40 Years of Continuous Renal Replacement Therapy. Группа авторов

Recently, the Acute Dialysis Quality Initiative performed a consensus meeting focused on “Precision CRRT,” with one of the workgroups tasked with making recommendations on when to start CRRT [8]. The workgroup proposed that CRRT initiation should be individualized and not based solely on stages of AKI or kidney function, without broader consideration of the patient’s clinical context. Moreover, the workgroup articulated a conceptual model of a dynamic “demand-capacity” relationship for a patient’s given kidney function (Table 1). As such, the optional timing of initiation of CRRT could be considered when a patient is confronted with a mismatch in kidney capacity to manage ongoing metabolic and fluid demands (Fig. 1).

Table 1. Factors to consider while initiating CRRT (adapted from [8])

Perhaps in recognition that practice variation is itself a marker of suboptional quality of care, a recent pilot study described the implementation of a Standardized Clinical Assessment and Management Plan (SCAMP) algorithm to guide the initiation and discontinuation of RRT in critically ill patients with severe AKI [9]. The SCAMP algorithm was implemented in a single tertiary ICU setting in a practice shared by 9 nephrologists and it evaluated 176 patients over 13 months. The algorithm was completed daily in each patient with AKI in whom RRT would be reasonably considered and integrated tiered thresholds of physiological and biochemical indications for starting RRT. The algorithm further directed clinicians, when confronted by selected indications, to initiate RRT or not. In total, the SCAMP algorithm recommended starting RRT in 31% of completed forms for 176 critically ill patients with AKI. In 57% of these cases, clinicians deviated from the recommendation (i.e., did not start RRT), most commonly due to expected kidney recovery and futility. Alternatively, when the SCAMP algorithm recommended not starting RRT, compliance was 98%. Among patients whose clinicians adhered to the algorithm for starting RRT, hospital mortality was lower (42 vs. 63%, p < 0.01); however, this apparent mortality benefit was modified by patient baseline illness severity and predicted risk of death. The mortality benefit was evident only for those with a predicted hospital mortality <50% (i.e., less severely ill). The pilot study has numerous limitations (i.e., single-center, small, non-randomized, selection bias, confounding by indication, high non-adherence); however, it shows potential for quality improvement interventions, such as the implementation of a standardized algorithm, to contribute to improvements in the reliability of care and reduce suboptimal outcomes that may be partly attributable to variability in practice.

Fig. 1. Summary of the demand and capacity relationship – a conceptual model indicating as to when to initiate CRRT (reprinted with permission from ADQI [www.ADQI.org]).

      Why Start CRRT?

CRRT can achieve and maintain volume, electrolyte, acid-base, and uremic solute homeostasis among critically ill patients with AKI and multiorgan dysfunction. CRRT can facilitate additional therapeutic measures or reduce their potential for toxicity among patients who have poor tolerance due to AKI, such as provision of nutritional support, parenteral medications (including vital but nephrotoxic antimicrobials), blood transfusions, and other sources of “obligatory” fluid intake. CRRT can prevent overt complications of AKI. While CRRT can theoretically modulate inflammation and immune system function septic and other vasoplegic states, utilization of CRRT for this purpose remains uncertain. In the context of critical illness and multiorgan dysfunction, CRRT can provide an important platform to mitigate adverse kidney-organ (i.e., heart, lung, brain) interaction. Earlier CRRT initiation for these reasons is biologically plausible, clinically logical, and generally supported by observational data and small clinical trials (Table 2).

      Why Not Start CRRT?

CRRT can be associated with complications. CRRT necessitates central venous dialysis catheter insertion, exposure of blood to an extracorporeal circuit, and often use continuous anticoagulation to maintain circuit patency. CRRT, largely driven by ultrafiltration rate, has the potential to incite hemodynamic instability and contribute to delayed kidney recovery. CRRT also adds workload for bedside personnel, increases resource use, and is costly. As such, in the absence of high-quality data from rigorous clinical trials, there is a compelling argument for adopting a conservative approach for when to start CRRT. A number of clinical trials have not shown earlier that CRRT improves patients-centered outcomes when started in the absence of conventional indications or in response to AKI complications [7, 10, 11]. Accordingly, the theoretical and patient-specific benefit for earlier CRRT must be counterbalanced with the incremental resource implications and potential risk for delayed recovery or other complications related to CRRT (Table 2).

Table 2. Benefits and drawbacks of earlier RRT in the absence of conventional indications among critically ill patients with AKI (adapted from [22])

      Current Recommendations from Clinical Practice Guidelines

A number of organizations have published practice guidelines that include statements on the timing of initiation of RRT in ICU settings (Table 3). In 2012, the Kidney Disease Improving Global Outcomes (KDIGO) group made 2 statements regarding the timing of RRT initiation in AKI, both of which were based on expert opinion and not graded by evidence [4]. The first was a straightforward recommendation to initiate RRT “emergently when life-threatening changes in fluid, electrolyte, and acid-base balance exist.” The second statement asked clinicians to consider the “broader clinical context, the presence of conditions that can be modified with RRT, and trends of laboratory tests – rather than single BUN and creatinine thresholds alone – when making the decision to start RRT. Though the latter statement may be viewed as imprecise by suggesting clinicians use relatively subjective indications in their decision-making, this would appear a reasonable portrayal of current clinical practice. In 2013, the National Institute for Health and Care Excellence in the United Kingdom published statements similar to those proposed by KDIGO [12]. The National Institute for Health and Care Excellence guidelines also highlighted the paucity of high-quality evidence to guide clinician decision-making on this issue. The guidelines further emphasized that clinicians need better tools, such as clinical risk prediction scores or novel point-of-care tests as decision-support that may help identify patients with a higher likelihood of having worsening AKI and those who may benefit from the earlier initiation. In 2015, the French Intensive Care Society also published statements for use of RRT in ICU settings [13]. All of these guideline statements acknowledged the limitations in current evidence with each of them declaring that additional high-quality clinical