Serum Creatinine Changes Associated with Critical Illness and Detection of Persistent Renal Dysfunction after AKI

Abstract

Background and objectives AKI is a risk factor for development or worsening of CKD. However, diagnosis of renal dysfunction by serum creatinine could be confounded by loss of muscle mass and creatinine generation after critical illness.Design, setting, participants, & measurements A retrospective, single center analysis of serum in patients surviving to hospital discharge with an intensive care unit admission of 5 or more days between 2009 and 2011 was performed.Results In total, 700 cases were identified, with a 66% incidence of AKI. In 241 patients without AKI, creatinine was significantly lower (P,0.001) at hospital discharge than admission (median, 0.61 versus 0.88 mg/dl; median decrease, 33%). In 160 patients with known baseline, discharge creatinine was significantly lower than baseline in all patients except those patients with severe AKI (Kidney Disease Improving Global Outcomes category 3), who had no significant difference. In a multivariable regression model, median duration of hospitalization was associated with a predicted 30% decrease (95% confidence interval, 8% to 45%) in creatinine from baseline in the absence of AKI; after allowing for this effect, AKI was associated with a 29% (95% confidence interval, 10% to 51%) increase in predicted hospital discharge creatinine. Using a similar model to exclude the confounding effect of prolonged major illness on creatinine, 148 of 700 patients (95% confidence interval, 143 to 161) would have eGFR,60 ml/min per 1.73 m 2 at hospital discharge compared with only 63 of 700 patients using eGFR based on unadjusted hospital creatinine (a 135% increase in potential CKD diagnoses; P,0.001).Conclusion Critical illness is associated with significant falls in serum creatinine that persist to hospital discharge, potentially causing inaccurate assessment of renal function at discharge, particularly in survivors of AKI. Prospective measurements of GFR and creatinine generation are required to confirm the significance of these findings.

Critically Ill Patients Requiring Acute Renal Replacement Therapy Are at an Increased Risk of Long-Term Renal Dysfunction, but Rarely Receive Specialist Nephrology Follow-Up

“…This means it is likely that estimates of creatinine generation, implicit in eGFR equations, are poorly calibrated to this group; eGFR could therefore significantly overestimate true GFR in many survivors of critical illness for a significant period after the acute illness [5]. The use of CKD-EPI eGFR in this study is pragmatic; it is a simple clinical tool used by clinicians to assess AKI recovery and, in the absence of measured GFR, gives a lower limit for the prevalence of CKD.…”

“…Importantly, the effects of prolonged major illness can confound serum creatinine-based assessment of CKD risk at hospital discharge [5]. To document clinical need and current practice in our region, we examined the rates of specialist follow-up and development or progression of CKD in patients who received RRT in the ICU over a one-year period.…”

Acute kidney disease and renal recovery: consensus report of the Acute Disease Quality Initiative (ADQI) 16 Workgroup

“…This approach has limitations, however, and loss of muscle mass, changes in volume of distribution, changes in renal reserve, and hyperfiltration can confound the assessment of functional recovery [54][55][56][57][58][59][60] . The limitations of using serum creatinine to assess recovery are supported by observational data indicating that AKI is associated with an increased risk of CKD, even when accompanied by an apparent complete return of serum creatinine to baseline levels 61,62 .…”

Promoting Kidney Function Recovery in Patients with AKI Requiring RRT

“…Moreover, recent studies highlight the inadequacies of serum creatinine as a marker of GFR and recovery in the critically ill, whereby the use of eGFR and serum creatinine overestimated kidney function recovery compared with measured creatinine clearance (37,38). The discrepancy may be explained by the effect of muscle mass loss associated with prolonged critical illness (27,28,38). Efforts to standardize definitions of kidney function recovery in AKI-D are ongoing and are a key consideration in future clinical trial design.…”