Comparative effects of oral and intraduodenal glucose on blood pressure, heart rate, and splanchnic blood flow in healthy older subjects

Abstract

Gentilcore D, Nair NS, Vanis L, Rayner CK, Meyer JH, Hausken T, Horowitz M, Jones KL. Comparative effects of oral and intraduodenal glucose on blood pressure, heart rate, and splanchnic blood flow in healthy older subjects. Am J Physiol Regul Integr Comp Physiol 297: R716 -R722, 2009. First published June 24, 2009 doi:10.1152/ajpregu.00215.2009.-Postprandial hypotension occurs frequently, particularly in the elderly. The magnitude of the fall in blood pressure (BP) and rise in heart rate (HR) in response to enteral glucose are greater when gastric emptying (GE) or small intestinal infusion are more rapid. Meal ingestion is associated with an increase in splanchnic blood flow. In contrast, gastric distension may attenuate the postprandial fall in BP. The aims of this study were to evaluate, in older subjects, the comparative effects of intraduodenal glucose infusion, at a rate similar to GE of oral glucose, on BP, HR, superior mesenteric artery (SMA) flow, and blood glucose. Eight healthy subjects (5 men, 3 women, age 66 -75 yr) were studied on two occasions. On day 1, each subject ingested 300 ml of water containing 75 g glucose. GE was quantified by three-dimensional ultrasonography between time t ϭ 0 -120 min, and the rate of emptying (kcal/min) was calculated. On day 2, glucose was infused intraduodenally at the same rate as that on day 1. On both days, BP, HR, SMA flow, and blood glucose were measured. The mean GE of oral glucose was 1.3 Ϯ 0.1 kcal/min. Systolic BP (P Ͻ 0.01), SMA flow (P Ͻ 0.05), and blood glucose (P Ͻ 0.01) were greater and HR less (P Ͻ 0.01) after oral, compared with intraduodenal, glucose. There were comparable falls in diastolic BP during the study days (P Ͻ 0.01 for both). We conclude that the magnitude of the fall in systolic BP and rise in HR are less after oral, compared with intraduodenal, glucose, presumably reflecting the "protective" effect of gastric distension. postprandial hypotension; gastric emptying; three-dimensional and Doppler ultrasound POSTPRANDIAL HYPOTENSION, defined as a decrease in systolic blood pressure Ն20 mmHg, occurring within 2 h of the end of a meal (23,25,38,39), is an important clinical problem, most commonly affecting the elderly and patients with autonomic dysfunction, the latter often secondary to diabetes (23,25,38,39). Postprandial hypotension is associated with significant complications, including syncope and falls (25) and, in some cases, stroke and angina (1,25,51).The stomach is likely to modulate the hypotensive response to a high-carbohydrate meal in two ways, first, by controlling the rate at which glucose enters the small intestine. Our laboratory's studies in healthy older subjects (26, 42) and patients with type 2 diabetes (28, 46) have established that there is a direct relationship between the magnitude of the fall in systolic blood pressure with the rate of small intestinal delivery of glucose (26,28,41,42), a response that depends on the total load of glucose entering the duodenum independent of glucose concentration (11,27). When glu...

Effects of variations in intragastric volume on blood pressure and splanchnic blood flow during intraduodenal glucose infusion in healthy older subjects

“…It is, accordingly, likely that a "threshold" volume and/or pressure needs to be exceeded for a reduction in SMA blood flow, and this is Ͼ500 ml. The relationship between the magnitude of the fall in blood pressure and rise in SMA blood flow is consistent with previous observations (11,46) and with the concept that the latter is integral to the hypotensive response. While gastric distension has been shown to elevate MVR in the cat (25), to our knowledge this is the first study to evaluate the effects of variations in intragastric volume on MVR in humans.…”

“…Meal ingestion (11) and small intestinal nutrient infusion (9,46,47) increase superior mesenteric artery (SMA) blood flow, which may be important in mediating the postprandial hypotensive response (24) and can be measured by Doppler techniques (33). Information about the effects of gastric distension on SMA blood flow in animals and humans is limited and inconsistent, ranging from no effect (43) to increases (11,25,43) and decreases (30,43,46).…”

“…Information about the effects of gastric distension on SMA blood flow in animals and humans is limited and inconsistent, ranging from no effect (43) to increases (11,25,43) and decreases (30,43,46).…”

Comparative effects of glucose and water drinks on blood pressure and cardiac function in older subjects with and without postprandial hypotension

“…That the fall in BP is less following oral, when compared with an identical duodenal, glucose load, in healthy older subjects is likely to reflect the “protective” effects of gastric distension (Gentilcore et al. 2009). In addition to the paucity of information about cardiac function in PPH, no studies have evaluated both the hypotensive response to oral carbohydrate and the pressor response to water drinking in patients with PPH.…”

Functional Ultrasound of the Gastrointestinal Tract

“…The fall in systolic blood pressure and rise in heart rate induced by an oral glucose load was less compared with glucose infused intraduodenally at a comparable rate, presumably reflecting the loss of ''protective'' factors related to gastric distension (Gentilcore et al 2009). Effects of gastric distension on blood pressure and SMA blood flow responses to intraduodenal glucose were then measured in eight healthy older subjects using barostat for gastric distension and duplex ultrasonography for flow measurements (Vanis et al 2010).…”