principles of crrt for aki - critical care canada of crrt for aki •principle: a fundamental,...
TRANSCRIPT
Objectives
• Review the principles of CRRT, relevant
to the practice of critical care
• Highlight work produced by the
“Toronto Acute Kidney Injury (TAKI) group”
• Principle: a fundamental, primary, or general law
or truth from which others are derived
Principles of CRRT for AKI
• Principle: a fundamental, primary, or general law
or truth from which others are derived
Principles of CRRT for AKI
• Principle: a fundamental, primary, or general law
or truth from which others are derived
Principles of CRRT for AKI
CRRT: - Truths
- Unknowns
Truths regarding CRRT for AKI
• It is commonly used for AKI in the ICU (BEST Kidney)1
• Suitable for use in hemodynamically unstable patients2
• Allows precise, adaptable, volume control
• Very effective control of uremia, PO4, K
• Available 24 hours a day
1. Int J Artif Organs. 2007;30:281-92.
2. BMC Nephrol. 2010 Nov 25;11:32.
Truths regarding CRRT for AKI
• It is commonly used for AKI in the ICU (BEST Kidney)
• Suitable for use in hemodynamically unstable patients.
• Allows precise, adaptable, volume control
• Very effective control of uremia, PO4, K
• Available 24 hours a day
• It is more expensive than other modalities of RRT
• Usually requires continuous anticoagulation
• Can cause severe depletion of electolytes (and
potentially other substances)
• Modes of CRRT
CVVHDdialysate
Truths regarding CRRT for AKI
13%
Intensive Care Med (2007) 33:1563–1570
Diffusion
• Modes of CRRT
CVVH (filtration)predilution replacement
ultrafiltrate
Truths regarding CRRT for AKI
1/2 of 53%
Intensive Care Med (2007) 33:1563–1570
Convection
• Modes of CRRT
replacement
ultrafiltrate
CVVH (filtration)postdilution
Truths regarding CRRT for AKI
1/2 of 53%
Intensive Care Med (2007) 33:1563–1570
Convection
• Hemodiafiltration
replacement
ultrafiltrate
CVVHDF
Truths regarding CRRT for AKI
dialysatecitrateCa
gluconate
34%
Intensive Care Med (2007) 33:1563–1570
Unknowns regarding CRRT for AKI
• Is it better than IHD or SLEDD ?
• When to initiate CRRT ?
• What mode to use – CVVHD or CVVH ?
• What dose of dialysis to use ?
Is it better than IHD or SLEDD?
IHD - mortality higher in some studies
- 5 RCT’s: no difference in mortality
- meta-analyses: no differences
SLED- safe, effective, cheaper than CRRT
- limited comparative data
When to initiate CRRT?
• Optimal timing unknown
• Heterogeneity across centres and physicians
• Early:• Avoid complications and organ damage ?
• Non-renal benefits ?
• Waiting for “traditional” indication:• Volume overload
• Metabolic acidosis
• Hyperkalemia
• Uremic complications
When to initiate CRRT?
• Observational study in 11 ICU’s in Canada
• 119 consecutive patients
Clark et al, Can J Anaesth 2012 59:861
When to initiate CRRT?• Survey of Nephrologists and Intensivists in Canada:
• Wide variation in the severity of indications and timing
Clark et al, Nephrol Dial Tranplant 2012 27:2761
When to initiate CRRT?
STARRT-AKI StudyRCT comparing:
• accelerated arm: CRRT within 12 hr
• standard arm - “traditional criteria”
• Inclusion criteria
AKI based on 2 out of 3 of:
• creatinine, oligura, NGAL
PI: Dr. Ron Wald
4 sites enrolling, 6 almost ready
What mode to use – CVVHD or CVVH?
• Hemodialysis and hemofiltration both “clean” the blood,
but the range of molecules removed is a little different
• Clearance of small molecules is similar
• Better clearance of medium sized molecules by filtration
• Potential benefit in septic patients in removing cytokines
• Mode selection varies significantly across the world
BEST Kidney investigators:
- survey of 54 ICUs in 23 countries
- 1006 patients on CRRT
Uchino et al, Intensive Care Med 2007; 33:1563Friedrich et al, Crit Care 2012; 16:R146
What mode to use – CVVHD or CVVH?
OMAKI study: Optimal mode of clearance in critically ill
patients with acute kidney injury
Wald et al. Crit Care 2012, online Oct 25th
• Multicentre pilot study of CVVH v CVVHD at 35 ml/kg
• 78 patients enrolled
• SOFA score decreased more rapidly in CCVH group,
due to decreased vasopressor requirements
• No difference in mortality
What mode to use – CVVHD or CVVH?
OMAKI study: Optimal mode of clearance in critically ill
patients with acute kidney injury
Wald et al. Crit Care 2012, online Oct 25th
What mode to use – CVVHD or CVVH?
Meta-analysis (Friedrich et al):
Friedrich et al, Crit Care 2012; 16:R146
• 19 RCTs met inclusion criteria
• 3 trials compared CVVHD with CVVH at
similar small molecule clearance dose.
• Other studies used CVVHDF or variation in
dosing
• No difference in outcome
• Hemofiltration may reduce filter life
What mode to use – CVVHD or CVVH?
Meta-analysis (Friedrich et al):
Friedrich et al, Crit Care 2012; 16:R146
What dose of dialysis to use ?
Dose
Clearance in terms of volume cleared per hour
eg. replacement fluid (or dialysate) at 2000ml/h
in 70kg patient = 2000/70 = 28 ml/kg/h
Some refinements:
- loss of efficiency with predilution
- volume of citrate anticoagulation
• 206 patients randomized
• 60% sepsis
• CVVH versus
CVVH + added D
Saudan et al, Kidney Int 2006; 70:1312
± 42 ml/kg
± 25 ml/kg
What dose of dialysis to use ?
- 200 ICU patients with acute renal failure• CVVHDF 20 v 35 ml/kg/hr
• No difference
Tolwani et al J Am Soc Nephrol 2008; 19:1233
What dose of dialysis to use ?
NIH ATN study:
– 1124 patients, multicentred• Intensified (35ml/kg, 6x/wk IHD) versus
• Standard (20ml/kg, 3x/wk IHD)
• No difference in mortality
Palevsky et al. N Engl J Med 2008; 359:7.
What dose of dialysis to use ?
RENAL study (Australia)
– 1508 patients, approx 50% sepsis
– Prescribed dose achieved: 84 – 88%
– CVVHDF, postdilution (1:1 dialysate:filtration)• Low intensity: 25 ml/kg/hr
• High intensity: 40 ml/kg/hr
– No difference in mortality
N Engl J Med 2009; 361:1627-1638.
What dose of dialysis to use ?
• 25ml/kg seems adequate
• Some criticisms/comments:
– Delayed initiation of RRT in Tolwani and ATN studies: 6 to 8 days; RENAL: 48-54 hr in ICU before randomisation
– No clear separation of dose delivered when combining CRRT and IHD dosing (ATN study)
– Majority (65%) enrolled after initial dialysis
– Dosing was not actually achieved in the ATN study
– Timing of the higher dose may be important
What dose of dialysis to use ?