Blog entry by Arif Khwaja

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by Arif Khwaja - Monday, 23 April 2012, 6:34 PM
Anyone in the world

The recently published KDIGO guidelines provide a welcome and timely synthesis of the evidence base to support the management of AKI.The guidelines focused on 4 key domains: i) AKI Definition, ii) Prevention and Treatment of AKI, iii) Contrast-induced AKI and iv) Dialysis Interventions for the treatment of AKI.

The full summary of clinical practice statements is available at www.kdigo.org but a key recommendation is that clinicians effectively adopt the previously published AKI Network definition and staging  of AKI as follows:

  • An increase in serum creatinine by ³0.3mg/dl (³26.5mmol/l) within 48 hours or an
  • Increase in serum creatinine to ³1.5 times baseline within the previous seven days or
  • Urine volume £0.5ml/kg/hours for 6 hours.

 

Stage

Serum Creatinine

Urine Output

1

1.5-1.9 times baseline

OR

³0.3mg/dl (³26.5mmol/l) increase

<0.5ml/kg/hour for 6-12 hours

2

2.0-2.9 times baseline

<0.5ml/kg/hour for ³12 hours

3

3 times baseline

OR

³4.0 mg/dl (³353.6mmol/l) increase

OR initiation of renal replacement therapy

OR in patients less than 18 years a decrease in eGFR <35mls/minute/1.73m2

<0.3ml/kg/hour for ³24 hours OR

Anuria ³12 hours

 

The rationale for the staging system comes from a plethora of studies showing that the risk of death and renal replacement therapy (RRT) increases with each stage. Furthermore evidence suggesting patients in whom AKI resolves are at increased risk of death, CKD and cardiovascular disease has prompted KDIGO to make an ungraded suggestion that all those with resolved AKI should be considered to be at increased risk of CKD and be managed as per the KDOQI guidelines for individuals at risk of CKD.  However whilst there is no doubt that standardising the definition and staging of AKI provides a clear framework for studying outcomes in both epidemiological and clinical research the bedside utility of the proposed classification and staging maybe be questioned by many 'real-world' practicing clinicians. In particular it is not clear how staging will alter immediate management and outcomes. As with the CKD classification sustem the danger is that an epidemiological tool gets imposed onto clinical practice without any evidence that the classification system per se can improve outcomes or can lead to specific interventions. Furthermore the evidence that monitoring people  with resolved AKI as being at risk of CKD can i) prevent the onset of CKD or ii) is cost-effective is not presented.

Many other recommendations are made most of which are eminently sensible/obvious (e.g. use vasopressors for those with shock) but a few caught my eye:

  1. recommended use of oral NAC in contrast nephropathy – despite v weak evidence, plus the fact that NAC has poor oral bioavailability and increases tubular secretion of creatinine
     
  2. that regional citrate be the anticoagulant of choice in CRRT unless the patient is shocked/has liver disease – of course these are the very patients that are most likely to be on CRRT and given the complexities of citrate use it’s a shame no practical protocol was provided…
     
  3. that dialysis dose be measured in AKI either by using Kt/V ( almost certainly meaningless in a catabolic patient with AKI) or the effluent flow rate in CRRT – again no evidence from the Veterans and Australasian studies that dose of RRT in AKI has any impact on survival.
     
  4. support the use of CRRT in haemodynamically unstable patients whilst this is routine practice in many places the meta-analyses indicate this again has no impact on patient outcomes… and as well all know CRRT is rarely continuous.
     
  5. The use of insulin to maintain glycaemic control despite the risks of hypoglycaemia.

 

As with previous KDIGO reviews, the clear message is that there is a lack of evidence (particularly, well-designed interventional outcome studies) to underpin much of our everyday clinical practice. Indeed only 14.8% of the recommendations were graded '1A' whilst 63.9% of the recommendations were level 2. Thus these are not prescriptive guidelines but provided nuanced guidance for the clinician. The KDIGO co-chairs bullishly argue that recommendations should be made even when the evidence is weak as clinicians often ask "what do the experts do?" – this may be true but as history tells us the track record of expert opinion in the absence of evidence can often be deeply flawed.

The recommendation that an empirical definition and staging system be used in the management of AKI will arouse controversy and debate. As yet no data has been presented to show that these tools in themselves can improve outcomes in AKI and many clinicians will be wary about implementing what is essentially a research-based diagnostic and staging system into the clinical arena in the absence of such data – as was the case in CKD........

References

  1. Chertow GM, Burdick E, Honour M, Bonventre JV, Bates DW: Acute kidney injury, mortality, length of stay, and costs in hospitalized patients. J Am Soc Nephrol 2005;16:3365-3370.
  2. Clinical practice Guidelines for Acute Kidney Injury 2012. http://www.kdigo.org/clinical_practice_guidelines/AKI.php
  3. Mehta RL, Kellum JA, Shah SV, Molitoris BA, Ronco C, Warnock DG, Levin A: Acute kidney injury network: Report of an initiative to improve outcomes in acute kidney injury. Crit Care 2007;11:R31.
  4. Rabindranath K, Adams J, Macleod AM, Muirhead N: Intermittent versus continuous renal replacement therapy for acute renal failure in adults. Cochrane Database Syst Rev 2007:CD003773.
  5. Palevsky PM, Zhang JH, O'Connor TZ, Chertow GM, Crowley ST, Choudhury D, Finkel K, Kellum JA, Paganini E, Schein RM, Smith MW, Swanson KM, Thompson BT, Vijayan A, Watnick S, Star RA, Peduzzi P: Intensity of renal support in critically ill patients with acute kidney injury. N Engl J Med 2008;359:7-20.
  6. lomo R, Cass A, Cole L, Finfer S, Gallagher M, Lo S, McArthur C, McGuinness S, Myburgh J, Norton R, Scheinkestel C, Su S: Intensity of continuous renal-replacement therapy in critically ill patients. N Engl J Med 2009;361:1627-1638.
[ Modified: Thursday, 1 January 1970, 1:00 AM ]