Saturday, August 1, 2009

Prophylactic hemodialysis for iv contrast exposure?

The issue comes up all the time: you try and set up one of your ESRD patients for a procedure requiring iv contrast, such as a cardiac catheterization or a PE-protocol CT scan. You get a call from radiology saying that they won't do the test until you, as the representative for the nephrology team, can guarantee the patient will be promptly dialyzed so that the patient will not feel the ill effects of iv contrast exposure. Does this make sense? Is there any data to guide us here? Perhaps more importantly, would it be possible to prevent contrast nephropathy from occurring at all in patients with advanced CKD but not on dialysis?

On the one hand, one might expect dialyzing away contrast to be a beneficial thing. There has been increasing data suggesting that residual renal function--even in patients on dialysis--can be a good thing. iv contrast is definitely of low enough molecular weight to allow it to be efficiently dialyzed.

HOWEVER--most of the actual data runs counter to this position. One particular study by Vogt et al performed a randomized controlled trial in which patients with a baseline Cr greater than 2.3 md/dL were randomized to receive either prophylactic hemodialysis or not immediately after iv contrast exposure. The creatinine was initially lower in the treatment group (as would be anticipated given the effect of dialysis on reducing creatinine levels) but by Day 6 there was no signficant difference between treatment and control groups--and there was even a suggestion that dialysis could be harmful. You can find studies reporting the opposite finding--that is, a potential beneficial effect of prophylactic dialysis on contrast nephropathy, such as this recent study by Lee et al--but in my opinion the suspected mechanism by which iv contrast causes renal injury would cast doubt on such a strategy. iv contrast's toxicity is thought largely due to its high osmolar content, as evidenced by the appearance of intracellular vesicles in the renal tubular epithelium exposed to iv contrast. I would imagine that this tubular damage occurs rapidly after iv contrast exposure, and removal of contrast by dialysis would likely occur after the fact.

My own approach to the dilemma above: agree to dialyze the patient in order to get the test performed promptly. Evaluate the patient after the exam and see whether or not there is any objective reason to dialyze them earlier than their usual schedule would warrant. In rare instances, large amounts of iv contrast can cause volume overload/pulmonary edema. But in the majority of these instances, my suspicion is that prophylactic dialysis either to prevent contrast nephropathy in a patient with CKD or to preserve residual renal function in a patient with ESRD is not useful.

4 comments:

Warren said...

Totally agree.

PatelUTMEM said...

FDA recommends to dialyze ESRD patients after MRI scan/gadolinium. How is this approached at other institutions like yours?

Peter Laird, MD said...

Having spent many years working side by side cardiologists and surgeons, the issue of trust and respect is predicated on speaking ones mind and keeping promises. I believe telling a colleague you will dialyze a patient but don't really mean it will break that line of trust.

In the community hospital setting, that sort of transaction will lead to your colleagues finding another nephrologist who they will be able to trust to keep their word about providing care to their patients, no matter what the data shows about dialysis after contrast studies.

For a patient already on dialysis, providing early dialysis will not harm this patient and perhaps there is a margin of benefit not teased out in studies that are not that large. Keeping the good name of good promises is an imporant part of practice. Agreeing to do something that you likely will not do will not sell well in the real world of medicine.

nathanhellman said...

Thanks to all for the comments.

Regarding the gadolinium issue: the current policy at our hospital is to (1) avoid giving gadolinium to ESRD patients unless it is a study which needs to be done and there is no alternative, and (2) in the instance where gadolinium is given, dialysis is performed soon after exposure. There is not much data to guide us here but dialysis is effective at lowering serum gadolinium concentrations.

Regarding the important comments by Dr. Laird: I do not mean to suggest being intentionally duplicitous in dealing with one's colleagues. I am suggesting instead that as nephrologists we should really think about the indications of the dialysis procedure and what it aims to accomplish rather than blindly following the recommendations of another department (in this example, radiology) whose guidelines may be more based on protecting themselves from any threat of medicolegal liability than what is supported in the medical literature. Obviously, good communication and trust between nephrologist/cardiologist/radiologist is essential, and I did not adequately point this out in my post as clearly as Dr. Laird did.