title: Assessment of stroke volume index with three different bioimpedance algorithms: lack of agreement compared to thermodilution.
abstract: OBJECTIVE
  The accuracy of bioimpedance stroke volume index (SVI) is questionable as studies report inconsistent results. It remains unclear whether the algorithms alone are responsible for these findings. We analyzed the raw impedance data with three algorithms and compared bioimpedance SVI to transpulmonary thermodilution (SVI(TD)).
  
  
  METHODS
  Prospective observational clinical study in a university hospital.
  
  
  METHODS
  Twenty adult patients scheduled for coronary artery bypass grafting (CABG).
  
  
  METHODS
  SVI(TD) and bioimpedance parameters were simultaneously obtained before surgery (t1), after bypass (t2), after sternal closure (t3), at the intensive care unit (t4), at normothermia (t5), after extubation (t6) and before discharge (t7). Bioimpedance data were analyzed off-line using cylinder (Kubicek: SVI(K); Wang: SVI(W)) and truncated cone based algorithms (Sramek-Bernstein: SVI(SB)).
  
  
  RESULTS
  Bias and precision between the SVI(TD) and SVI(K), SVI(SB), and SVI(W) was 1.0+/-10.8, 9.8+/-11.4, and -15.7+/-8.2 ml/m2 respectively, while the mean error was abundantly above 30%. Analysis of data per time moment resulted in a mean error above 30%, except for SVI(W) at t2 (28%).
  
  
  CONCLUSIONS
  Estimation of SVI by cylinder or truncated cone based algorithms is not reliable for clinical decision making in patients undergoing CABG surgery. A more robust approach for estimating bioimpedance based SVI may exclude inconsistencies in the underlying algorithms in existing thoracic bioimpedance cardiography devices.
authors.affiliation: Division of Perioperative and Emergency Care, University Medical Center, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands. e.e.c.dewaal@azu.nl
authors.forename: Eric E C
authors.initials: EE
authors.lastname: de Waal
authors.forename: Maurits K
authors.initials: MK
authors.lastname: Konings
authors.forename: Cor J
authors.initials: CJ
authors.lastname: Kalkman
authors.forename: Wolfgang F
authors.initials: WF
authors.lastname: Buhre
mesh_terms: D000465:Algorithms; D002307:Cardiography, Impedance / Q000379:methods*; D001026:Coronary Artery Bypass; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care; D011446:Prospective Studies; D015203:Reproducibility of Results; D013318:Stroke Volume; D013815:Thermodilution