Increasing the intensity of continuous renal-replacement therapy (CRRT) does not reduce mortality among critically ill patients with acute kidney injury (AKI), new findings suggest.

AKI severe enough to require CRRT affects approximately 5% of patients admitted to an intensive care unit (ICU) and is associated with a mortality rate of 60%. Although previous studies have attempted to determine the optimal approach, intensity, and timing of CRRT, it remains unclear as to which method is best.

In a multicenter, randomized trial of 1,508 critically ill adults with AKI, investigators from the Australian and New Zealand Intensive Care Society Clinical Trials Group and the George Institute for International Health randomly assigned 747 patients to receive a higher-intensity dose (40 mL/kg/hour) of continuous venovenous hemodiafiltration and 761 to receive a lower-intensity dose (25 mL/kg/hour). The participants received the study treatment for an average of 6.3 and 5.9 days, respectively.

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At 90 days after randomization, death occurred in 322 (44.7%) of 721 patients in the higher-intensity group and in 332 (44.7%) of 743 patients in the lower-intensity group, the researchers reported in The New England Journal of Medicine (2009;361:1627-1638). In addition, 6.8% of survivors in the higher-intensity group were still receiving CRRT compared with 4.4% of those in the lower-intensity group, a difference that was not statistically significant.

The two groups did not differ significantly in the proportion of patients who underwent intermittent hemodialysis at any time during their ICU stay (7.6% in the high-intensity group vs. 7.0% in the lower-intensity group).

Hyperphosphatemia was significantly more common in the higher-intensity than the lower-intensity group (65% vs. 54%). In addition, patients receiving higher-intensity therapy were more likely to receive regional extracorporeal-circuit anticoagulation with heparin and protamine and required more filters per day.

The authors concluded that their findings “suggest not that the intensity of renal-replacement therapy is unimportant but rather that increases beyond an adequate level of intensity provide no additional benefit in critically ill patients.

The results also suggest that some specific aspects of renal-replacement therapy in critically ill patients – that is, the effect of the timing of treatment initiation on mortality and the effect of continuous as compared with intermittent treatment on renal recovery – should be prioritized for investigation in future trials.”