title: Dynamic indices do not predict volume responsiveness in routine clinical practice.
abstract: BACKGROUND
  Dynamic indices, including pulse pressure, systolic pressure, and stroke volume variation (PPV, SPV, and SVV), are accurate predictors of fluid responsiveness under strict conditions, for example, controlled mechanical ventilation using conventional tidal volumes (TVs) in the absence of cardiac arrhythmias. However, in routine clinical practice, these prerequisites are not always met. We evaluated the effect of regularly used ventilator settings, different calculation methods, and the presence of cardiac arrhythmias on the ability of dynamic indices to predict fluid responsiveness in sedated, mechanically ventilated patients.
  
  
  METHODS
  We prospectively evaluated 47 fluid challenges in 29 consecutive cardiac surgery patients. Patients were divided into different groups based on TV. Dynamic indices were calculated in various ways: calculation over 30 s, breath-by-breath (with and without excluding arrhythmias), and with correction for TV.
  
  
  RESULTS
  The predictive value was optimal in the group ventilated with TVs >7 ml kg(-1) with correction for TV, calculated breath-by-breath, and with exclusion of arrhythmias [area under the curve (AUC)=0.95, 0.93, and 0.90 for PPV, SPV, and SVV, respectively]. Including patients ventilated with lower TVs decreased the predictive value of all dynamic indices, while calculating dynamic indices over 30 s and not excluding cardiac arrhythmias further reduced the AUC to 0.51, 0.63, and 0.51 for PPV, SPV, and SVV, respectively.
  
  
  CONCLUSIONS
  PPV, SPV, and SVV are the only reliable predictors of fluid responsiveness under strict conditions. In routine clinical practice, factors including low TV, cardiac arrhythmias, and the calculation method can substantially reduce their predictive value.
authors.affiliation: MIRA--Institute for Biomedical Technology and Technical Medicine, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands. b.lansdorp@utwente.nl
authors.forename: B
authors.initials: B
authors.lastname: Lansdorp
authors.forename: J
authors.initials: J
authors.lastname: Lemson
authors.forename: M J A M
authors.initials: MJ
authors.lastname: van Putten
authors.forename: A
authors.initials: A
authors.lastname: de Keijzer
authors.forename: J G
authors.initials: JG
authors.lastname: van der Hoeven
authors.forename: P
authors.initials: P
authors.lastname: Pickkers
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000503:physiopathology; D002302:Cardiac Output / Q000502:physiology; D016292:Procedural Sedation / Q000379:methods; D001026:Coronary Artery Bypass; D005260:Female; D005440:Fluid Therapy / Q000379:methods*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D011182:Postoperative Care / Q000379:methods*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods; D013990:Tidal Volume / Q000502:physiology