This past January, the Centers for Medicare & Medicaid Services began reimbursing for services provided to Medicare patients with acute kidney injury requiring dialysis (AKI-D). This represents a return to a financially sustainable approach to providing outpatient care for these patients after CMS removed the ability for hospitals to be reimbursed for payments to outpatient ESRD facilities for Medicare patients with AKI-D in 2012.1

Epidemiology

The incidence of AKI-D in hospitalized patients in the United States rose at a rate of 10% per year during the 2000s. The absolute number of patients with AKI-D more than doubled from 63,000 in 2000 to 164,000 in 2009.2 This growth in AKI-D, combined with high but declining inpatient mortality rates (~20-25% in more recent years),2-4 has led to an expanding population of AKI-D survivors. Existing studies have reported that up to one-third of AKI-D survivors remain dialysis-dependent at the time of hospital discharge.5-7

Clinical predictors of recovery of renal function

Once in the outpatient setting, survivors of AKI-D who remained dialysis-dependent at discharge may recover sufficient renal function to come off dialysis 20-60% of the time.5 In a recent publication from the Mayo Clinic, approximately a quarter of patients who survived in-hospital AKI-D transitioned off renal replacement therapy within six months, with the great majority of these recoveries (73%) occurring within the first three months.6

Outpatient recovery from AKI-D is influenced by patient comorbidities. Although half of patients without pre-existing CKD recovered within 6 months in the Mayo Clinic study, only 17% of patients with baseline CKD stages 3 to 4 recovered over the same period. Similarly, patients with heart failure were less likely to recover in the same study. Only 9% of patients with heart failure and a baseline eGFR of ≥ 30 ml/min/1.73 m2 recovered at 6 months compared to 49% of patients without heart failure and similar baseline renal function.4 Other predictors of renal non-recovery that have been implicated in existing literature include older age, diabetes, greater burden of comorbidities, and diagnosis of acute tubular necrosis (versus other etiologies of AKI).5, 7, 8

AKI-D and mortality

Patients with AKI-D are a small but vulnerable population with unique care needs. A recent study using University of Virginia health system data found that approximately 10% of patients who survive hospitalization from AKI-D die in the first 3 months after discharge, and patients with AKI-D who are unable to come off dialysis have a much higher mortality rate than those who recover.7 In a recent Taiwanese cohort, patients with AKI who recovered renal function had a 94% reduction in mortality compared to those who remained on dialysis.9

Potential interventions to promote renal recovery

Data are limited on identifying modifiable risk factors and potential interventions to promote renal recovery after surviving the index hospitalization with AKI-D. Strategies aiming to maintain adequate renal perfusion—such as avoidance of intradialytic hypotension—and to avoid additional renal insults (NSAIDs, CT contrast, infections, prolonged aminoglycosides) have been proposed to maximize the likelihood of renal recovery in outpatient AKI-D.

A recent study from the University of Michigan Health System found that among survivors of AKI-D who went on to require outpatient dialysis, those who recovered kidney function by 90 days after hospital discharge had suffered from fewer episodes of intradialytic hypotension and had lower net fluid removal and ultrafiltration rates during the first week of outpatient dialysis compared to those who did not recover kidney function.10 Experiencing ≥ 3 episodes of intradialytic hypotension (defined as SBP < 90 mmHg) was an independent predictor of renal non-recovery after multivariable adjustment.

  • Approaches to reducing intradialytic hypotension include:
  • Frequent blood pressure monitoring
  • Frequent dry weight assessment by nephrologist (and avoidance of standard “dry weight challenge” protocols)
  • Sequential ultrafiltration
  • Prescribing lower ultrafiltration rates or hourly total ultrafiltration limits
  • Dialysate cooling
  • Permitting higher pre-dialysis/ambulatory blood pressures
  • Use of peritoneal dialysis in AKI patients

Peritoneal dialysis is an intriguing strategy for promoting renal recovery in AKI-D given its well documented association with better preservation of residual renal function compared with hemodialysis in patients with ESRD.7 Unfortunately, studies of PD versus HD have not shown improved renal recovery or mortality rates in patients with AKI-D,8-9 and rapid facilitation toward outpatient PD following AKI-D may be a logistic challenge due to an infrastructure required, currently not in place in most areas of the country. CMS does include in its AKI rule that PD can be performed on an outpatient basis, but the patient must be treated in-center.

Outpatient dialysis center care process in AKI-D

Care coordination from the inpatient to outpatient setting is critical for patients with AKI-D, including medication reconciliation and attention to close follow-up with post hospitalization, labs, imaging, and health care appointments. An individualized approach to anemia and bone mineral disease management is warranted. Clear nephrologist communication with dialysis center staff and educating them on the unique needs of patients with AKI-D will allow for learning and continuous improvement in care. Given the higher acuity of patients with AKI-D, the current model of outpatient dialysis nephrologist visits likely requires some modification to adjust for the increased physician assessment needs of patients with AKI-D. Frequency and length of follow-up visits may vary dependent on the clinical and psychosocial stability of the patient and his/her circumstances.

Since the ultimate goal of outpatient AKI-D care is renal recovery, closely monitoring for the return of renal function is warranted. Nephrologists should recognize signs of improving renal function, including subjective measures such as reported urine output and sense of wellbeing and objective criteria such as declining interdialytic weight gains, improved serum creatinine, and increased renal function as measured by 24-hour urine creatinine or urea clearances. Recognition of ESRD is also important as it allows nephrologists to begin modality education, dialysis access planning, and renal transplant.

In order to provide optimal care, close collaboration between the nephrologist and the dialysis center staff is essential. The nephrologist should take a strong leadership role, since patients with AKI-D require individualized care, which is unlikely to be achieved through the maintenance dialysis routine care model.

The Quality Incentive Program and AKI-D

CMS has recently called for commentary on the inclusion of patients with AKI-D in the ESRD Quality Incentive Program (QIP). CMS does not currently collect data for any of the ESRD QIP measures in AKI-D but state that they will do so in the future and believe that monitoring this patient group is vitally important.

AKI-D is a fundamentally different disease state than end-stage renal disease, and CMS should be careful not to lump AKI-D and ESRD patients together. Patients with the two conditions are so clinically different that comparing them would be illogical. For instance, there is no evidence that existing ESRD clinical practice guidelines for anemia management, metabolic bone disease, vascular access management, dialysis adequacy, and nutrition are applicable to patients with AKI-D.

Similarly, potential measures most appropriate for patients with AKI-D may not be applicable to patients with ESRD. Monitoring recovery of patients with AKI-D and those progressing to ESRD may be valuable as reporting measures. Additionally, the frequency of provider visits (physician or extender) for outpatient AKI-D could act as a surrogate of vigilance in less easily measured treatment factors (such as tracking residual renal function and optimizing hemodynamic stability during HD).

All potential QIP measures for AKI-D should be first considered as reporting measures, given the limitations in knowledge surrounding optimal outpatient AKI-D management. Considering any measure as a clinical outcome measure with no data or experience would be ill-advised.

This issue is of added importance given the relatively small numbers of patients with AKI-D served by any individual outpatient dialysis center. Establishing acceptable measures in a small and heterogeneous population will likely prove challenging and requires close coordination between nephrologists, dialysis providers, and CMS. Furthermore, adding clinically meaningful quality measures for AKI-D must be counterbalanced with the concern of adding administrative burden by including these metrics.

Given the issues outlined above, CMS may be best served by convening a Technical Expert Panel (TEP) to discuss and develop measures that are appropriate for patients with AKI-D, that account for the low numbers of patients with AKI-D and their limited time on dialysis.

Conclusions

Recent changes in reimbursement have opened up outpatient dialysis services to a larger number of patients with AKI-D, allowing them to receive care closer to their homes. The number of patients requiring such care is relatively small but has been steadily increasing.

Post hospitalization care coordination and clear communication between nephrologists and center staff are important in this unique population. Recovery of renal function is the goal in the outpatient management of AKI-D and occurs in 20-60% of patients typically within the first 3 months of treatment but occasionally much farther out.

Practical strategies to promote and monitor for renal recovery include avoiding hypotension and nephrotoxins along with regular clinical follow-up and laboratory evaluation. Recognizing when patients can come off dialysis or have transitioned to ESRD are important clinical decision points.

Defining appropriate measures for the QIP in AKI-D is a challenging undertaking. Given the existing uncertainties in AKI-D CMS should strongly consider convening a TEP to discuss and develop measures appropriate for this vulnerable patient subgroup.

References

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  2. Hsu RK, McCulloch CE, Dudley RA, Lo LJ, Hsu CY. Temporal changes in incidence of dialysis-requiring AKI. J Am Soc Nephrol. 2013;24(1): 37-42.
  3. Xue J, Daniels F, Star R, et al. Incidence and mortality of acute renal failure in Medicare beneficiaries, 1992 to 2001. J Am Soc Nephrol. 2006;17(4): 1135-1142.
  4. Waikar S, Curhan G, Wald R, McCarthy E, Chertow G. Declining mortality in patients with acute renal failure, 1988 to 2002. J Am Soc Nephrol. 2006;17(4): 1143-1150.
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  9. Chen YM, Li WY, Wu VC, et al. Impact of weaning from acute dialytic therapy on outcomes of chronic kidney disease following urgent-start dialysis. PLoS One. 2015;10(4): e0123386.
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