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The Optimal Mode of Renal Replacement Therapy in Acute Kidney Injury (OMAKI) Study (OMAKI)

This study has been completed.
University of Toronto
Information provided by (Responsible Party):
Ron Wald, St. Michael's Hospital, Toronto Identifier:
First received: May 7, 2008
Last updated: March 9, 2012
Last verified: March 2012

Acute kidney injury (AKI) in the intensive care unit is common, devastating and costly. However, minimal evidence exists to guide the prescription of optimal renal replacement therapy (RRT). An important area of uncertainty surrounds the relative effects of convective versus diffusive modes of clearance. Although both clearance modes provide similar degrees of small molecule clearance, convective modes permit the enhanced clearance of larger-sized molecules which may mediate kidney and systemic toxicity in the setting of AKI.

Continuous renal replacement therapies (CRRTs) are frequently applied in critically ill patients with AKI. Convective clearance, as applied through continuous venovenous hemofiltration (CVVH) and diffusive clearance, as applied through continuous venovenous hemodialysis (CVVHD), may be readily compared in the context of patients receiving CRRT.

The purpose of this study is to examine the feasibility of conducting a larger study that will determine whether convective clearance (hemofiltration) confers improved outcomes as compared to diffusive clearance (hemodialysis) in patients with AKI.

Condition Intervention Phase
Acute Kidney Injury
Device: Continuous venvenous hemofiltration (CVVH)
Device: Continuous venovenous hemodialysis (CVVHD)
Phase 4

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Open Label
Primary Purpose: Treatment
Official Title: The Optimal Mode of Renal Replacement Therapy in Acute Kidney Injury (OMAKI) Study: A Pilot Randomized Controlled Trial of Convective Versus Diffusive Clearance

Further study details as provided by St. Michael's Hospital, Toronto:

Primary Outcome Measures:
  • We will study the feasibility of recruiting ther target population, administering the study therapies according to pre-defined protocols and following patients for clinical endpoints. [ Time Frame: 60 days ]

Secondary Outcome Measures:
  • Change in Sequential Organ Failure Assessment (SOFA) score. [ Time Frame: 7 days ]

Enrollment: 78
Study Start Date: May 2008
Study Completion Date: October 2010
Primary Completion Date: October 2010 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Experimental: 1
CVVH: Patients in this arm will receive CVVH at a replacement fluid rate of 35 mL/kg/h.
Device: Continuous venvenous hemofiltration (CVVH)
Continuous venovenous hemofiltration with a replacement fluid rate of 35 mL/kg/hr.
Active Comparator: 2
CVVHD: Patients in this arm will receive CVVHD at a dialysate flow rate of 35 mL/kg/h.
Device: Continuous venovenous hemodialysis (CVVHD)
Continuous venovenous hemodialysis at a dialysate flow rate of 35 mL/kg/hr.

Detailed Description:

The optimal mode of clearance in critically ill patients with acute kidney injury (AKI) who require renal replacement therapy (RRT) is unclear. Although both convection (as provided by hemofiltration) and diffusion (as provided by hemodialysis) provide equivalent removal of small-sized molecules, hemofiltration offers the potential for removal of large molecules many of which may be toxic. Hemofiltration and hemodialysis have never been compared in a rigorous randomized trial to date.

Continuous renal replacement therapies (CRRT) are widely used in the management of critically ill patients with AKI and current CRRT technology provides a practical platform on which to compare convective and diffusive clearance. We hypothesize that continuous venovenous hemofiltration (CVVH)- at identical doses of small molecule clearance that are provided by the comparison treatment of continuous venovenous hemodialysis (CVVHD)- leads to improved patient outcomes.

This study is an unblinded pilot RCT designed to test the feasibility of conducting a subsequent large scale study that will assess whether CVVH leads to improved patient outcomes (ie, survival, renal recovery) as compared to CVVHD. Although we will be collecting the full array of patient-relevant data for up to 60 days following randomization, the main purpose of this pilot study is to demonstrate the feasibility of recruiting, treating and following patients for a study designed to test this hypothesis.

Patient Population

The recruitment target for this study is 75 patients.

The inclusion and exclusion criteria are designed to enroll patients with AKI on the basis of presumed acute tubular necrosis who would ordinarily be candidates for continuous renal replacement therapies (CRRT) in Canada. The overall philosophy is to enroll and begin applying the study therapy as close as possible to the clinical need to start renal replacement therapy. Similarly, we would like to avoid enrolling patients whose risk of death is so high that the study therapy is unlikely to impact on the clinical outcome.


We will employ equivalent doses of hemofiltration (35 mL/kg/hr of replacement fluid) and hemodialysis (35 mL/kg/hr of dialysate).

Therapies will be administered using Primsaflex machines (Gambro Inc.) using regional citrate anticoagulation, heparin anticoagulation or no anticoagulation. Hospital-specific protocols for anticoagulation will be used. We have obtained Health Canada permission to utilize Prismocal, Normocarb, Hemosol BO and Prismasol 4 as infusates in patients receiving CVVH.


Ages Eligible for Study:   16 Years and older   (Child, Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  1. Adult patients (over 16 years of age) admitted to a participating ICU
  2. Serum creatinine increase of ≥ 50% from baseline
  3. Hemodynamic instability as defined by the cardiovascular component of the SOFA score of ≥ 1
  4. Attending physician deems the patient a candidate for RRT for at least one of the following reasons:

    1. Presence of oliguria, defined as a urine output of < 100 mL in the preceding 4 hours
    2. metabolic acidosis (HCO3- < 15 mmol/L and pH < 7.25)
    3. refractory hyperkalemia (K > 6.0 mmol/L)
    4. azotemia (BUN > 50 mmol/L)
    5. suspected uremic organ involvement (pericarditis, encephalopathy, neuropathy or myopathy)

Exclusion Criteria:

  1. renal replacement therapy within the previous 2 months
  2. presence of renal obstruction
  3. receipt of a kidney transplant in the previous year
  4. diagnosis of rapidly progressive glomerulonephritis, vasculitis, or acute interstitial nephritis
  5. indication for intermittent hemodialysis, specifically severe hyperkalemia, dialyzable drug or toxin
  6. terminal illness with associated life expectancy less than 2 months
  7. patients who are moribund
  8. prior enrollment in this study
  9. enrollment in a competing ICU interventional study
  10. no CRRT machine available
  11. acute renal replacement ongoing for > 36 hours
  Contacts and Locations
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Please refer to this study by its identifier: NCT00675818

Canada, Alberta
University of Alberta
Edmonton, Alberta, Canada
Canada, Ontario
London Health Sciences Centre
London, Ontario, Canada
Sunnybrook Health Sciences Centre
Toronto, Ontario, Canada, M4N 3M5
St. Michael's Hospital
Toronto, Ontario, Canada, M5B 1W8
Mt. Sinai Hospital
Toronto, Ontario, Canada, M5G 1X5
Sponsors and Collaborators
St. Michael's Hospital, Toronto
University of Toronto
Principal Investigator: Ron Wald, MDCM St. Michael's Hospital and University of Toronto
  More Information

Publications automatically indexed to this study by Identifier (NCT Number):
Responsible Party: Ron Wald, Staff Physician/Scientist, St. Michael's Hospital, Toronto Identifier: NCT00675818     History of Changes
Other Study ID Numbers: 07097
Study First Received: May 7, 2008
Last Updated: March 9, 2012

Keywords provided by St. Michael's Hospital, Toronto:
acute kidney injury
renal replacement therapy
critical care unit

Additional relevant MeSH terms:
Wounds and Injuries
Acute Kidney Injury
Renal Insufficiency
Kidney Diseases
Urologic Diseases processed this record on April 28, 2017