Citation: Diabetes Forecast, July 1992 v45 n7 p70(5) ----------------------------------------------------------------- Title: The diabetes complication no one talks about. (autonomic neuropathy) (includes related article) Authors: Vinik, Aaron I.; Vinik, Etta ----------------------------------------------------------------- Subjects: Diabetes_Complications Diabetic neuropathies_Physiological aspects Nervous system, Autonomic_Diseases Reference #: A12349112 ================================================================= Full Text COPYRIGHT American Diabetes Association Inc. 1992 One diabetes complication that is less talked about than any of the others is autonomic neuropathy. That's not surprising. Autonomic neuropathy can make you unable to control urination and can contribute to diarrhea and constipation. Daily, basic parts of your life can become not just awkward but extremely troublesome. For some people, talking about it is almost as hard as living with it. Because this nerve disease is often ignored, people who have diabetes often don't learn about it or understand how it can be treated. But confronting and understanding the disease will help you down the road. Taking the time to learn about autonomic neuropathy may help you minimize its effects on your body if you develop it later. And if you've already developed this condition, understanding it will make an already tough job a little easier. Does Autonomic Mean Automatic? The word autonomic refers to something that your body does automatically, without you being aware of it happening. For instance, you do not have to tell your lungs to inhale and exhale or tell your heart to beat, yet these activities happen over and over, every day, and are vital to life. Of course, these activities are important: If your heart did not beat, you would die. Body functions like these are controlled by the autonomic nervous system, which also is known as the involuntary or subconscious nervous system. The autonomic nervous system is made up of nerves that control not only the heart and lungs, but also the intestines, blood vessels, stomach, bladder, and the sex organs. In fact, all the organs of the body have an autonomic nerve supply. Damage to these nerves is called autonomic neuropathy and it usually occurs progressively over time rather than all at once. In some cases, people whose nerves are damaged don't even know it. This is referred to as silent neuropathy. When autonomic neuropathy goes undetected or untreated, it can have serious consequences. That's why it helps to know how autonomic neuropathy affects the different systems of the body, how it can be diagnosed, and how it is treated. The Cardiovascular System Autonomic nerve damage often first appears in the cardiovascular system. One of the earliest warning signs is called tachycardia, a quickening of the heart that is not caused by infection, anxiety, stress, or thyroid disease. Tachycardia means that the heart is going too fast for the body's resting state. You recognize this as palpitations or pounding of your heart in your chest. In this condition, if any demands are made on the body, such as unusual exercise, it will not be able to cope. If you are experiencing tachycardia and have nerve damage to your heart, your heart will not pump blood throughout your body as it should. The tissues of your body then receive an insufficient supply of oxygen, because oxygen is carried by the blood. If you try to exercise with insufficient oxygen, you may become short of breath and even go into heart failure. Two systems of nerves affecting the heart are the vagus nerve system, which is part of the parasympathetic nerve system that slows the heartbeat down, and the sympathetic nerve system, which speeds up the heartbeat. When autonomic nerve damage affects these nerve systems, the heartbeat settles at a fixed rate that does not speed up when needed, such as during exercise, and does not slow down when appropriate, such as when you are napping. A continuous level of increased heart rate will likely tire the heart out quickly and may cause premature death. Incidentally, another way of understanding the difference between the parasympathetic and the sympathetic nervous systems is that the sympathetic nervous system is responsible for the "fight or flight" response. This makes you alert, widens your pupils, and speeds up your heart and reaction time. The parasympathetic system, on the other hand, governs languor, relaxation, and sleep. Nerve damage to the cardiovascular system can also affect your body's ability to control blood pressure and heart rate when you breathe, stand up, lie down, or move around. For people with diabetes, such damage is potentially dangerous. If you suddenly stand up, you may feel dizzy. You may think it is caused by low blood sugar, but it could be due to a momentary case of low blood pressure, because the act of suddenly standing up causes blood to flow to the feet and away from the head. Taking insulin won't help in this situation. Instead, remember to stand up slowly, especially if you are getting out of a bath. And take your required insulin shots lying down. People with diabetes may also be susceptible to what is known as orthostatic hypotension, or, as some call it, the "double whammy." When the autonomic nerves of the heart and the blood system are damaged, then your blood pressure can go up at night when you're sleeping and drop when you're standing during the day. Again, remember to stand up slowly when you get out of bed. Take warm baths, not hot ones, because hot baths increase the flow of blood to the skin and increase the risk of orthostatic hypotension. Elastic stockings that go up to the thigh also can help direct blood flow to the heart and brain. You may be able to prevent a rise in blood pressure at night by elevating the head of your bed. And if your symptoms are particularly severe, then your doctor may prescribe medications. Nerve damage can also affect your body's ability to transmit heart-related pain sensations to the brain. The lack of pain sensation can be catastrophic if it keeps you from taking appropriate measures. For instance, as many as one-third of the people with autonomic nerve damage who have a heart attack do not experience pain due to the attack. In people with this condition, changes in their electrocardiogram tests or in the level of enzymes that are released when their hearts are damaged may signal serious heart problems. Remember, if for no apparent reason you become short of breath, your ankles begin to swell, or you feel unusually tired and lethargic, see your doctor. You may have had a "silent" heart attack. The Stomach And Intestinal Tract One of the most serious and common kinds of autonomic nerve disease is called gastroparesis, which affects the nerves of the stomach. Gastroparesis can be found in about 25 percent of people with diabetes. It results from the inability of the stomach to move or propel food through the body's digestive system. Different foods move through your body at different rates, with liquids passing through the quickest and some solid foods, like complex carbohydrates and fatty foods, the slowest. As with other types of nerve disease, the symptoms of gastroparesis may be so mild that they go unnoticed for several years. Your doctor may not notice the condition unless you are having difficulty coordinating the peak action of your insulin with the arrival of food in your blood stream. In fact, your diabetes control may become "brittle," or fluctuate up and down in a way that is unrelated to the timing or dose of your insulin. As the condition progresses, you may experience bloating, nausea, and vomiting, and you may feel full even after eating small meals. Some people say they can taste on their breath a meal that they ate two or three days before, or that when they vomit they find undigested food eaten more than one meal before. Gastroscopy, an examination of the stomach with an instrument called an endoscope, is one way a doctor can tell if the cause of gastroparesis is an inflammation or a tumor, rather than due to diabetes. Your doctor may also suggest a special X-ray. If these methods don't provide answers, your doctor may ask you to eat a meal that includes a small, relatively harmless amount of radioactive dye that can be traced as it works its way through your digestive tract. To treat gastroparesis, your doctor may recommend changing your diet or using medications. Doctors frequently begin treatment by suggesting a change in eating habits, such as eating six or more small meals in liquid form. Foods that are low in fat and dietary fiber are helpful because fat slows down the stomach's digestive process and fiber is difficult to digest. As for treatment with drugs, metoclopramide (Reglan) is available for gastroparesis treatment, and a few others are being studied. All these drugs increase stomach contractions, and they are usually taken about 30 minutes before a meal or snack. Some drugs for gastroparesis can cause sleepiness or drowsiness, and the body tends to become resistant to their effects. Also, your doctor may prescribe erythromycin, an antibiotic commonly used for infections that also stimulates the stomach to empty. Another condition associated with autonomic nerve disease is diarrhea, which may be found in about 20 percent of people with diabetes. Diarrhea is sometimes caused by damage to the propulsive nerves of the intestine. Food remains in the intestine longer than it should, causing constipation at first. But the work of bacteria on the food later leads to diarrhea. Diarrhea can also be caused by damage to the intestinal nerves or the loss of digestive enzymes from the pancreas. Your doctor may eliminate other causes of diarrhea by measuring the amount of hydrogen in your breath, or by examining your stool for parasites or undigested food particles and doing special X-rays of the bowel. To treat diarrhea due to diabetes, your doctor may prescribe an antibiotic to eliminate bacteria. But diarrhea can be difficult to treat and your doctor may try other drugs as well. Try to avoid drugs that cause constipation. They make matters worse. Constipation is the most frequent complaint of people with autonomic neuropathy. It affects about 25 percent of people with diabetes and about 50 percent of those with neuropathy. Constipation is usually treated in one of two ways. First, consuming plenty of water may be all that is required. Second, psyllium, a drug that works as a fecal softener, may be be prescribed, or other drugs that can help in the functioning of the large bowel. If the bowel is obstructed because of impacted feces, an enema may be necessary. The Bladder And Urinary System Both the urinary bladder and the sphincter muscle near the anus are regulated by the autonomic nervous system. The urinary bladder is the reservoir that collects urine, from about one to one-and-a-half cups a day, until a convenient time to pass it out of your system. Most healthy people don't have to worry about uncontrolled urination, because the sphincter muscle contracts, stopping any leakage. People who have diabetes may have damage to the nerves in the urinary system and may suffer from incontinence, or uncontrolled urinating. If the nerves to your bladder are damaged, you may lose the ability to sense that your bladder is filling up, and you may have trouble spontaneously emptying it. This can contribute to disease, because as urine accumulates, the bladder distends, or expands, and may become susceptible to infection. You may urinate less frequently, and the overflow of excess urine can lead to incontinence--dribbling and wetting oneself. Your doctor may recommend an ultrasound test to determine the size, shape, and position of your bladder. A more complicated test is the eystometrogram, in which a catheter is placed into the bladder through the urethra. Water is then slowly poured into your bladder through the catheter to find out how full your bladder must be before you feel the urge to urinate. Treating bladder problems usually requires that you urinate every three to four hours during the day, even though you don't feel the need to urinate because of lack of bladder sensation. After urinating, press downwards on the lower abdomen, to help empty the bladder. This will let you know if your bladder still contains any urine. It will also help remove any accumulation of urine in the bladder and prevent bladder infections. Some medicines, such as bethanechol, can help the contraction of your bladder. In addition, you may want to test your urine with special strips to be sure there are no bacteria present in your urine. If your nerve damage is so extensive that the bladder no longer responds to physical measures such as these, then periodic self-catheterization may help. This process involves placing a tube into the urethra and up into the bladder to allow it to drain. Although this may sound difficult, self-eatheterization is a skill that many people use to treat their bladder problems. Diagnosing Autonomic Neuropathy Autonomic neuropathy is usually diagnosed by measuring the heart rate. A resting heart rate of more than 100 beats per minute suggests damaged parasympathetic nerves. Other conditions, however, that speed up the heart heat and imitate autonomic neuropathy, such as infection, fever, injury, or thyroid disease, must be excluded. Autonomic neuropathy of the sympathetic nervous system is usually diagnosed by measuring someone's blood pressure changes when they shift from a lying down to a standing up position. Decreases in blood pressure that are much greater than normal may indicate orthostatic hypotension and damaged sympathetic nerves. Diabetes Control And Nutrition Controlling your diabetes is an important way of protecting your nerves from damage caused by high blood glucose levels. Avoiding alcohol and cigarettes will help, as well. If your autonomic nerve disease is already severe, however, tight blood glucose control is not for you. When your nerves are damaged, you may be unable to detect the usual signs of hypoglycemia (low blood glucose levels) such as tingling sensations around the mouth or an increased heartbeat. Therefore, your doctor may recommend that you avoid trying to rigidly control your diabetes, if achieving that control increases your risk of hypoglycemia. The "Orphan" Of Complications Because autonomic neuropathy tends to be ignored, it has been called the orphan of diabetes complications. This condition can bring much suffering, and it can even cause sudden death. With a better understanding of autonomic neuropathy, however, you will be better able to lead an active life, one that is free of many of the worries that accompany the condition. And with more information, you may also be able to take steps now that can save your life later. Aaron I. Vinik, MD, PhD, is director of the Diabetes Research Institute in Norfolk, Va. Etta Vinik, M.4, is associate director of the Diabetes Education Institute of Eastern Virginia Medical School in Norfolk, Va. Research Avenues One approach to treat autonomic neuropathy being studied involves using drugs called aldose reductase inhibitors. These drugs block the accumulation of sugar alcohols, such as sorbitol and fructose, in nerve tissues. Because researchers are still studying the safety and effectiveness of these drugs, aldose reductase inhibitors are not available over the counter. Some researchers are also studying a drug called aminoguanidine. In animals, this drug decreases the accumulation of substances known as advanced glycosylation end products (AGE). These substances accumulate in the tissue, causing glucose molecules to attach to protein molecules, leading to tissue damage. In the future we may be able to use treatments that prevent autoimmune nerve destruction, in which the body turns against its own nerve system. We also may make progress in using nerve growth factors, or substances that allow nerves to regrow even if they are injured by diabetes. You may wish to ask your doctor if you are a candidate for research studies, and, if so, how to participate in them. --AARON I. VINIK AND ETTA VINIK =================================================================