Pathophysiology of postprandial hypotension in the elderly - role of "gastric" and "small intestinal" mechanisms

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A fall in blood pressure after a meal (known as postprandial hypotension) is an important clinical problem, particularly in the elderly, occurring in ~50% of nursing home residents and ~30% of healthy older subjects. Postprandial hypotension is associated with a substantial increase in the incidence of falls, stroke, as well as mortality. The mechanisms responsible for the fall in blood pressure after a meal are not well understood, although changes in gastrointestinal blood flow and the release of gut hormones, have been implicated. While ingestion of carbohydrate, particularly glucose, has been reported to decrease blood pressure most potently, there is inadequate and conflicting information about the effects of other nutrients such as fat and protein. Current therapies are less than optimal. Studies by our research group have established that the fall in blood pressure in response to meals is related to the rate at which nutrients enter the small intestine ie the fall in blood pressure is greater when the stomach empties more quickly. In contrast, gastric distension reduces the fall in blood pressure. Hence, treatment could be directed at facilitating gastric distension and-or slowing the rate of nutrient delivery into the small intestine. Our previous studies have not included any assessment of changes in blood flow to the gut after meals, or of the interaction between gastric distension and small intestinal mechanisms, and have involved healthy older subjects and patients with type 2 (non-insulin dependent) diabetes rather than individuals with known postprandial hypotension. We now have the capacity to measure blood flow in the gut with ultrasound. The studies proposed in the current application represent a logical development from our previous work and have important implications for the management of postprandial hypotension.