Daily hemodialysis and the outcome of acute renal failure.
This review may be edited
Posted By: Gordon S. Doig
Posted Date: 26/02/2002
Title: Daily hemodialysis and the outcome of acute renal failure.
Authors: Schiffl H, Land SM and Fischer R.
Reference: N Engl J Med 2002;346:305-10
Link: Click here for a direct link to the paper. A password may be required for access to fulltext.
Abstract: BACKGROUND: Intermittent hemodialysis is widely used as renal-replacement therapy in patients with acute renal failure, but an adequate dose has not been defined. We performed a prospective study to determine the effect of daily intermittent hemodialysis, as compared with conventional (alternate-day) intermittent hemodialysis, on survival among patients with acute renal failure.
METHODS: A total of 160 patients with acute renal failure were assigned to receive daily or conventional intermittent hemodialysis. Survival was the primary end point of the study. The duration of acute renal failure and the frequency of therapy-related complications were secondary end points.
RESULTS: The two study groups were similar with respect to age, sex, cause and severity of acute renal failure, medical or surgical intensive care setting, and the score on the Acute Physiology, Age, and Chronic Health Evaluation. Daily hemodialysis resulted in better control of uremia, fewer hypotensive episodes during hemodialysis, and more rapid resolution of acute renal failure (mean [+/-SD], 9+/-2 vs. 16+/-6 days; P=0.001) than did conventional hemodialysis. The mortality rate, according to the intention-to-treat analysis, was 28 percent for daily dialysis and 46 percent for alternate-day dialysis (P=0.01). In a multiple regression analysis, less frequent hemodialysis (on alternate days, as opposed to daily) was an independent risk factor for death.
CONCLUSIONS: The high mortality rate among critically ill patients with acute renal failure who require renal-replacement therapy is related to both coexisting conditions and uremic damage to other organ systems. Intensive hemodialysis reduces mortality without increasing hemodynamically induced morbidity.
Are the Results Valid?
1. Was the assignment of patients to treatments randomized? ( Was allocation concealment maintained?)
No. At the bottom of page 306 the authors report that 'Consecutively enrolled patients were assigned in alternating order to receive daily or conventional hemodialysis'.
Alternating allocation is often referred to as pseudo or quasi-randomization. When a clinical trial allocates patients to treatments using an alternating fashion, it becomes extremely difficult to maintain 'concealment'. Concealment occurs when the person who is recruiting patients to the trial does not know which treatment the potential participant will receive before they are recruited. If the person doing the recruiting can determine the allocation pattern, it is possible that recruitment bias can occur, which could result in the person subconsciously pre-selecting patients for each treatment arm.
2. Were all patients who entered the trial properly accounted for and attributed at its conclusion?
2a. Was followup complete?
Follow-up was complete. Figure 1 on page 308 presents the loss to follow-up on each and every patient by arm.
2b. Were patients analyzed in the groups to which they were randomized?
Yes. An intention to treat analysis was performed.
3. Were patients, health workers, and study personnel blind to treatment?
No. Although it is reported that 'To minimize bias in the selection of patients, a number of precautions were taken', non of the procedures that were described appear adequate to support concealment. Due to the alternaing allocation schedule, anyone who could 'remember' which treatment the last patient received could easily determine which treatment any subsequent patients would receive. For an interesting paper on the importance of concealment, please see Kenneth F Schulz, David A Grimes. Allocation concealment in randomised trials: defending against deciphering. Lancet 2002; 359: 614-18
There was no mention of any other level of blinding, which could have included outcome adjudication, analysis etc.
4. Were the groups similar at the start of the trial?
It would appear that the factors presented in Table 1 are in balance.
5. Aside from the experimental intervention, were the groups treated equally?
A table of concommittent interventions was not presented.
What are the Results?
1. How large was the treatment effect?
The investigators report a significant decrease in mortality at 14 days from 46% in the every other day dialysis group to 28% in the daily dialysis group (p=0.01).
2. How precise was the estimate of the treatment effect?
The 95% confidence interval for the mortality estimate extends from 4% to 33%.
Will the Results Help Me In Caring For My Patients?
1. Can the results be applied to my patient care?
First it should be understood that due to the potential for bias in alternating allocation studies, this paper should probably best be viewed as Level III evidence.
As such, if your ICU sees patients similar to the ones entered into this study, it is reasonable to assume that the benefits may be similar.
2. Were all clinically important outcomes considered?
Length of ICU and hospital stay was not reported. Quality of life could have been important to consider.
3. Are the likely treatment benefits worth the potential harms and costs?
Since this is not a true RCT and costing for the extra work of daily dialysis was not included, it is difficult to answer this question.

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Daily hemodialysis and the outcome of acute renal failure.

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