Henry R. Black, MD; Domenic A. Sica, MD


June 06, 2012

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Henry R. Black, MD: Hi. I'm Dr. Henry Black.I'm Clinical Professor of Internal Medicine at the New York University School of Medicine and a member of the Center for the Prevention of Cardiovascular Disease at that institution. I am here today with Dr. Domenic Sica. Dom?

Domenic A. Sica, MD: Thank you. I'm Dr. Domenic Sica, Professor of Medicine and Eminent Scholar at Virginia Commonwealth University Health System in Richmond, Virginia. I am also President-Elect of the American Society of Hypertension.

Dr. Black: One thing I would look to you for advice about is what to do with a patient who has hypotension. I am very concerned when a patient is referred to me with postural hypotension. What is your approach to that?

Dr. Sica: To be careful. I think a lot of what we do is recognition. By the time you get a referral from someone, it has probably been present for much longer but just hasn't been picked up. The weakness and dizziness when sitting or standing in the upright position, which goes unrecognized as a blood pressure reduction symptom, is key. About 10%-20% of individuals with type 2 diabetes will have some element of postural change in blood pressure in the upright position. The basis for this is typically a blunted heart rate response to a postural challenge. When you stand, you pool the lower extremities, which can be 500 cc to 1 L of pooling. We have a blood volume of 6-7 L, so you are redeploying about one sixth of your blood volume. A heart rate response would compensate for that, but when you don't, blood pressure drops.

Dr. Black: Would that happen to people on beta-blockers?

Dr. Sica: If you have a little bit of a heart rate response and you are blunted, then that is a problem. If you have a flat heart rate response of 60 beats/min and you are at 60 beats/min when you stand up, the beta-blocker probably won't do much harm unless it systematically lowers the basal heart rate, of which there is no guarantee of happening. If a patient with coronary artery disease needed beta blockade for something other than heart rate control, it may be tried at a low dose.

Dr. Black: Could you do the same thing with verapamil or diltiazem?

Dr. Sica: Verapamil has a little bit too much of a vasodilating effect, so the pressure will drop more. Beta blockade will drop blood pressure for reasons that are independent of changing peripheral resistance, so identifying hypotension becomes key. Once you identify it, you have 3 systematic approaches. First, separate it into upright position, orthostatic hypotension, and supine hypertension (assuming the supine position automatically allows for a shift of pooled blood). You have to deal with each one by implementing different measures to control the pressure. If blood pressure goes down when your patient stands up, then you need to use compression stockings (30-40 mm Hg gradient, waist high, pantyhose style), which are, unfortunately, difficult to put on, but they are often very useful in limiting the pooling in the lower extremities. Next, try to expand the blood volume. This is generally done with a high salt intake with or without fludrocortisone, which is a sodium-retaining hormone, and some potassium supplementation.

Dr. Black: But isn't the patient at risk for supine hypertension?

Dr. Sica: Yes, but you are trying to keep the pressure from going down when the patient stands up. When you are treating the upright hypotension, your goals are volume expansion and vasoconstriction. The vasoconstriction can be a function of something like midodrine, which is a pure alpha agonist. You are trying to come up with something that allows some semblance of sanity for your patients when they walk around. We use stockings, salts, fludrocortisone, and midodrine. If these patients sit or lie down very quickly, they will get hypertensive, so you have to teach them the tricks for mitigating those circumstances.

Dr. Black: What tricks?

Dr. Sica: Semi-recumbent sitting. The patient does not lie flat. He may lie at 30º. At night, the bed should be propped up on blocks, or if a hospital bed is available, it can be adjusted. The patient can eat something that is carbohydrate-laden prior to a meal, which will allow for redistribution of blood flow into the splanchnic bed and decrease the overall blood pressure. Short-acting substances such as nitropaste or the nitroglycerin patch, a little clonidine, or even a little amlodipine at a low dose can be used.

Dr. Black: But amlodipine is a long-acting drug. What about using captopril at night?

Dr. Sica: You can use captopril to a degree. It is unclear what the responses to the drugs are. Supine hypertension is a volume overload form of hypertension, and captopril tends to not work as well when you are volume overloaded. The calcium channel blocker works a little better in the volume-overloaded state.

For amlodipine, a traditional dose might be 2.5 mg. I get around the long-acting half-life by administering such a low dose that its effect would have dissipated soon after the patient gets up. If you put the nitropaste or the nitroglycerin patch on 20 minutes before you get out of the bed, you are actually pulling that off.

Dr. Black: What happens in the middle of the night when somebody gets up to go to the bathroom?

Dr. Sica: It is interesting that you would say that, because they do. Fluid retention occurs during the daytime, so a very useful survey question to ask your patients is how much weight they gain from morning until night and how much weight do they lose overnight. Then you take the amount of weight loss, divide it up, and determine what their urine output is. Most people with orthostatic hypotension, based on the amount of fluid and salt they take in, gain 2-6 lb during the day. At night, they will get rid of close to 2-6 lb. Based on bladder capacity being smaller in women and men having prostate disease, that is probably 3-4 voids at night. Even when you look at nighttime blood pressures, it is an interesting phenomenon. People begin to diurese overnight, and based on the pressure natriuresis, they become less hypertensive because they are eliminating some of what they retained the day before. You have to take precautions. They can't just get up on their own, because they will fall down on you very easily. You have to teach the patient about the disease.

Dr. Black: Do you do ambulatory blood pressure monitoring on a patient with that problem?

Dr. Sica: Not often, but it certainly is a tool that can be used. I say that because a not inconsequential portion of people with orthostatic hypotension have sympathetic dysregulation sufficient to make their pressures go up randomly during the day in a very unpredictable way, even when their pressures are otherwise low. Sometimes you are trying to figure out what stressors are triggering catecholamine release during the day that then creates an abundance of hypertension even when the patient is in the upright position. These are very complex patients and some of the most difficult ones I have to manage.

Dr. Black: Besides diabetes and Parkinson's, which are the 2 things I most expect to see in somebody with this problem, are there other conditions that this is commonly associated with?

Dr. Sica: Yes. We all have latent tendencies towards astasis, but some people decondition rapidly. For example, let's say you get sick and you are in bed for 7-10 days, and you decondition similarly to astronauts when they are exposed to zero gravity. When you try to get up, you unmask that latent tendency immediately. Deconditioning is a key issue. Subtle volume changes bring out latent tendencies, as do seasons of the year. In the summer, you can expect to vasodilate. You will see more issues with this in the summer vs the winter. It's seasonal issues, it's deconditioning, it's heat exposure. If you take a good history from your patients, you can ask them how they bathe -- whether they bathe or shower. If they take a long, warm shower in the upright position and they tell you that they are dizzy when they get out of the shower, that is another subtle clue that we use to recognize postural-related blood pressure changes. I think there are other issues that make latent tendencies manifest.

Dr. Black: Thank you very much. This is a complicated problem that I think we are going to see more of as we get older and have more diabetes to contend with.