title: [Does fasting influence preload responsiveness in ASA 1 and 2 volunteers?]
abstract: BACKGROUND
  Preoperative fasting was long regarded as an important cause of fluid depletion, leading to hemodynamic instability during surgery should replenishment not be promptly instituted. Lately, this traditional point of view has been progressively challenged, and a growing number of authors now propose a more restrictive approach to fluid management, although doubt remains as to the true hemodynamic influence of preoperative fasting.
  
  
  METHODS
  We designed an observational, analytic, prospective, longitudinal study in which 31 ASA 1 and ASA 2 volunteers underwent an echocardiographic examination both before and after a fasting period of at least 6h. Data from both static and dynamic preload indices were obtained on both periods, and subsequently compared.
  
  
  RESULTS
  Static preload indices exhibited a markedly variable behaviour with fasting. Dynamic indices, however, were far more consistent with one another, all pointing in the same direction, i.e., evidencing no statistically significant change with the fasting period. We also analysed the reliability of dynamic indices to respond to known, intentional preload changes. Aortic velocity time integral (VTI) variation with the passive leg raise manoeuvre was the only variable that proved to be sensitive enough to consistently signal the presence of preload variation.
  
  
  CONCLUSIONS
  Fasting does not appear to cause a change in preload of conscious volunteers nor does it significantly alter their position in the Frank-Starling curve, even with longer fasting times than usually recommended. Transaortic VTI variation with the passive leg raise manoeuvre is the most robust dynamic index (of those studied) to evaluate preload responsiveness in spontaneously breathing patients.
authors.affiliation: Centro Hospitalar de Lisboa Ocidental, Lisboa, Portugal. Electronic address: daniel_r_alves@sapo.pt.
authors.forename: Daniel Rodrigues
authors.initials: DR
authors.lastname: Alves
authors.affiliation: Centro Hospitalar de Lisboa Ocidental, Lisboa, Portugal.
authors.forename: Regina
authors.initials: R
authors.lastname: Ribeiras
mesh_terms: D000328:Adult; D000368:Aged; D004452:Echocardiography; D005215:Fasting; D005260:Female; D005440:Fluid Therapy; D006304:Health Status; D064368:Healthy Volunteers; D006439:Hemodynamics; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care; D011446:Prospective Studies
keywords: Echocardiography; Ecocardiografia; Fasting; Fluid therapy; Fluidoterapia; Hemodinâmica; Hemodynamics; Jejum