Emergency Department Patients With Acute Kidney Injury: Appropriately Discharged but Inadequately Followed‐Up?

Acute kidney injury (AKI), defined according to increases in serum creatinine level or decreased urine output,1 is a frequent occurrence among hospitalized patients worldwide.2 In particular, a marked increase in AKI incidence has occurred in recent years in developed countries.2 Causes may include an aging population and a concurrent rise in the many comorbidities that are risk factors for AKI.3 These include hypertension, diabetes, cardiovascular disease, and chronic kidney disease (CKD).3 The epidemiology of AKI in hospitalized and critically ill populations has been well described but less is known about AKI in the emergency department (ED) patients that are subsequently discharged to be managed in the outpatient setting.4 Two recent studies from the nephrology literature that describe the epidemiology and outcomes of AKI patients discharged from the ED advance our understanding of this topic.5, 6 These studies have implications with respect to the disposition and follow-up of ED patients with AKI and are relevant to the practice of emergency medicine and nephrology. The first study, by Scheuermeyer et al.,6 was a retrospective cohort study that used administrative and laboratory databases to describe the characteristics and outcomes of patients who presented at two urban EDs with AKI over a 1-week period in 2014. Of 840 patients with at least one serum creatinine measurement, 90 patients (10.7%, 95% confidence interval [CI] = 8.7%–13.1%) had AKI as defined by a ≥50% increase in serum creatinine from baseline. When baseline creatinine values were unavailable, they were estimated according to current recommendations. As well, patients without a baseline serum creatinine but who had repeat testing within 48 hours and a subsequent increase of ≥0.3 mg/dL were also classified as having AKI. Overall, 5.5% of patients had AKI. Of the 31 (34.4%) AKI patients who were discharged home, only four (12.9%) had renal-specific follow-up from the ED. Renal-specific follow-up was defined as follow-up with a primary care physician, nephrologist, or urologist or recommending a repeat serum creatinine test, as identified by chart review. A larger study, focused specifically on renal follow-up of ED patients with AKI, was recently published in the Clinical Journal of the American Society of Nephrology.5 Using administrative data, Acedillo et al.5 reported the prevalence and outcomes of patients discharged home from the ED with a diagnosis of AKI based on changes in serum creatinine values. In this study, patients without a baseline serum creatinine level were excluded. Identification and severity of AKI was defined according to the Kidney Disease Improving Global Outcomes (KDIGO) AKI classification1 as detailed in Table 1. This retrospective cohort study included 6,346 AKI patients discharged from EDs in Southwestern Ontario (servicing a population of 1.6 million). Using propensity score matching, outcomes for AKI patients discharged from the ED were compared with two groups of otherwise similar patients: 1) those without AKI who were discharged home and 2) those with AKI who were admitted from the ED. 1.5 to 1.9 times baseline or ≥0.3 mg/dL increase ≥ 3.0 times baseline or Increase to ≥ 4.0 mg/dL or Initiation of renal replacement therapy <0.3 ml/kg/hr for ≥ 24 hours or Anuria for ≥ 12 hours Within 30 days following discharge, 149 AKI patients (2%) died, 22 (0.3%) required acute dialysis, and 1,032 (16%) were hospitalized. Among patients with stage 2 and 3 (moderate and severe) AKI, 5 and 16% died within 30 days, respectively. AKI patients who were discharged from the ED had a significantly lower rate of death at 30 days than those hospitalized with AKI (3% vs. 12%, RR = 0.3, 95% CI = 0.2–0.3). Those discharged with AKI had a higher rate of death within 30 days than those without AKI (2% vs. 1%, RR = 1.6, 95% CI = 1.2–2.0). These findings are generally reassuring: ED physicians appear to be appropriately triaging AKI patients for admission versus discharge home. Most of the patients discharged home with AKI in this study had only stage 1 AKI (95% of AKI patients overall) and this was associated with a small but significantly increased risk of subsequent complications and poor outcomes after discharge. An important caveat to this finding is that the extent to which any association between mild AKI and poor outcomes, including subsequent CKD, is causal remains unclear.7 The presence of AKI may largely reflect greater severity of underlying illness, as has been demonstrated in studies of patients with AKI after receiving iodinated contrast in the ED.8, 9 Nonetheless, at minimum, this finding serves as a reminder that AKI is a meaningful marker of severity of illness in the ED setting. As with Scheuermeyer et al., the study by Acedillo et al. showed that follow-up was likely inadequate in many cases. Only 68% of all patients discharged from the ED with AKI had subsequent follow-up within 30 days with a family physician, internist, nephrologist, or urologist. More importantly, only 28% of AKI patients discharged from the ED had a repeat serum creatinine test within 30 days. This suggests that, even for many of those who received some outpatient follow-up, there was inadequate assessment of whether AKI had resolved. The authors argue that it is possible that many cases of AKI, particularly if they were mild, were either unrecognized in the ED or not felt to be of clinical significance.5 Conversely, they may not have been recognized or felt to be of clinical significance by the outpatient physician responsible for follow up. Another possibility is that there were patient-level or systemic barriers to repeat outpatient creatinine testing after AKI. Whether repeat serum creatinine testing in all discharged AKI patients would improve patient outcomes is unclear given the marginally increased risk of death among this group relative to non-AKI patients. Nonetheless, given the high frequency with which AKI is present in patients discharged from the ED, even a modest effect on mortality could result in a meaningful number of deaths prevented. Ensuring “renal-focused” outpatient follow-up has been proposed as a way to improve outcomes following hospitalizations with AKI.10 The provision of post-AKI care in this context may help to identify evolution to CKD or potentially reversible causes of worsening AKI after discharge. A study using a U.S. Veterans Affairs database by Siew et al.11 demonstrated that after hospitalization with AKI, less than 10% of patients were seen in follow-up by a nephrologist prior to death, dialysis initiation, or an improvement in renal function to an estimated glomerular filtration rate of ≥60 mL/min/1.73 m2. In a large Ontario administrative database study, Harel et al.12 showed that after hospitalization with AKI, 41% of patients were seen for an outpatient nephrology assessment within 90 days of discharge. Those who had previously seen a nephrologist or were known to have CKD were most likely to receive such follow-up. Notably, after adjustment for baseline risk factors, those who received nephrology follow-up had a 24% lower mortality risk at 2 years compared to those that did not receive such follow-up. While it is unclear how follow-up by a nephrologist might be superior to follow-up by a family physician or internist, this study suggests that a follow-up assessment that includes a renal-focus can improve outcomes after AKI. Essential to any renal-focused assessment after a visit to the ED is a repeat measure of serum creatinine to assess for stability, resolution, or worsening of kidney function. KDIGO guidelines include an ungraded recommendation that patients be evaluated 3 months after AKI for resolution, new onset, or worsening of preexisting CKD. However, according to the severity or presumed etiology of the AKI, follow-up may be required sooner than 3 months. The findings by Acedillo et al., demonstrating a separation in outcomes between those discharged with and without AKI at only 30 days (and who predominantly had only stage 1 AKI), suggests that a shorter time frame for repeat creatinine testing is warranted regardless of AKI severity. Ensuring adequate and timely follow-up for AKI patients after discharge from the ED requires coordination between ED physicians, nephrologists, urologists, and family physicians. The provision of rapid-access nephrology and urology clinics for selected patients is one potential avenue for improving the care of such patients.10 In most cases, however, ensuring that patients have short-term follow-up with a primary care provider (and repeat serum creatinine testing) is likely to be adequate. As demonstrated in a 2010 study at a single large academic center, referrals sent at the time of the ED discharge to internal medicine, cardiology, and neurology clinics were ultimately completed by only 76.4% of patients.13 Factors accounting for noncompletion of referrals included “patient decision, inadequate or poorly understood discharge information, and systemic factors.”13 It is important to note that the likelihood of follow-up occurring (and consequently, the occurrence of other postdischarge outcomes) is likely to be affected by availability of primary care follow-up in general. As such, it must be noted that both the Acedillo et al. and Scheurmeyer et al. studies were performed in Canada where health care insurance is universal and primary care coverage may be more readily available than in other jurisdictions.14 Inadequate follow-up after AKI can also occur if the diagnosis is missed or not felt to be of clinical significance in the ED or by the outpatient physician responsible for follow-up. The findings of the study by Acedillo et al., in which patients discharged from the ED with AKI still experienced a significantly increased risk of adverse events, suggest that even mild AKI needs to be considered to have clinical significance. Such patients may warrant renal-focused management and follow-up. The extent to which “missed” AKI is an issue in the ED cannot be assessed on the basis of the studies by Acedillo et al. and Scheuermeyer et al. Regardless, the association between small increases in serum creatinine and adverse outcomes has previously been reported in various populations of hospitalized patients.2 Some experts have proposed automated serum creatinine based electronic alerts to ensure recognition of AKI and subsequent renal-focused management in the ED.15 In a randomized controlled trial of hospitalized patients, such automated AKI alerts were not shown to improve patient outcomes.16 Subsequent studies have suggested that linking electronic AKI alerts to an AKI-focused care bundle can improve outcomes17-19 particularly if done within the first 24 hours of diagnosis.18 These care bundles focused on strategies to: evaluate the cause of AKI (e.g., ensure obstructive uropathy has been ruled out); ensure adequate volume repletion; prevent initiation or continuation of nephrotoxic agents (e.g., nonsteroidal anti-inflammatory drug, angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers) and to avoid unnecessary radiocontrast exposure. To our knowledge, there are no studies assessing the implementation of AKI care bundles in the ED but we believe that this warrants future study. Automated alerts, sent to primary care providers (and/or specialists charged with follow-up), when patients with AKI are discharged from the ED, could help ensure adequate renal-focused follow-up with repeat serum creatinine testing. In conclusion, recent studies of AKI patients discharged from the ED suggest that, generally, ED physicians are performing the difficult task of triaging patients with AKI for admission or discharge appropriately. As has been shown in other settings,1 even mild AKI (defined as a small increase in serum creatinine from baseline per KDIGO guidelines1) is associated with a small but significantly increased risk of death or the need for dialysis following discharge. Ensuring renal-focused follow-up after discharge from the ED with AKI might improve outcomes for these higher-risk patients. Automated AKI alerts, linked to AKI-focused care bundles, hold promise for improving the management of AKI patients in the ED as well as for ensuring that AKI is adequately detected and appropriately followed up after discharge.

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