Over the last decades, more than 35 different definitions have been used to describe acute kidney injury (AKI). Multiple definitions for AKI have obviously led to a great disparity in the reported incidence and mortality of AKI making it difficult or even impossible to compare the various published studies focusing on AKI. Therefore, it became crucial to establish a consensual and accurate definition of AKI that could desirably be used worldwide. Recent consensus criteria for AKI definition and classification [the Risk Injury Failure Loss of kidney function End-stage kidney disease (RIFLE) and the Acute Kidney Injury Network (AKIN) classifications] have led to more consistent estimates of its epidemiology. This review will present and critically discuss current literature about AKI diagnosis and epidemiology.

1. ACUTE KIDNEY INJURY IN CRITICALLY ILL
PATIENTS IN THE NEW MILLENIUM:
DEFINITION AND EPIDEMIOLOGY
JOSÉ ANTÓNIO LOPES, MD, PhD
Assistant Professor of Nephrology
Faculty of Medicine, University of Lisbon
Department of Nephrology and Renal Transplantation
Centro Hospitalar Lisboa Norte, EPE, Lisboa, Portugal
jalopes93@hotmail.com
Barcelona, 4th March 2014

2. DEFINITION AND CLASSIFICATION OF AKI
≠ DEFINITIONS
≠ INCIDENCE
≠ MORTALITY≠ MORTALITY

3. DEFINITION OF AKI
INCIDENCE AND MORTALITY
Chertow GM et al. J Am Soc Nephrol 2005
N=9.210

5. DEFINITION OF AKI
1. Easy to use
2. High sensitivity and specificity in ≠ settings
3. Consider variations in baseline SCr
4. Determine AKI severity
5. Identifiy early and late AKI

6. RIFLE Classification
Risk, Injury, Failure, Loss, End-stage kidney disease
Bellomo R et al. Crit Care 2004

7. Risk Injury Failure
Ricci Z et al. Kidney Int 2008
VALIDATION OF THE RIFLE IN THE ICU

8. RIFLE CLASSIFICATION
INCIDENCE AND STRATIFICATION OF AKI

9. Lopes JA et al. Clin Kidney J 2013




67%
36%
11%
36%
 18%

10. SAPS II RIFLE
AKI IN CRITICALLY ILL SEPTIC PATIENTS
Lopes JA et al. Crit Care 2007
0.778 0.750

11. Hoste E et al. Crit Care 2006
CRITICALLY ILL PATIENTS

12. Mehta RL et al. Crit Care 2007
AKIN CLASSIFICATION
Acute Kidney Injury Network

13. Chertow GM et al. J Am Soc Nephrol 2005
sCr ≥ 0.3 mg/dl -  IN-HOSPITAL MORTALITY
N=9.210

14. COMPARISON BETWEEN RIFLE
AND AKIN
INCIDENCE OF AKI AND PREDICTION OF
MORTALITY

15. Lopes JA et al. Crit Care 2008
P = 0.018
N=662

16. Lopes JA et al. Crit Care 2008
N=662

17. Acute kidney injury in critically ill patients classified by
AKIN versus RIFLE using the SAPS 3 database
Joannidis M et al. Intensive Care Med 2009
N=16.784

18. RIFLE
2004
AKIN
2009
LIMITATIONS STRENGTHS
KDIGO
2012

19. KDIGO Clinical Practice Guideline for AKI. Kidney Int 2012
KDIGO CLASSIFICATION

20. LIMITATIONS OF CLINICAL
CLASSIFICATIONS
URINE OUTPUT
Sensitivity and specificity
Hourly basis register (+++ ICU)
SCr
 variability in endogenous production and S release
Multiple factors can interfer with SCr determination
Hemodilution
Sepsis   production
CKD  late  in SCr
Marker of renal function and not of lesion

21. BIOMARKERS IN AKI
Murray PT et al. Kidney Int 2013

22. Coca SG et al. Kidney Int 2008
BIOMARKERS IN AKI

23. FRAMEWORK FOR EVALUATING AKI
BASED ON BIOMARKERS
Murray PT et al. Kidney Int 2013

24. BIOMARKERS IN AKI
FUTURE DIRECTIONS
 Confirm that the proposed expansion of the diagnostic criteria for AKI
to include the isolated presence of damage biomarkers, with
preserved function, is clinically relevant.
 Determine the mechanistic pathways that are involved in the
development of AKI and its natural course.
 Define the prognostic value of the combined use of functional and
damage markers in sequential measurements to confirm the
prognostic significance of these categories.
 Ascertain how well the combination of damage and functional markers
can improve recognition of AKI in the setting of CKD.
Murray PT et al. Kidney Int 2013

25. BIOMARKERS IN AKI
FUTURE DIRECTIONS
 Large population-based studies would be required across multiple
centers enrolling patients in the wide spectrum of AKI and different
disease states, to determine whether operationalizing the approach to
AKI with a simple 2x2 table to mechanistically define AKI cases and
their evolution usefully influences patient management and ultimately
improves outcomes.
 Discover and confirm the sensitivity and specificity of damage and
functional markers for specific situations.
 Establish standard techniques for collection, handling, and
presentation of biomarker data that permit appropriate interpretation
across settings.
Murray PT et al. Kidney Int 2013

26. EPIDEMIOLOGY OF AKI IN THE ICU
INCIDENCE
Bagshaw SM et al. Crit Care 2007
N=91.254

27. Lopes JA et al. Clin Kidney J 2013




67%
36%
11%
36%
INCIDENCE OF AKI IN THE ICU

28. Uchino S et al. JAMA 2005
EPIDEMIOLOGY OF AKI IN THE ICU
PATIENT CHARACTERISTICS AND RISK FACTORS
N=29.269

30. EPIDEMIOLOGY OF AKI IN THE ICU
SHORT- AND LONG-TERM OUTCOMES

31. Bagshaw SM et al. Nephrol Dial Transplant 2008
N=120.123
A multi-centre evaluation of the RIFLE criteria for
early acute kidney injury in critically ill patients

32. Long-term risk of mortality after acute kidney injury
in patients with sepsis: a contemporary analysis
Lopes JA et al. BMC Nephrol 2010
N=234

33. Bihorac A et al. Ann Surg 2009
N=10.518

34. Gammelager et al. Crit Care 2012
N=30.762

35. Bagshaw SM et al. Crit Care 2005
Prognosis for long-term survival and renal recovery in
critically ill patients with severe acute renal failure: a
population-based study

36. Hobson CE et al. Circulation 2009
N=2.973

37. Ishani A et al. J Am Soc Nephrol 2009
N= 233.803
Acute kidney injury increases risk of ESRD among elderly

38. Lai CF et al. Crit Care 2012
N=634

39. Ponte B et al. Nephrol Dial Transplant 2008

40. Hansen et al. Crit Care 2013
N=1.030

41. SEPSIS
HEMORRHAGE
FLUID OVERLOAD
ACUTE KIDNEY INJURY

42. • INFLAMMATION
• OXIDATIVE STRESS
• APOPTOSIS
Xiang Li et al. Curr Opin Crit Care 2010

43. SUMMARY
 The KDIGO work group has made the fusion of the RIFLE
and AKIN classifications in order to establish one
classification of AKI for practice, research, and public
health.
 The conceptual framework of functional and damage
biomarkers will need to be validated through future
studies, and additional evidence will be required to
establish their best combinations for utilization in clinical
practice.

44. SUMMARY
 AKI is an increasingly common complication in ICU
patients.
 Patients with AKI have higher ICU and in-hospital mortality
and longer lengths of stay, and AKI survivors are more
likely to be discharged to an extended care facility.
 Patients who survive AKI have a greater rate of long-term
mortality and other adverse outcomes (i.e. progression to
or acceleration of CKD and cardiovascular disease) than
patients who survive hospitalization without AKI.