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Different doses of ultrafiltration in continuous veno-venous haemofiltration

 

For every 6 patients treated with high volume of ultrafiltration replacement of at least 35ml/kg/hr versus conventional 20ml/kg/hr one life will be saved.

Level of Evidence: 1+ (RCT with a low risk of bias)

 

Citation/s:Effects of different doses in continuous veno-venous haemofiltration on outcomes of acute renal failure: a prospective randomised trial. Lancet 2000 Vol 356 (9223) 26-30

 

Lead author's name and email: Claudio RONCO. Renal Research Institute, 207 East 94th Street, Suite 303, New York. NY 10128 USA. (cronco@rriny.com)

 

Three-part Clinical Question:

Patients: Critically ill patients with acute renal failure.

Intervention: CVVHF 20 or 30 or 45 ml/kg/hr ultrafiltration.

Outcome: Mortality.

 

Search Terms: Acute renal failure (13233), Haemofiltration (615) combined and limited to RCT (16). Limit to author Ronco C (2)

 

The Study: Non-blinded randomised controlled trial with intention-to-treat.

 

The Study Patients: Critically ill patients with acute renal failure (urine output 200ml/day despite fluid resus with PAFC monitoring and 500mg frusemide AND abnormal urea & creatinine concentrations) 75% were post surgical and 12.2% had a diagnosis of sepsis.


Control group (N = 146; 146 analysed): Standard ICU care with ultrafiltration of 20ml/kg/hr .


Experimental group (N = 279; 279 analysed): Two different 'high' volume replacement doses - 35ml/kg/hr and 45ml/kg/hr.

 

The Evidence:

 

Outcome

Time to Outcome

CER

EER

RRR

ARR

NNT

Mortality

15 days post RRT stop

0.589

0.427

28%

0.162

6

95% Confidence Intervals:

11% to 44%

0.063 to 0.261

4 to 16

 

·        There was no difference in the mortality between the two 'high' volume groups (35 & 45ml/kg/hr) (p = 0.87)

·        All patients in all three groups acheived >85% of the prescribed dose of ultrafiltration.

·        Survivors in all groups had lower initial blood urea levels.

·        >90% of all survivors had full recovery of renal function 15 days after stopping RRT.

 

EBM Questions: 

1.      Do the methods allow accurate testing of the hypothesis? Yes

 

2.      Do the statistical tests correctly test the results to allow differentiation of statistically significant results? Yes

 

3.      Are conclusions valid in light of the results? Yes. (Higher volume CVVHF is more effective than low volume)

 

4.      Did results get omitted, and why? No – all accounted for

 

5.      Did they suggest areas of further research? No not specifically

 

6.      Did they make any recommendations based on the results and were they appropriate? Yes. The authors state that all CVVHF should be prescribed at a ‘high’ dose of 35ml/kg/hr – there was no difference between this dose and 45ml/kg/hr. They also stated that pre-dilution might reduce the efficiency of filtration & therefore should be discouraged.

 

7.      Is the study relevant to my clinical practice? Yes. Acute renal failure is prevalent in ICU patients and most units use some form of continuous replacement therapy. As far as we are aware most units are using a dose close to this recommendation but accurate weighing and therefore dosing may be lacking in our practice.

 

8.      What level of evidence does this study represent?  1+

 

9.      What grade of recommendation can I make on this result alone? Grade B

 

  1. What grade of recommendation can I make when this study is considered along with other available evidence? N/A Extensive internet search yielded no similar studies.

 

  1. Should I change my practice because of these results? Yes – even though the general practice appears to be to prescribe 2l/hr (which is close to an ‘average’ patient of 70kg) we should ensure that patients are gaining 35ml/kg/hr. This study achieved >85% of prescription in all their patients which is impressive (we frequently ‘lose’ filtration time due to filters clotting/interventions etc.)

 

  1. Should I audit my current practice because of these results? Yes

 

Appraised by: Ewan JackDepartment of AnaestheticsWestern InfirmaryGlasgow; 24 February 2006

Email: ewanwendy@supanet.com

 

Kill or Update By: March 2010

 

Reviewed & edited by CC & SJM

 

Citation: EBM Critical Appraisals. Scottish Intensive Care Society EBM Group. 2006. Jack E. Ronco C, et al. Effects of different doses in continuous veno-venous haemofiltration on outcomes of acute renal failure: a prospective randomised trial. Lancet 2000 Vol 356 (9223) 26-30

 

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