Robert W. Morrow, MD: Hi. This is Dr. Bob Morrow, a family physician in the Bronx. Welcome to our new series, "Primary Care in Urinetown." We are talking about some difficult or interesting issues in nephrology and primary care. I am a family physician and Clinical Associate Professor in the Department of Family and Social Medicine at the Albert Einstein College of Medicine. We have Dr. Lynda Szczech here, who is going to introduce herself. Then we will talk about our topic for today.
Lynda A. Szczech, MD: My name is Lynda Szczech. I am a nephrologist, and I practice in Durham, North Carolina. I would like to give a plug for our last chat, Worsening Kidney Function -- What to Do With ACEIs and ARBs?.
Dr. Morrow: We are going to talk about blood pressure. The question is how aggressive to be in lowering blood pressure. When do we lower it too little, and when do we lower it too much? Which guidelines should we be following? Around the world there are several major differences in guidelines, particularly in the prevention of chronic kidney disease and kidney failure. What do you think?
Dr. Szczech: We could recite all of the various guidelines and talk about the trials that support those guidelines, and it would probably be very dry and not very helpful. So, I would like to approach it from a very practical perspective. Let's put the focus on proteinuria first. If you have a patient with substantial proteinuria with a glomerular disease, the amount of protein in the urine is probably more important than the blood pressure. Let me tell you what I mean by that. When it comes to titrating blood pressure medicine in someone with hypertension, you would titrate using the blood pressure as your intermediate outcome. Without proteinuria, you want that number to be low. We will put those people aside for the moment, but in someone with glomerular disease, the proteinuria is really the number that is most important, because if you get them under somewhat good blood pressure control using an alpha-blocker or a calcium channel blocker and you haven't affected their proteinuria, you are not going to change the outcome in terms of kidney disease.
In someone with proteinuria, there is another trick. Verapamil and diltiazem act like an angiotensin-converting enzyme (ACE) inhibitor at the level of the glomerulus. Keep an eye on the proteinuria and reduce it as much as you can, to approximately 1 g/day if possible. I always get greedy and want it below 1 g/day, but if you can get proteinuria down to a 1 g/day, that person is going to be a happy camper because of all those things that result from lower proteinuria, such as lower blood pressure.
For people who don't have proteinuria, what are the numbers? I am not aware of any data that support a J-shaped curve in people with kidney disease. We talk about it in theory with cardiovascular disease and cerebrovascular disease, but in terms of kidney disease, data don't support a link between low blood pressure and kidney outcomes.
So, what numbers do we shoot for? Joint National Committee-7 [Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7)] says 130/80. It makes plenty of sense to me, because although I said I wasn't going to get into the trial data, when you look at the African American Study of Kidney Disease and Hypertension, and a whole host of others, there didn't seem to be a whole lot of bang for your buck by lowering blood pressure below 130/80. It really is all about the agents. In terms of those agents, ACE inhibitors and angiotensin-receptor blockers (ARBs) are fabulous. The pearl that I want to add is that diltiazem and verapamil (not the other calcium channel blockers, nifedipine and amlodipine) both decrease the preglomerular arterial pressure and lower intraglomerular pressure, so these agents are ACE inhibitor and ARB equivalents.
Dr. Morrow: That is helpful. Are you measuring spot urine albumin, or are you measuring 24-hour urine albumin levels?
Dr. Szczech: I do spot urines. As you get toward greater amounts of proteinuria, you get more error. If you have a patient with 28 g/day of protein in their urine, the error for that is huge, but in spite of the error you can still see the trend over time. You should check it every 3 months when you are doing titration. The error takes care of itself as long as you have a trend in the right direction.
Medscape Family Medicine © 2012
Cite this: Robert W. Morrow, Lynda A. Szczech. Managing BP in the CKD Patient: Check Out Proteinuria - Medscape - Aug 16, 2012.