Contrast Nephropathy: The Biggest Cause of Acute Kidney Injury that Might Not Exist

Contrast Nephropathy: The Biggest Cause of Acute Kidney Injury that Might Not Exist

A study appearing in Annals of Emergency Medicine suggests that iodinated contrast material, long-implicated in the pathogenesis of acute kidney injury, may have no role to play at all. For the video version, click here.

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Two Pressors, both Alike in Dignity? Vasopressin versus Norepinephrine and Renal Failure in Sepsis

Two Pressors, both Alike in Dignity? Vasopressin versus Norepinephrine and Renal Failure in Sepsis

A randomized trial appearing in JAMA found no difference in the rates of renal failure when patients with sepsis were given norepinephrine versus vasopressin. But some signal of a vasopressin benefit emerged.  For the video version of this post, click here.

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Now or Never? When to Start Dialysis for Acute Kidney Injury


An embarrassment of riches this week as we got not one, but two randomized clinical trials evaluating the timing of dialysis initiation in acute kidney injury.  Of course, the results don’t agree at all. Back to the drawing board folks. For the video version of this post, click here.

OK here’s the issue – we nephrologists see hospitalized people with severe acute kidney injury – the abrupt loss of kidney function – all the time.  There is always this question – should we start dialysis before things get too bad, in order to get ahead of the metabolic disturbances, or should we hold off, watch carefully, and jump when the time is right? Several people – and, full disclosure, I’m one of them – have examined this question and the answers have been confusing.  The question begs for a randomized trial.

And, as I mentioned, we have two.  One, appearing in the Journal of the American Medical Association, says yes, earlier dialysis is better with mortality rates of 40% in the early arm versus 55% in the late arm. The other, appearing in the New England Journal of Medicine says there is no difference – mortality rates were 50% no matter what you did.


Figure 1: JAMA Trial - GO TEAM EARLY!


Figure 2: NEJM Trial - D'Oh!

Sometimes, rival movie studies put out very similar movies at the same time to undercut each other’s bottom line. So which of these trials is Deep Impact, and which is Armageddon? Which is Ed TV and which is the Truman show? Which is Jobs and which is Steve Jobs?


Figure 3: It's like looking in a mirror...


In this table I highlight some of the main differences:


The NEJM trial was bigger, and multi-center, so that certainly gives it an edge, but what draws my eye is the difference in definitions of early and late.

The NEJM study only enrolled people with stage 3 AKI – the most severe form of kidney injury. People in the early group got dialysis right away, and the late group got dialysis only if their laboratory parameters crossed certain critical thresholds.  The JAMA paper enrolled people with Stage 2 AKI. In that study, early meant dialysis right after enrollment, and late meant dialysis started when you hit stage 3.

OK so definitions matter. The NEJM trial defined early the way the JAMA trial defined late. So putting this together, we might be tempted to say that dialysis at stage 2 AKI is good, but once you get to stage 3, the horse is out of the barn – doesn’t matter when you start at that point.

That facile interpretation is undercut by one main issue: the rate of dialysis in the late group.


See, one of the major reasons you want to hold off on dialysis is to see if people will recover on their own. In the JAMA study, enrolling people at stage 2 AKI, only 10% in the late group made it out without dialysis – and those people were dialyzed, on average, only 20 hours after randomization. In the NEJM study, using the more severe inclusion criterion, roughy 50% of the late group required no dialysis. To my mind, if 91% of the late group got dialysis, you’re not helping anybody – the whole point of not starting is so that you never have to start, not that you can delay the inevitable.

Regardless of your interpretation, these studies remind us not to put too much stock in any one study. They should also remind us that replication – honest to goodness, same protocol replication – is an incredibly valuable thing that should be celebrated and, dare I say, funded.

For now, should you dialyze that person with AKI? Take heart – there’s good evidence to support that you should keep doing whatever you’ve been doing.

Statins to prevent acute kidney injury after cardiac surgery


Statins, is there anything they can’t do? These agents, granted blockbuster status more than 20 years ago, are potent weapons in our fight against cardiovascular disease. But beyond their cholesterol-lowering effects, we’ve seen studies where statins act as anti-inflammatories, improve immune function and even stave off dementia.  Could the wonder-drugs prevent acute kidney injury, a dreaded complication after cardiac surgery, associated with more than a three-fold increase in mortality?

For the video version of this post, click here.

Full disclosure: I research acute kidney injury, or AKI. So welcome to my world, statins – a world where positive clinical trials are as rare as an epidemiologist at a Mr. Personality contest.

The trial, out of Vanderbilt university hospital appeared in JAMA and enrolled 617 individuals undergoing cardiac surgery. The treatment group got 80mg of atorvastatin prior to surgery, and 40mgs a day after that. The placebo group got, well, placebo. As you might imagine, the majority of patients (400) were already taking a statin.  In that case, if you were randomized to placebo, you only got placebo for the day of surgery and the day after. After that, you were back on your home statin dose.

And to boil the results down to a word: nothing. The rate of AKI was 21% in the statin arm and 20% in the placebo arm. Looking at secondary outcomes, there were no differences in rates of death, dialysis, delirium, stroke, or stay in the ICU.

This might be expected in the group that was already on statins – after all, skipping two days of the drug might not be enough to make a real difference. But if we look at the statin-naïve group, the rate of AKI was 22% in the statin group and 13% in the placebo group. This was not statistically significant but the trend here is clearly in the wrong direction. In fact, if we look at absolute creatinine change –where higher levels are worse- those on the statin had a small, but statistically significant increase in creatinine compared to those on placebo.

But take these numbers with a grain of salt. The data safety and monitoring board forced the study authors to stop recruitment of statin-naïve patients about 2/3rds of the way through the study. They did this because they saw a signal of harm from statins in that group. So the fact that we see harm may be biased by the DSMBs choice to stop that part of the study early.

Now, would I have stopped the study if I were on the DSMB?  Probably. The odds that continuing to recruit would show a benefit of statin were really low, and you don’t want to expose patients to potential harm. But despite that, we can’t accept the results of an early-termination arm of a trial with the same gusto that we would had the trial continued to completion.  In short, the jury is still out as to whether statin use is actually harmful in terms of AKI. But I can say for now I’m pretty convinced it ain’t helping anybody.


Our latest study suggests that we may be diagnosing a LOT of people with acute kidney injury who don't actually have it.


Acute kidney injury (AKI) is a major killer in the US. At least, that's what the data shows. But a lot depends onhow you diagnose AKI. Our latest study suggests that natural variation in lab measurement of creatinine is leading to strikingly high false-diagnosis rates, and that the association we see between AKI and bad outcomes like mortality may be an artifact of the fact that sicker people get more blood draws. Take a look at our full paper here.

And if you want to run the simulation for yourself (and you have stata), you can get our code and relevant files here.