Mesenteric blood flow, glucose absorption and blood pressure responses to small intestinal glucose in critically ill patients older than 65 years
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To compare nutrient-stimulated changes in superior mesenteric artery (SMA) blood flow, glucose absorption and glycaemia in individuals older than 65 years with, and without, critical illness.
Following a 1-h ‘observation’ period (t 0–t 60), 0.9 % saline and glucose (1 kcal/ml) were infused directly into the small intestine at 2 ml/min between t 60–t 120, and t 120–t 180, respectively. SMA blood flow was measured using Doppler ultrasonography at t 60 (fasting), t 90 and t 150 and is presented as raw values and nutrient-stimulated increment from baseline (Δ). Glucose absorption was evaluated using serum 3-O-methylglucose (3-OMG) concentrations during, and for 1 h after, the glucose infusion (i.e. t 120–t 180 and t 120–t 240). Mean arterial pressure was recorded between t 60–t 240. Data are presented as median (25th, 75th percentile).
Eleven mechanically ventilated critically ill patients [age 75 (69, 79) years] and nine healthy volunteers [70 (68, 77) years] were studied. The magnitude of the nutrient-stimulated increase in SMA flow was markedly less in the critically ill when compared with healthy subjects [Δt 150: patients 115 (−138, 367) versus health 836 (618, 1,054) ml/min; P = 0.001]. In patients, glucose absorption was reduced during, and for 1 h after, the glucose infusion when compared with health [AUC120–180: 4.571 (2.591, 6.551) versus 11.307 (8.447, 14.167) mmol/l min; P < 0.001 and AUC120–240: 26.5 (17.7, 35.3) versus 40.6 (31.7, 49.4) mmol/l min; P = 0.031]. A close relationship between the nutrient-stimulated increment in SMA flow and glucose absorption was evident (3-OMG AUC120–180 and ∆SMA flow at t 150: r 2 = 0.29; P < 0.05).
In critically ill patients aged >65 years, stimulation of SMA flow by small intestinal glucose infusion may be attenuated, which could account for the reduction in glucose absorption.
KeywordsCritical illness Superior mesenteric artery Glucose absorption Nutrition Postprandial hypotension Splanchnic blood flow
Sodium glucose luminal transporter-1
Superior mesenteric artery
Mean arterial blood pressure
The study was supported by a NHMRC project grant (1025648). Ms. Jennifer Sim was supported by a Florey Honours Bachelor of Medical Sciences 2011 Scholarship, and Dr. Adam Deane was supported by a Sylvia and Charles Viertel Charitable Foundation Clinical Investigatorship. We acknowledge the guidance of Ms. Kylie Lange regarding appropriate statistical testing.
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