KDIGO Clinical Practice Guideline for Acute Kidney Injury
Complementary therapies in AKI patients: Recommendations and Rationale

• 5.6.1: Use continuous and intermittent RRT as complementary therapies in AKI patients. (Not Graded)

Rationale

Current modalities of RRT for AKI include IHD, CRRT, and PD. An overview of the different modalities of RRT and their commonly used settings is given in Table 21.

Since the introduction of CRRT into clinical practice in the early 1980 s, its use in critically ill patients with AKI has increased steadily.^710-712 The theoretical advantages of CRRT over IHD are the slower fluid removal, resulting in more hemodynamic stability and better control of fluid balance, the slower control of solute concentration, avoiding large fluctuations and fluid shifts (including a reduced risk [worsening] of cerebral edema), the great flexibility (allowing adaptation of the treatment to the patient’s need at any time), and the ability to perform the treatment with relatively simple and user-friendly machines (allowing ICU nurses to monitor the treatment). Disadvantages include the need for immobilization, the use of continuous anticoagulation, the risk of hypothermia and, in some settings, higher costs. Major advantages of IHD over CRRT are the fast removal of toxins and the restricted treatment period, allowing down-time for diagnostic and therapeutic interventions. IHD may, therefore, be the preferred treatment in patients where immediate removal of small solutes is required, such as severe hyperkalemia, some cases of poisoning, and tumor lysis syndrome. Hybrid treatments, such as SLED, may share some of the advantages of both IHD and CRRT without having their disadvantages (Table 22).

Several RCTs have compared CRRT to IHD in AKI patients. The most inclusive meta-analysis was performed by the Cochrane Collaboration, analyzing 15 RCTs in 1550 AKI patients. This analysis concluded that outcomes were similar in critically ill AKI patients treated with CRRT and IHD for hospital mortality (RR 1.01; 95% CI 0.92–1.12; n = 1245), ICU mortality (RR 1.06; 95% CI 0.90–1.26; n = 515), length of hospitalization (mean deviation -6.1; 95% CI -26.45 to -14.25; n = 25), and renal recovery (free of dialysis on discharge) in survivors (RR 0.99; 95% CI 0.92–1.07; n = 161).⁷¹³ Comparable results have been reported by other meta-analyses.^714,715 Individual studies used different definitions of AKI and were underpowered. Most of the trials excluded patients with hypotension or maximized efforts to improve the hemodynamic tolerance of IHD. The high rate of crossover between the treatment modalities also complicates the interpretation of the results. In addition, in some of the trials, IHD patients were treated with bioincompatible membranes and studies were not standardized for treatment dose. A subsequent RCT not included in the Cochrane metaanalyses reported similar outcomes.⁷¹⁶ Two recent studies, confined to single geographic regions, showed reduced costs with IHD compared to CRRT.^717,718 However, an analysis of cost ranges from a multicenter, multinational observational study found considerable heterogeneity in costs related to IHD and CRRT, and concluded that either therapy might be

Table 21 | Typical setting of different RRT modalities for AKI (for 70-kg patient)

CVVH, continuous venovenous hemofiltration; CVVHD, continuous venovenous hemodialysis, CVVHDF, continuous venovenous hemodialfiltration; IHD, intermittent hemodialysis; N/A, not applicable; PD, peritoneal dialysis; SCUF, slow continuous ultrafiltration; SLED, slow low-efficiency dialysis.

Table 22 | Theoretical advantages and disadvantages of CRRT, IHD, SLED, and PD

CRRT, continuous renal replacement therapy; IHD, intermittent hemodialysis; PD, peritoneal dialysis; SLED, sustained low-efficiency dialysis.

more or less costly depending on local practices, especially staffing.⁷¹⁹

Some large observational studies, including all patients receiving RRT, suggest that CRRT is an independent predictor of renal recovery among survivors.^720–722 This evidence, however, is insufficient to fully elucidate the impact of choice of therapy on this outcome. Appropriately planned prospective trials will be required to address this issue.

In conclusion, no RRT is ideal for all patients with AKI. Clinicians should be aware of the pros and cons of different RRTs, and tailor RRT on the basis of the individual and potentially changing needs of their patients. Besides the individual patient’s characteristics, the available expertise and resources may also be an important determinant of the ultimate choice.