Dear Doctor: I am an 86-year-old female, and sometimes, about an hour after eating a meal, my blood pressure drops significantly, from a normal of 123/74 to as low as 93/47. When it happens, my lips tingle and get dry, and I feel "zonked" out, like I'm in some kind of a trance. What causes this? What can I do?
Dear Reader: What you've described is known as postprandial hypotension, which means that someone's blood pressure drops measurably in response to eating. (Postprandial refers to the time after a meal, and the "hypo" in hypotension refers to low blood pressure.) The condition is common in older adults and is estimated to be present to some degree in up to 30 to 40 percent of the elderly. It is also often found in people living with Parkinson's disease. Because the condition can lead to dizziness, falls and fainting, and in some cases can result in angina, stroke or heart attack, it's important that it be diagnosed and addressed.
Each time we eat, we require our circulatory system to reorganize and recalibrate its activities. That's because the tasks of digestion and absorption create the need for additional blood flow to the stomach, particularly the small intestine. To accommodate that need, blood vessels throughout the body that are not involved in the digestive system begin to narrow. This allows blood to be redirected to the stomach and small intestine, while still maintaining consistent blood pressure throughout the body. To aid in those dual goals, the heart beats faster. As the stomach and intestines complete their work, blood vessels dilate again, and the heartbeat returns to normal.
In people with postprandial hypotension, blood flows as needed to the digestive organs. However, the circulatory system doesn't respond with the appropriate measures. For reasons that aren't yet clear, the heart rate doesn't increase enough, and blood vessels do not narrow enough to compensate for the redirected blood flow. That results in a drop in blood pressure and the symptoms you described.
Since low blood pressure can lead to a loss of consciousness and a fall, as well as the more serious complications we mentioned earlier, it's important that you address this with your family doctor. It sounds as though you've been tracking your blood pressure with a home monitor, and your doctor will want to see those readings. She or he will also want to follow up with a definitive diagnosis, which entails a baseline blood pressure reading before a meal, and then up to two hours of post-meal blood pressure monitoring.
People who take blood pressure medications may be asked to make changes to how and when they take the drug. But please don't make any changes without your physician's input.
Lifestyle changes may include a pre-meal cup of coffee, as caffeine can cause an increase in blood pressure. A large glass of water before a meal has also been shown to be helpful. Diet may play a role too, as postprandial hypotension has been linked to meals high in carbohydrates. It's a good idea to track what you're eating and see if the food correlates to episodes of low blood pressure.
(Send your questions to email@example.com, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)