ACE inhibitors reduce symptoms of CHF in patients with myocardial dysfunction, and provide long-term morbditiy and mortality benefits. They are good for hypertensive patients who have proteinuria and/or diabetes. This is like CHF Meds 101. ACE inhibitors are also good for the kidneys. But there are some important caveats that you should be aware of.
ACE inhibitors can cause a slight creatinine bump.
ACE inhibitors dilate efferent arterioles more than afferent arterioles. This increases renal blood flow and glomerular capillary hydrostatic pressure, while keeping the GFR the same or slightly less. Therefore, a slight rise in creatinine (usually 10-20%) can occur after an ACE inhibitor is given for the first time, and this could be a good thing! It means the ACE inhibitor is doing its job.
ACE inhibitors can cause acute renal failure.
There are several ways this can happen:
- Remember that ACE inhibitors are a major antihypertensive agent. If an ACE inhibitor decreases the MAP, it can lead to hypoperfusion, leading to pre-renal AKI.
- ACE inhibitors can “push people over the edge” towards hypovolemia if they are already on a diuretic regimen.
- ACE inhibitors are not good for patients who rely on a dominant kidney (transplant recipients) or have stenosis in their arterioles (renal artery stenosis, severe atherosclerotic disease) because of their vasoconstrictive effects.
- They are also not good in combination with other vasoconstrictive agents, like NSAIDs, or less commonly, cyclosporine.
ACE inhibitors make patients more sensitive to possible renal insults than they might otherwise be.
Plenty of things precipitate acute kidney injury: infection, hypovolemia secondary to severe diarrhea, CHF exacerbation, shock, contrast-induced nephropathy, etc. The kidney’s way of protecting itself is to activate angiotensin II to increase glomerular capillary pressure. This is exactly what ACE inhibitors prevent.
So when can they be restarted on their home ACE inhibitor?
Just because you withhold an ACE inhibitor while a patient is hospitalized doesn’t mean they can’t take if afterward. As long as a patient is hemodynamically stable and renal function appears to be returning, they can be restarted on the ACE inhibitor, but will likely need follow up labs in the outpatient setting.
For more information, see this awesome American Heart Association statement on ACE inhibitors and acute renal failure.