Kidney injury and ACE inhibitors

Today in morning report we touched on the perils of volume depletion in patients who are taking ACE inhibitors. Have you ever wondered why this situation would precipitate acute kidney injury?



The issue is this: ACE inhibitors offload the glomerulus (and thus protect it from wear-and-tear) by causing efferent arteriolar dilatation. Normally in situations of volume depletion, the Renin-Angiotensin system is activated, and angiotensin II causes efferent arteriolar constriction, thus increasing the pressure in the glomerulus (think of it as a "squeeze") and thus preserving GFR. If you have a ACE inhibitor (or ARB) on board then you don't get the efferent constriction, thus no squeeze, thus drop in GFR. This causes AKI.

Patients on ACE inhibitors should be warned about this complex issue. While the ACE inhibitor protects their kidneys in the longterm, it can hurt them in the short term if your patients takes his ramipril while volume depleted. So please hold it if there is diarrhea, vomitting, decreased PO intake, bleeding etc.

Cheers! Have a great long weekend!