title: Glucose absorption and gastric emptying in critical illness.
abstract: BACKGROUND
  Delayed gastric emptying occurs frequently in critically ill patients and has the potential to adversely affect both the rate, and extent, of nutrient absorption. However, there is limited information about nutrient absorption in the critically ill, and the relationship between gastric emptying (GE) and absorption has hitherto not been evaluated. The aim of this study was to quantify glucose absorption and the relationships between GE, glucose absorption and glycaemia in critically ill patients.
  
  
  METHODS
  Studies were performed in nineteen mechanically-ventilated critically ill patients and compared to nineteen healthy subjects. Following 4 hours fasting, 100 ml of Ensure, 2 g 3-O-methyl glucose (3-OMG) and 99mTc sulphur colloid were infused into the stomach over 5 minutes. Glucose absorption (plasma 3-OMG), blood glucose levels and GE (scintigraphy) were measured over four hours. Data are mean +/- SEM. A P-value < 0.05 was considered significant.
  
  
  RESULTS
  Absorption of 3-OMG was markedly reduced in patients (AUC240: 26.2 +/- 18.4 vs. 66.6 +/- 16.8; P < 0.001; peak: 0.17 +/- 0.12 vs. 0.37 +/- 0.098 mMol/l; P < 0.001; time to peak; 151 +/- 84 vs. 89 +/- 33 minutes; P = 0.007); and both the baseline (8.0 +/- 2.1 vs. 5.6 +/- 0.23 mMol/l; P < 0.001) and peak (10.0 +/- 2.2 vs. 7.7 +/- 0.2 mMol/l; P < 0.001) blood glucose levels were higher in patients; compared to healthy subjects. In patients; 3-OMG absorption was directly related to GE (AUC240; r = -0.77 to -0.87; P < 0.001; peak concentrations; r = -0.75 to -0.81; P = 0.001; time to peak; r = 0.89-0.94; P < 0.001); but when GE was normal (percent retention240 < 10%; n = 9) absorption was still impaired. GE was inversely related to baseline blood glucose, such that elevated levels were associated with slower GE (ret 60, 180 and 240 minutes: r > 0.51; P < 0.05).
  
  
  CONCLUSIONS
  In critically ill patients; (i) the rate and extent of glucose absorption are markedly reduced; (ii) GE is a major determinant of the rate of absorption, but does not fully account for the extent of impaired absorption; (iii) blood glucose concentration could be one of a number of factors affecting GE.
authors.affiliation: Department of Anaesthesia and Intensive Care, Royal Adelaide Hospital, North Terrace, Adelaide, SA 5000, Australia. marianne.chapman@health.sa.gov.au
authors.forename: Marianne J
authors.initials: MJ
authors.lastname: Chapman
authors.forename: Robert J L
authors.initials: RJ
authors.lastname: Fraser
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Matthews
authors.forename: Antonietta
authors.initials: A
authors.lastname: Russo
authors.forename: Max
authors.initials: M
authors.lastname: Bellon
authors.forename: Laura K
authors.initials: LK
authors.lastname: Besanko
authors.forename: Karen L
authors.initials: KL
authors.lastname: Jones
authors.forename: Ross
authors.initials: R
authors.lastname: Butler
authors.forename: Barry
authors.initials: B
authors.lastname: Chatterton
authors.forename: Michael
authors.initials: M
authors.lastname: Horowitz
mesh_terms: D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism*; D016638:Critical Illness; D019422:Dietary Sucrose / Q000008:administration & dosage / Q000378:metabolism; D004750:Enteral Nutrition; D005260:Female; D005526:Food, Formulated; D005746:Gastric Emptying / Q000502:physiology*; D038321:Glycemic Index; D006151:Guanosine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D013671:Technetium Tc 99m Sulfur Colloid / Q000008:administration & dosage
chemical_list: D001786:Blood Glucose; D019422:Dietary Sucrose; C037626:3'-O-methylguanosine; C082131:Ensure formulated food; D006151:Guanosine; D013671:Technetium Tc 99m Sulfur Colloid