title: Mesenteric blood flow, glucose absorption and blood pressure responses to small intestinal glucose in critically ill patients older than 65 years.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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).
  
  
  RESULTS
  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 [AUC(120-180): 4.571 (2.591, 6.551) versus 11.307 (8.447, 14.167) mmol/l min; P < 0.001 and AUC(120-240): 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 AUC(120-180) and ∆SMA flow at t (150): r (2) = 0.29; P < 0.05).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Discipline of Acute Care Medicine, University of Adelaide, North Terrace, Adelaide, SA, Australia. jennifer.sim@student.adelaide.edu.au
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Sim
authors.forename: M
authors.initials: M
authors.lastname: Horowitz
authors.forename: M J
authors.initials: MJ
authors.lastname: Summers
authors.forename: L G
authors.initials: LG
authors.lastname: Trahair
authors.forename: R S
authors.initials: RS
authors.lastname: Goud
authors.forename: A V
authors.initials: AV
authors.lastname: Zaknic
authors.forename: T
authors.initials: T
authors.lastname: Hausken
authors.forename: J D
authors.initials: JD
authors.lastname: Fraser
authors.forename: M J
authors.initials: MJ
authors.lastname: Chapman
authors.forename: K L
authors.initials: KL
authors.lastname: Jones
authors.forename: A M
authors.initials: AM
authors.lastname: Deane
mesh_terms: D000368:Aged; D001794:Blood Pressure; D016638:Critical Illness; D005260:Female; D005947:Glucose / Q000008:administration & dosage* / Q000378:metabolism*; D006801:Humans; D007408:Intestinal Absorption; D007421:Intestine, Small; D008297:Male; D008643:Mesentery / Q000098:blood supply*; D012039:Regional Blood Flow
chemical_list: D005947:Glucose