title: Measurement of gastric emptying in the critically ill.
abstract: OBJECTIVE
  Enteral nutrition is important in critically ill patients and is usually administered via a nasogastric tube. As gastric emptying is frequently delayed, and this compromises the delivery of nutrient, it is important that the emptying rate can be quantified.
  
  
  METHODS
  A comprehensive search of MEDLINE/PubMed, of English articles, from inception to 1 July 2014. References of included manuscripts were also examined for additional studies.
  
  
  RESULTS
  A number of methods are available to measure gastric emptying and these broadly can be categorised as direct- or indirect-test and surrogate assessments. Direct tests necessitate visualisation of the stomach contents during emptying and are unaffected by liver or kidney metabolism. The most frequently used direct modality is scintigraphy, which remains the 'gold standard'. Indirect tests use a marker that is absorbed in the proximal small intestine, so that measurements of the marker, or its metabolite measured in plasma or breath, correlates with gastric emptying. These tests include drug and carbohydrate absorption and isotope breath tests. Gastric residual volumes (GRVs) are used frequently to quantify gastric emptying during nasogastric feeding, but these measurements may be inaccurate and should be regarded as a surrogate measurement. While the inherent limitations of GRVs make them less suitable for research purposes they are often the only technique that is available for clinicians at the bedside.
  
  
  CONCLUSIONS
  Each of the available techniques has its strength and limitations. Accordingly, the choice of gastric emptying test is dictated by the particular requirement(s) and expertise of the investigator or clinician.
authors.affiliation: Discipline of Acute Care Medicine, University of Adelaide, South Australia, Australia; Intensive Care Unit, Royal Adelaide Hospital, South Australia, Australia. Electronic address: p_kar@hotmail.com.
authors.forename: Palash
authors.initials: P
authors.lastname: Kar
authors.affiliation: Centre for Research Excellence, University of Adelaide, South Australia, Australia; Discipline of Medicine, University of Adelaide, South Australia, Australia.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Jones
authors.affiliation: Centre for Research Excellence, University of Adelaide, South Australia, Australia; Discipline of Medicine, University of Adelaide, South Australia, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Horowitz
authors.affiliation: Discipline of Acute Care Medicine, University of Adelaide, South Australia, Australia; Intensive Care Unit, Royal Adelaide Hospital, South Australia, Australia; Centre for Research Excellence, University of Adelaide, South Australia, Australia.
authors.forename: Marianne J
authors.initials: MJ
authors.lastname: Chapman
authors.affiliation: Discipline of Acute Care Medicine, University of Adelaide, South Australia, Australia; Intensive Care Unit, Royal Adelaide Hospital, South Australia, Australia; Centre for Research Excellence, University of Adelaide, South Australia, Australia.
authors.forename: Adam M
authors.initials: AM
authors.lastname: Deane
mesh_terms: D019325:3-O-Methylglucose / Q000493:pharmacokinetics; D000082:Acetaminophen / Q000493:pharmacokinetics; D001944:Breath Tests; D016638:Critical Illness / Q000628:therapy*; D016208:Databases, Factual; D004750:Enteral Nutrition / Q000379:methods; D005746:Gastric Emptying; D005753:Gastric Mucosa / Q000378:metabolism; D005766:Gastrointestinal Contents; D006801:Humans; D008279:Magnetic Resonance Imaging; D014463:Ultrasonography
chemical_list: D019325:3-O-Methylglucose; D000082:Acetaminophen
keywords: Critically ill; Enteral nutrition; Gastric emptying; Intensive care