Acute Kidney Injury

​Acute kidney Injury (AKI) refers to an abrupt decrease in kidney function. AKI is often the result of acute illness, infections, events that reduce kidney blood flow, medications, amongst other causes.  AKI complicates up to 20% of hospital admissions and many AKIs occur in the community outpatient setting.  

Patients who develop an AKI are at higher risk of developing chronic kidney disease, recurrent AKI, cardiovascular disease, hypertension, stroke, and mortality.  Strategies to prevent, recognize, and manage episodes of AKI are critical. Furthermore, follow up and management after episodes of AKI can improve patient outcomes and reduce future complications. 

About AKI


 
AKI is defined as any of the following: 
  • Increase in serum creatinine by ≥26.5 µmol/L) within 48 hours; or 
  • Increase in serum creatinine to ≥ 1.5 times baseline, which is known or presumed to have occurred within the prior 7 days; or  
  • Urine volume <0.5 ml/kg/h for 6 hours 
AKI staging is as follows: 
Kidney-Disease-Improving-Global-Outcomes-KDIGO-staging-classification-for-acute-kidney.png
Reference: KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney International Supplements (2012) 2,2 

There are circumstances where creatinine can be less accurate as a biomarker of kidney function, including extremes of muscle mass or with certain diets (e.g., very high or very low protein). Some medications can interfere with the excretion of creatinine (e.g., trimethoprim, fenofibrate). Cystatin C is an alternate marker than can used to estimate GFR in settings where creatinine may be less accurate. Cystatin C is not currently widely available in British Columbia.

KDIGO AKI guidelines are undergoing an update that will incorporate structural criteria defined by biomarkers of kidney injury. These biomarkers are not currently readily available for clinical use in BC (see link in Resources).​

 

Patients who survive an episode of AKI may have various levels of kidney function recovery. Patients who recover have higher risk of recurrent AKI, re-hospitalization, and death, and may subsequently develop long-term consequences such as chronic kidney disease (CKD) and/or cardiovascular disease (CVD).  “Acute kidney disease” is defined as abnormalities of kidney function and/or structure with implications for health for a duration of ≤3 months, while a duration of ≥3 months is classified as CKD.  

A risk tool was developed to estimate risk of advanced CKD after an episode an AKI. This model includes age, sex, AKI stage, pre-hospital serum creatinine, albuminuria, and discharge serum creatinine. 

See the risk too: https://qxmd.com/calculate/calculator_451/advanced-ckd-after-aki-risk-index 

(Reference: James MT, Pannu N, Hemmelgarn BR, et al. Derivation and External Validation of Prediction Models for Advanced Chronic Kidney Disease Following Acute Kidney Injury. JAMA. 2017;318(18):1787–1797. doi:10.1001/jama.2017.16326)

Outcomes-AKI.jpg

(Reference: Kellum, J., Prowle, J. Paradigms of acute kidney injury in the intensive care setting. Nat Rev Nephrol 14, 217–230 (2018). https://doi.org/10.1038/nrneph.2017.184 )

 

 
Recognizing episodes of AKI and ensuring patients who develop an AKI have adequate follow-up is important to detect early decline in kidney function and prevent further deleterious downstream effects. 

The essential components of discharge summary include: 
  1. Document AKI occurrence 
  2. AKI etiology 
  3. Baseline serum Cr 
  4. Peak serum Cr, kidney replacement therapy, or AKI severity 
  5. Discharge serum Cr 
  6. AKI-specific lab recommendations 
  7. AKI-specific medication recommendations 
  8. Follow up appointment with health care provider (e.g. PCP or nephrologist) 
  9. Recommendation for timing of follow up care 
Giles C, Novakovic M, Hopman W, et al. The Quality of Discharge Summaries After Acute Kidney Injury. Canadian Journal of Kidney Health and Disease. 2023;10. doi:10.1177/20543581231199018

Through our provincial initiative, a discharge communication template was developed.  
 

 

Medication adjustments are often required in the setting of AKI. In general, after AKI, renin-angiotensin-aldosterone system inhibitors (RAASi), sodium-glucose cotransporter-2 (SGLT-2 inhibitors), and mineralocorticoid receptor antagonists (MRA) should be restarted when steady-state renal function is achieved, if there are no contraindications. Not restarting guideline-indicated medications after AKI is associated with increased cardiovascular risk. (Reference: Brar S, Ye F, James MT, et al. Association of Angiotensin-Converting Enzyme Inhibitor or Angiotensin Receptor Blocker Use With Outcomes After Acute Kidney Injury. JAMA Intern Med. 2018;178(12):1681–1690. doi:10.1001/jamainternmed.2018.4749)

For any medication, consider how kidney function might affect its safety profile and if dose adjustments may be needed. Nephrotoxic medications such as non-steroidal anti-inflammatory drugs (ibuprofen, naproxen, diclofenac) should be avoided. 

The “Medication Guidance for Patients with Kidney Disease” document provides guidance surrounding medication management during and after AKI, as well as in the setting of chronic kidney disease. 

 
After hospital discharge, all patients should follow up with their primary care provider and have laboratory investigations to assess their kidney trajectory. In some cases, the admitting team may arrange patient follow up with a nephrologist or internist. Patients at greater risk of post-AKI complications should prompt earlier outpatient review. Risk factors include:  
  • Chronic kidney disease
  • Other cardiovascular risk factors: diabetes, hypertension, established cardiovascular disease 
  • Markers of vulnerability: recurrent AKI, cancer treatment, sepsis, critical care 
  • Markers of frailty: requiring help for basic/instrumental activities of daily living, dependent on personal care, ≥ 10 chronic conditions, dementia, low levels of physical activity, slow gait speed
  • Poor kidney recovery
High risk: 
  • Heart failure, or 
  • Poor kidney recovery (serum creatinine >50% above baseline), or 
  • Moderate recovery (serum creatinine >25% and <50% above baseline), with history of cardiovascular disease, critical care, cancer, recurrent AKI, or frailty 
  • Recommendation: Serum creatinine and outpatient follow up for clinical review/blood pressure assessment within 1-2 weeks of discharge if possible, and urine ACR 3 months post-discharge  
Moderate risk: 
  • Moderate recovery (serum creatinine >25% and <50% above baseline), or 
  • Good kidney recovery with history of cardiovascular disease, critical care, cancer,  recurrent AKI, or frailty 
  • Recommendation: Serum creatinine testing and outpatient follow up for clinical review/blood pressure assessment within 1 month of discharge, and urine ACR 3 months post-discharge 
Low risk: 
  • Good kidney recovery (serum creatinine ≤25% above baseline) and no significant risk factors for AKI complications 
  • Recommendation: Serum creatinine and urine ACR testing and outpatient follow-up for clinical review/blood pressure assessment within 3 months of discharge
Additional guidance on the timelines of post-discharge care for adults following AKI: https://bjgpopen.org/content/bjgpoa/early/2020/06/15/bjgpopen20X101054/F1.large.jpg?width=800&height=600&carousel=1

Calculator for Advanced CKD after AKI Risk Index: https://qxmd.com/calculate/calculator_451/advanced-ckd-after-aki-risk-index

 


Resources

General AKI and CKD Resources:

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