When to Start RRT in AKI
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Transcript of When to Start RRT in AKI
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When to Start RRT in AKI
Alexander Usorov, MD2/24/09
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New Diagnostic Criteria for AKI
• Acute Dialysis Quality Initiative• Plus several Critical Care Societies• Equals Acute Kidney Injury Network or AKIN• The fundamental goal is to improve the
outcomes for patients who are at risk • The first AKIN conference was held in
Amsterdam in September 2005• Focused on the development of uniform
standards for definition and classification of AKI
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RIFLE-AKI
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Indications for RRT in AKI• Volume overload unresponsive to diuretics• Metabolic acidosis refractory to medical
management• Intoxication with dialyzable drug or toxin• Uremic symptoms
– Encephalopathy– Pericarditis– Uremic bleeding
• Progressive azotemia in the absence of specific symptoms
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Indications are open to interpretations
• How volume overloaded?• What should potassium level be?• How severe for metabolic acidosis?• What is the definition of diuretic
resistance?
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Dose and Modality
• VA/NIH trial vs Schiffl’s trial• Ronco• Mehta• Vinsonneau (Contniuous venouvenous
hemodiafiltration vs intermittent HD for ARF in pts with multiorgan dysfunction syndrome. Lancet 2006)
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Timing?• Less data available• Early literature (1950s-1960s) is significant for the
concept of prophylactic HD in AKI• Introduced by Dr. Paul E Teschan• Observational report using prophylactic HD in 15 pts with
oliguric ARF from Renal Center of the US Army Surgical Research Unit
• HD initiated prior to BUN reaching 200 mg/dL or uremic sxs
• Comparison was done to author’s past experience• Improvement in mortality, clinical course, uremic sxs
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Cont
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RCTs• Conger et al conducted a study on US Naval
Hospital Ship USS Sanctuary between April and October of 1970
• 18 patients with post-traumatic AKI– Intensive HD arm with pre-HD BUN<70 and SCr <5– Non-intensive regimen with delaying HD until BUN
approached 150 and SCr approached 10 or if clinically indicated
• Survival - 5/8 pts (64%) vs 2/10 (20%) pts • Major complications (Gram-neg. sepsis,
hemorrhage) were less freq in intensive arm
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Increased Mortality in Early HDIncreased Mortality in Early HD
• Gillum et al examined 34 pts at University of Colorado in 1986
• Pts were paired and randomly assigned once SCr reached 8– Intensive regimen with pre-HD BUN<60 and SCr <5– Less intensive regimen: BUN and SCr reached 100
mg/dL and 9 mg/dL• Average time from AKI to HD: 5+2 vs 7+3 days• Higher mortality in the intensive HD group
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Conventional wisdom
• In the absence of uremic symptoms, start hemodialysis if BUN is around 100 mg/dL
• No additional benefit seen with earlier HD initiation nor more intensive HD prescription
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Moving On
• Further studies focused mostly on the timing of initiation of CRRT
• Gettings et al published a retrospective analysis of 100 consecutive patients with post traumatic AKI in 1999
• Early vs late initiation based on BUN < or > 60 mg/dL at initiation of therapy
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Cont.
• Early group – CRRT initiated on hospital day 10+15– Mean BUN of 43+13
• Late group– CRRT initiated on HD 19+27– BUN of 94+28
• Survival – 39% in early vs 20% in late group
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• Critical points:– Non-randomized, retrospective– More pts with multisystem organ failure or
sepsis in late group– More pts oliguric on first day of CRRT in early
than late group, leading to suggestion that there was a confounding effect (?physician bias)
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More Retrospective Studies• Elahi et al reported a series of 64 consecutive patients
s/p cardiac surgery at a single UK center between January 2002 and January 2003
• In 28 pts, CVVHDF was started once BUN>84, SCr>2.8, or serum K>6, despite medical therapy and regardless of UOP
• Remaining 36 pts, CVVHDF was initiated when UOP was <100ml over 8 hrs despite Lasix
• Similar demographics and baseline clinical characteristics
• Surgery to renal support time was 2.6+2.2 days vs 0.8+0.2 days
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Limitations of the studies
• All recent studies are retrospective• Using BUN as a surrogate measure of AKI
duration is problematic• Urea generation varies from patient to
patient• Volume of distribution of urea in critically ill
patients is variable as well• Bias by indication
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How about a prospective study of CRRT timing?
• Bouman et al randomized 106 criticall ill patients with AKI to three groups:– Early high-volume CVVHDF (35 pts)– Early low-volume CVVHDF (35 pts)– Late low-volume CVVHDF (36 pts)
• Two early groups – txt started within 12 hrs of meeting inclusion criteria:– Oliguria x 6 hrs despite hemodynamic optimization– Measured cr clearance <20 ml/min on a 3-hr timed collection
• Late groups:– BUN>112– K>6.5– Pulmonary edema present
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Outcome
• No significant differences in survival were observed
• Critical point is that 28-day mortality was only 27%, much lower than in prvsly reported studies of critically ill patients with AKI
• Small sample size lead to low statistical power• Interestingly, 6/36 pts in late group never got
RRT (2 pts died and 4 pts recovered renal fxn)
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So When Do We Initiate RRT?
• Inadequate data available to answer this question
• Observational data suggests better outcomes are associated with early RRT initiation
• ? If “less sick” patients are included in these early groups
• Also, most pts with AKI are not treated with RRT
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