intensivist or is a combined management of intensivist and nephrologist. In the United States, where therapy prescription and delivery are managed primarily by nephrologists, IHD still is applied predominantly. In contrast, in Australia, CRRT is used most commonly and managed by intensivists. A recent survey in German ICUs revealed that selection of initial RRT modality in AKI is more dependent on the size, local structures, and education of the intensivists rather than on the patient needs, whereas in a more general European survey most of the intensivists were responsible for prescribing RRT (92.6 %). Half of the respondents reported using both IHD and CRRT, but only 10% preferred IHD over CRRT. The reasons for preferring CRRT were the perception of better hemodynamic stability, better therapeutic effect resulting from cytokine removal, and easier fluid balance control. However, no study has ever provided proof of a better outcome with CRRT versus IHD.

In many parts of the world, ICU nursing staff members deliver all modalities of acute RRT; in other countries, support from nephrology staff is required. As machinery platforms become more universal for CRRT and IHD, it is likely that ICU expertise in all modalities will grow, provided in-service education and support are adequate to develop and maintain technical skills. The Kidney Disease Improving Global Outcome (KDIGO) Clinical Practice Guideline for Acute Kidney Injury suggests that for the majority of critically ill AKI patients the available modalities of RRT are complementary, with the caveats that CRRT and PIRRT be used in hemodynamically unstable patients and that CRRT is preferred for patients with acute brain injury or other causes of increased intracranial pressure of generalized brain edema.

This chapter addresses the outcomes of conventional IHD in critically ill patients with AKI. For sake of clarity, the intermittent character of hemodialysis is considered only if the dialysis session is not longer than the “classic” 4 to 5 hours; the hybrid treatments (such as PIRRT) are discussed in other chapters of this book.