KDIGO Clinical Practice Guideline for Acute Kidney Injury
When to discontinue RRT: Recommendations and Rationale

• 5.2.1: Discontinue RRT when it is no longer required, either because intrinsic kidney function has recovered to the point that it is adequate to meet patient needs, or because RRT is no longer consistent with the goals of care. (Not Graded)

Rationale

Many, but not all, patients requiring RRT will recover enough function not to require long-term RRT.^21,394,561 The mean duration of RRT in two recent large RCTs was 12–13 days.^562,563 Thus, daily assessment of both intrinsic kidney function and the ongoing appropriateness of RRT consistent with the goals of therapy for the patient are required. More than 50% of patients with severe AKI will not improve, despite appropriate therapy. The incidence of withdrawal of life-support treatments in critically ill patients with multiorgan failure has increased over the last decade.⁵⁶⁴ In addition to vasoactive medication, mechanical ventilation, and artificial nutrition, RRT is one of the therapies most likely to be discontinued during withdrawal of life support. In general, decisions to withdraw therapy occur in 10% of all patients from general ICUs, and are responsible for roughly 40% of all deaths. Analysis of a database of 383 AKI patients shows withdrawal of life support in 72% of deaths.⁵⁶⁵ In another single-center retrospective study involving 179 AKI patients requiring RRT, therapy was withheld or withdrawn in 21.2%.⁵⁶⁶ A posthoc analysis of the BEST KIDNEY database showed that CRRT was withdrawn in 13% of the patients, representing 29% of those who died while on CRRT and 21% of all nonsurvivors.¹⁹⁶

Assessment of kidney function during RRT is not easy and will depend on the modality used. In IHD, the fluctuations of solute levels prevent achieving a steady state and thus exclude the use of clearance measurements. Native kidney function can only be assessed during the interdialytic period by evaluating urine volume, urinary excretion of creatinine, and changes in SCr and/or BUN values. However, one must realize that intermittent treatment will be associated with post-treatment rebound in solute levels, and that changes in BUN and creatinine levels can also be modified by nonrenal factors, such as volume status and catabolic rate. In CRRT, continuous solute clearance of 25–35 ml/min will stabilize serum markers after 48 hours. This allows more reliable measurements of CrCl by the native kidneys during CRRT.

Very few investigators have looked at urine CrCl values as a guide for CRRT withdrawal. One small retrospective study (published as abstract) demonstrated that a CrCl (measured over 24 hours) > 15 ml/min was associated with successful termination of CRRT, defined as the absence of CRRT requirement for at least 14 days following cessation.⁵⁶⁷ Further prospective trials will be needed to support these findings. A large prospective observational study showed that, in 529 patients who survived the initial period of CRRT, 313 were successfully removed from RRT, whereas 216 patients needed ‘‘repeat CRRT’’ within 7 days of discontinuation. Multivariate logistic regression identified urine output as the most significant predictor of successful termination (OR 1.078 per 100 ml/d). Not surprisingly, the predictive ability of urine output was negatively affected by the use of diuretics.¹⁹⁶ Another retrospective observational analysis showed that, of a total of 304 patients with postoperative AKI requiring RRT (IHD), 31% could be weaned for more than 5 days and 21% were successfully weaned for at least 30 days. Independent predictors for restarting RRT within 30 days were longer duration of RRT, a higher Sequential Organ Failure Assessment score, oliguria, and age > 65 years.⁵⁶⁸ In other words, urine output seems to be a very important predictor of successful discontinuation of RRT. Whether too-early discontinuation of RRT, requiring reinstitution, is by itself harmful has not been properly investigated. The above-mentioned observational studies found a higher mortality in patients who needed to be retreated with RRT (42.7% vs. 28.5%¹⁹⁶ and 79.7% vs. 40%⁵⁶⁸). It is, however, not clear whether failure to wean is simply a marker of illness severity or contributed by itself to the adverse outcome.

The process of stopping RRT may consist of simple discontinuation of RRT, or may include a change in the modality, frequency, or duration of RRT. For example, switching from CRRT to IHD, or decreasing the frequency of IHD from daily to every other day, represents different methods of testing the ability of the patient’s own kidney to take over. No specific guidance can be provided for how to manage the transition of RRT from continuous to intermittent. Evidence from large observational studies suggests that large variation in practice exists.¹⁹⁶