title: Stroke volume averaging for individualized goal-directed fluid therapy with oesophageal Doppler.
abstract: BACKGROUND
  An individualized fluid optimization strategy, based on maximization of cardiac stroke volume (SV) with colloid boluses (goal-directed therapy), improves outcome after surgery. Oesophageal Doppler (OD) is used for SV maximization in most randomized studies, but evidence-based guidelines for the SV maximization procedure are lacking and variation in SV may influence the indication for fluid administration. We measured beat-to-beat OD SV before and after fluid optimization in order to estimate the number of heartbeats for which SV needs to be averaged to provide an acceptable accuracy for goal-directed therapy with this technology.
  
  
  METHODS
  Twenty patients scheduled for surgery were anaesthetized, followed by OD SV assessment. Thirty seconds of beat-to-beat data were recorded before and after volume optimization performed by successive boluses of 200 ml colloid until SV did not increase >or=10%. SV variability was assessed before and after the volume optimization when SV was measured beat to beat and when it was averaged over 2-10 heartbeats.
  
  
  RESULTS
  Nineteen (95%) and 17 (85%) patients demonstrated an SV variability >or=10% before and after volume optimization, respectively, when SV was measured beat to beat. However, when SV was averaged over 10 heartbeats, only two (10%) and one (5%) of the patients demonstrated an SV variability >or=10% before and after optimization, respectively (P<0.0001).
  
  
  CONCLUSIONS
  OD SV variability is significantly reduced and reaches an acceptable level when SV is averaged over 10 heartbeats. The use of a shorter averaging period for SV may lead to incorrect volume administration in goal-directed fluid management.
authors.affiliation: Section of Surgical Pathophysiology, Rigshospitalet, Copenhagen, Denmark.
authors.forename: C C
authors.initials: CC
authors.lastname: Jørgensen
authors.forename: M
authors.initials: M
authors.lastname: Bundgaard-Nielsen
authors.forename: L T
authors.initials: LT
authors.lastname: Skovgaard
authors.forename: N H
authors.initials: NH
authors.lastname: Secher
authors.forename: H
authors.initials: H
authors.lastname: Kehlet
mesh_terms: D000328:Adult; D000368:Aged; D004947:Esophagus / Q000000981:diagnostic imaging* / Q000601:surgery; D005260:Female; D005440:Fluid Therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D013318:Stroke Volume; D018608:Ultrasonography, Doppler