Wednesday, October 12, 2011

Renal-dose dopamine... still a myth (Part 1)

A colleague asked me to re-post an old entry I wrote about renal-dose dopamine:

Every once in a while, I hear about instances where low-dose (i.e., "renal dose") dopamine is attempted as a strategy for improving outcomes in critically ill patients with renal failure. The practice was first studied in the early 1960s and has been the subject of controversy ever since. After publication of the ANZICS trial and the large meta-analysis to follow, I thought the practice would have disappeared altogether, but the debate still seems to come up from time to time.

Using low-dose dopamine to correct renal dysfunction seems intuitive from a physiologic standpoint, given that at low doses (1-3 mcg/kg/minute), the agent increases renal blood flow and improves urine output -- in healthy volunteers. However, these effects have yet to confer any clinically substantial benefits in patients with renal failure.

In ANZICS, the largest randomized placebo-controlled trial to date, low-dose dopamine did not improve serum creatinine elevations, urine output, need for renal replacement therapy, intensive care unit stay, total in-hospital stay, or mortality compared to placebo. A large meta-analysis by Friedrich et al, which included results from ANZICS, found similar results -- low-dose dopamine only provides a mild and transient benefit in urine output but no improvement in renal function or mortality. The authors attribute the continued popularity of low-dose dopamine to the limited improvement in urine output seen in the first 24 hours, an effect that was not significant versus placebo at any other point in time. This may also help explain some of the anecdotal cases observed in clinical practice. The authors contend that an extremely large trial would probably be necessary to observe a clinically meaningful benefit from low-dose dopamine -- a trial that would probably be of sufficient size to also reveal its adverse effects.

When used in hemodynamically stable patients outside the intensive care unit, low-dose dopamine is probably ineffective at best and benign at worst. While its adverse effect profile is probably minimal at 1-3 mcg/kg/min, low-dose dopamine does still carry an increased risk of myocardial ischemia and tachyarrhythmia in patients with unstable hemodynamics at baseline.

What may renew the debate in some patient populations is the recently published DAD-HF trial, where low-dose dopamine added to diuretics was compared to diuretics alone in patients with acute decompensated heart failure. More on that -- and more importantly, the specific patient population studied -- in a future entry.

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