Dizziness usually occurs in PD because of orthostatic or postural hypotension (a drop in blood pressure on sitting or standing). To understand why your blood pressure drops, you must understand hypertension or high blood pressure.
Your brain and heart need a constant flow of blood, a constant cardiac output, under all conditions: lying down, sitting, and standing. Your brain demands 30% of your cardiac output, and your heart about 20%. If your brain does not get its 30%, it shuts down and you black out.
We cannot easily measure blood flow, but we can measure blood pressure. As you grow older, your arteries narrow and their resistance increases. To maintain 30% of blood flow to your brain, your blood pressure must increase to compensate for the increased arterial resistance. In PD, orthostatic hypotension results from an inability of a faulty autonomic nervous system (ANS) to constrict your arteries when you sit or stand. Ortho-static hypotension occurs in about 20% of PD patients, and almost all patients with MSA.
When you lie down, your head and your heart are at the same level, so your heart does not have to work hard to pump blood to your brain. When you sit, your head is above your heart, and your heart has to work harder. In part, your heart works harder by beating faster, and in part you constrict your blood vessels.
However, if you can’t constrict your blood vessels or your heart can’t beat faster—your brain will get less blood and you’ll feel dizzy or faint. Likewise, when you stand after sitting, fluid (the equivalent of two units of blood) is redistributed from your chest and abdomen to your legs. To accommodate the larger volume of distribution, your heart has to work harder to pump blood to your brain. Again, your heart works harder by beating faster and constricting your blood vessels.
The following letter from a woman whose husband has MSA illustrates what you can do to manage orthostatic hypotension. If she can do it—so can you.
My husband was diagnosed with MSA. The symptoms that are most difficult to deal with are his orthostatic and postprandial hypotension (decreased blood pressure after eating). His postprandial hypotension is more dramatic because it causes his blood pressure to crash after he eats, which often results in his passing out. His orthostatic hypotension results in balance problems and falling, as well as in his passing out.
Note that after you eat a standard sized meal, 30% of your blood supply goes to your stomach. This puts an even greater demand on your heart if you stand: 30% of your blood must go to your brain, but 30% is already going to your stomach. If you have orthostatic hypotension, lie down after you eat, especially after a large meal.
I take my husband ’s blood pressure several times a day. It was through my discovery of lying him down and taking his blood pressure that I noticed it was always high (supine hypertension). I then discovered that if he passed out and I called “911” the paramedics would put him on a stretcher, which caused his blood pressure to increase.
Thus by the time he arrived in the Emergency Room (ER) the doctor was treating his supine hypertension, and NOT his orthostatic hypotension. But when he returned home the orthostatic hypotension on sitting or standing became the problem—again. Through trial and error, I learned and convinced the doctors that, in addition to orthostatic hypotension, he also had supine hypertension.
We’re between a rock and a hard place and so we’ve taken the approach, rightly or wrongly, that we prefer the high blood pressure over the low. With high pressure, the risk is theoretical: it’s not immediate. With orthostatic hypotension the risk is real and immediate. We treat the low blood pressure with pressure stockings, adequate fluids and salt, fludrocortisones or Florinef (a volume expander), mido-drine or Proamatine (a drug that simulates the action of norepinephrine), and neostigmine (a drug used in myasthenia gravis, but one that can prevent the development of orthostatic hypotension without provoking supine hypertension).
In addition to having orthostatic hypotension and supine hypertension, people with MSA (and some people with PD) can have bradycardia, a slow heart rate (fewer than 50 beats/minute). If you stand up and your blood pressure drops, your heart rate usually increases to maintain the same flow of blood to your brain.
This is what prevents you from passing out. However, if, when your blood pressure drops, you can’t increase your heart rate (because of a prob-lem with your ANS), then you pass-out. The slow heart rate can be treated with a pacemaker. Although on occasion my husband ’s heart rate has slowed below 50 beats/minute, at this time we have decided NOT to have a pacemaker.
MSA has made me learn things I never wanted to know, but it has made me my husband ’s advocate. I check his blood pressure every morning when he gets out of bed; this is usually the time of his lowest pressure. He has learned NOT to jump out of bed, because his pressure drops dramatically.
He first sits at the edge of his bed and dangles his legs. Then, with help, he slowly gets out of bed. If he’s dizzy, and his pressure is too low, we put him back in bed, wait a few minutes and try again. Some days it takes several attempts before he’s ready to stand and his blood pressure has adjusted to his standing position. The bathroom is a problem. When a man stands and urinates, his blood pressure may drop as he empties his bladder. The faster he empties his bladder, the more his pressure drops.
If it drops too much, he can black out. This is called micturition syncope. My husband has learned never to stand when he urinates and he has learned to urinate slowly.
My husband spends 30 minutes a day on a recumbent bicycle. On the bicycle, his head and heart are almost at the same level, so it’s easier for his heart to pump blood to his head and he’s less likely to black out while exercising. I give him midodrine, a drug that raises his pressure, an hour before he gets on the bicycle.
The midodrine can minimize the drop in blood pressure that some MSA and PD patients experience when they exercise. He pedals slowly; this improves the tone of his muscles, important because it’s the muscles that send blood from his veins to his heart. After he finishes with the bicycle, I massage his legs; I always start at his feet and massage upward, moving the fluid that has been trapped in his feet upward. The less fluid trapped in his legs, the more that is available to be pumped to his head.
A friend has a swimming pool and we use it three times a week. If the water is too warm, the blood vessels in his arms and legs dilate and he can black out because there’s not enough blood to circulate and be pumped to his head. Because of this, we never go into a hot tub.
If the water is too cold, the blood vessels in his legs constrict, his heart rate increases and he can black out from that as well. Walking in the pool is good; the pressure of the water forces the blood out of his feet and legs and into his circulation. My husband wears support hose. They are a pain to put on, but they prevent pooling of blood in his feet and legs.
My husband eats five small meals a day. Too much food all at once causes postprandial hypotension and he blacks out. He avoids coffee and tea because the caffeine is a diuretic; it makes him urinate and decreases his circulating fluid volume. The caffeine can also speed up his heart rate.
My husband drinks 6 to 8 glasses of water a day. If he did not keep up with his fluids, he’d black out. Some MSA patients do NOT sweat, but my husband sweats profusely. He can lose a lot of fluid if he sweats, especially if it’s hot. How much extra fluid does he drink? It’s a guess. I weigh my husband every day.
If he’s losing weight (3 to 5 pounds in a day), his blood pressure is low, and his heart rate is fast, he needs more fluid (think dehydration). If he’s gaining weight (3 to 5 pounds a day), his supine pressure is too high, and his legs are puffy, he needs less fluid.
I’ve learned not to use drugs called beta-blockers, such as propranolol (Inderal). Beta blockers are “wonder” drugs: they lower blood pressure, control rapid heart rates, decrease tremor (a problem in my husband), and relieve migraine headaches. But beta blockers dramatically drop his blood pressure.
I’ve also learned not to use drugs called calcium channel blockers: drugs that dilate arteries and improve circulation. While I want to improve my husband ’s circulation, the calcium channel blockers can dramatically drop his blood pressure. My husband has learned NOT to drink alcohol.
Alcohol dilates the blood pressure, and in my husband one drink is enough to cause him to black out. I know of people with MSA and PD who can and do drink in moderation. The watchword is caution.