title: Use of the refractometer as a tool to monitor dietary formula concentration in gastric juice.
abstract: OBJECTIVE
  Critically ill patients do not always tolerate nasogastric tube feeding. Gastric residual volumes are widely used to evaluate feeding tolerance, but controversy exists about what constitutes the residual volume (diet formula or digestive juice). In this paper, we describe the use of the refractometer as a tool to monitor dietary formula concentration in gastric juice and evaluate gastric juice refractometry as a possible clinical application.
  
  
  METHODS
  Brix value (an index of the total solutes in solution) readings for polymeric diet at pH 1, 4, 7 and 8, and at 4 degrees C, 25 degrees C and 37 degrees C, and in fasting gastric juice were determined with a refractometer.
  
  
  RESULTS
  We found that distilled water, minerals, and vitamins had low Brix values of 0+/-0, 1.2+/-0.1, and 0.4+/-0.1, respectively. On the other hand, because carbohydrate (17 g/100 ml), protein (5.3 g/100 ml), fat (4.1 g/100 ml), and full-strength polymeric diet had high concentrations of dissolved nutrients, they also had high Brix values (12.1+/-0.6, 6.5+/-0.1, 6.0+/-0.1, and 23.5+/-0.1, respectively). The Brix values of polymeric diet had a linear additive relationship with the diet formula concentration at various pHs, temperatures, and in the gastric juice.
  
  
  CONCLUSIONS
  Brix value measurement can be used to monitor stomach dietary formula concentration. Such information can be obtained at the bedside and used to evaluate feeding-intolerant patients receiving enteral feeding.
authors.affiliation: Department of Internal Medicine, Division of Gastroenterology, Tri-Service General Hospital, National Defense Medical Center, Taiwan, Republic of China.
authors.forename: W-K
authors.initials: WK
authors.lastname: Chang
authors.forename: M-Z
authors.initials: MZ
authors.lastname: Chen
authors.forename: Y-C
authors.initials: YC
authors.lastname: Chao
mesh_terms: D003422:Critical Care / Q000379:methods*; D016638:Critical Illness; D004750:Enteral Nutrition; D005526:Food, Formulated / Q000032:analysis*; D005746:Gastric Emptying; D005750:Gastric Juice / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007441:Intubation, Gastrointestinal / Q000009:adverse effects; D012031:Refractometry / Q000379:methods*; D013696:Temperature