Submitted on April 20, 2009
Revised on June 8, 2009
Accepted on June 22, 2009
Comparative effects of oral and intraduodenal glucose on blood pressure, heart rate and splanchnic blood flow in healthy older subjects
Diana Gentilcore1, Nivasinee S Nair2, Lora Vanis1, Christopher K Rayner3, James H. Meyer, Trygve Hausken, Michael Horowitz4, and Karen L. Jones4*
1 University of Adelaide, Royal Adelaide Hospital
2 University of Adelaide Discipline of Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia
3 Royal Adelaide Hospital
4 University of Adelaide
* To whom correspondence should be addressed. E-mail: karen.jones{at}adelaide.edu.au.
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 (5M, 3F, age 66-75yrs) were studied on two occasions. On day 1, each subject ingested 300ml water containing 75g glucose; GE was quantified by three-dimensional ultrasonography between t=0-120 minutes and the rate of emptying (kcal min-1) 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±0.1 kcal/min. Systolic BP (P<0.01), SMA flow (P<0.05) and blood glucose (P<0.01) were greater and HR less (P<0.01) after oral, when compared with intraduodenal, glucose. There were comparable falls in diastolic BP during the study days (P<0.01 for both). We conclude that the magnitude of the fall in systolic BP and rise in HR are less after oral, when compared to intraduodenal, glucose presumably reflecting the 'protective' effect of gastric distension.
