Friday, April 09, 2010

Hospital Medicine 2010 April 9 sessions---selected nephrology pearls

Derek Fine, MD gave a talk on renal problems in hospitalized patients and noted---

It’s the CYP 34A interactions that often get us into trouble with statin myopathy leading to renal failure. Simvastatin has the worst reputation for this but lovastatin does it too and, to a lesser extent, atorvastatin. Read the labeling!

Don’t forget acute interstitial nephritis. Non-classic presentations are increasingly recognized. (Although not on the list of usual suspects a quick PubMed search revealed PPIs, vancomycin and Cox 2’s as recently recognized causes [1] [2] [3] [4] [5] [6]). Rx: stop the drug, and sometimes steroids.

Renal failure after cardiac cath? Consider atheroembolic etiology rather than contrast induced if onset over 48hrs post or no evidence of recovery in 5 days, particularly if systemic signs/sx.

Iodinated contrast nephropathy? Nothing new there, really, but here’s a Dr. RW bias: If you need to rule out PE why not V/Q instead of CT? It’s just as good in many cases.

Don’t forget phosphate nephropathy (can cause AKI sometimes followed by CKD).

Normal saline as a cause of resistant HT in hospitalized patients? We’re not used to thinking that way. It takes a boat load of saline to resuscitate. Traditionally we have under-resuscitated patients. Why be concerned about hypertension? Because some hypertensive patients are salt sensitive. Even “keep open” normal saline provides a significant sodium load. Look at the periodic table and do the math: 23mg/meq. This is not to advocate for hypotonic fluids in hospitalized patients, because such fluids fairly predictably lead to hyponatremia. The point is to keep in mind that in salt sensitive patients what may seem to be nominal amounts of saline may contribute to resistant hypertension.

Nephrogenic systemic fibrosis, the latest scleroderma mimic, is on the radar screen. I mentioned contraindications to contrast MRI and the relative safety of Gadolinium preparations the other day. In exceptional cases a patient with contraindications absolutely, positively has to have a contrast MRI. Then what? Use the lowest risk agent at the lowest dose possible followed by intensive hemodialysis using special methods.

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