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Correspondence |
University of Alberta, Edmonton, Canada, E-mail: mjacka{at}ualberta.ca
We thank Tonelli et al. for their interest in our study showing improved renal recovery among patients treated with continuous renal replacement therapy (CRRT).1
As we described, ours was a non-randomized observational study. The ‘issue of crossover’ should not affect interpretation, even adopting a ‘worst case scenario’. Crossovers were very few and occurred only among patients who had stabilized on CRRT from the indications precluding intermittent hemodialysis (IHD). Crossovers would be a concern in a randomized trial, among patients assigned to IHD but who required CRRT due to hemodynamic instability, and who would probably die without renal replacement.
Second, the risks of dialysis-dependence and death might be an appropriate composite outcome measure in a prospective randomized analysis. In our study, as we pointed out in the methods and discussion, CRRT was applied to patients who had sufficient hemodynamic instability, intracranial hypertension, or liver failure that made use of IHD impossible. The finding of any survivors among these CRRT patients supports the use of CRRT, making randomized evaluation unethical.
Third, most studies comparing CRRT and IHD have used mortality and renal recovery as separate outcome measures, rather than composites. Tonelli et al. have suggested that studies comparing modes of RRT should concentrate on renal recovery.2 No study has found hospital mortality ‘due’ to CRRT as implied by Tonelli.
Fourth, although serum creatinine was higher at intensive care unit admission among IHD patients, careful examination of our tables shows that at the time of institution of RRT, and as we pointed out in our discussion, serum creatinine was similar between groups.
Fifth, we agree that meta-analysis has limitations. Although Tonelli failed to find a benefit from CRRT, Kellum showed lower mortality with CRRT when patients were stratified according to severity of illness.2,3
Sixth, CRRT has been shown to have specific advantages over IHD. CRRT minimizes hemodynamic fluctuation in unstable patients and prevents further elevation of intracranial pressure in patients with fulminant liver failure.4 CRRT is superior in correcting azotemia and acidosis and is recommended for patients with severe sepsis.5,6
While we support Tonelli et al. in their advocacy of the least costly alternative, insistence on minimizing cost in the face of evidence of benefit represents an inappropriately regimented approach. Finally, we thank Tonelli et al. for helping us to stimulate and inform debate on the issue of renal replacement among the critically ill, along with our descriptive study.
References
1 Jacka MJ, Ivancinova X, Gibney RT. Continuous renal replacement therapy improves renal recovery from acute renal failure. Can J Anesth 2005; 52: 327–32.
2 Tonelli M, Manns B, Feller-Kopman D. Acute renal failure in the intensive care unit: a systematic review of the impact of dialytic modality on mortality and renal recovery. Am J Kidney Dis 2002; 40: 875–85.[Medline]
3 Kellum JA, Angus DC, Johnson JP, et al. Continuous versus intermittent renal replacement therapy: a meta-analysis. Intensive Care Med 2002; 28: 29–37.[Medline]
4 Davenport A, Will EJ, Davison AM. Early changes in intracranial pressure during haemofiltration treatment in patients with grade 4 hepatic encephalopathy and acute oliguric renal failure. Nephrol Dial Transplant 1990; 5: 192–8.
5 Uchino S, Bellomo R, Ronco C. Intermittent versus continuous renal replacement therapy in the ICU: impact on electrolyte and acid-base balance. Intensive Care Med 2001; 27: 1037–43.[Medline]
6 Dellinger RP, Carlet JM, Masur H, et al.; Surviving Sepsis Campaign Management Guidelines Committee. Surviving Sepsis Campaign guidelines for management of severe sepsis and septic shock. Crit Care Med 2004; 32: 858–73.[Medline]
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