title: Assessment of changes in cardiac index and fluid responsiveness: a comparison of Nexfin and transpulmonary thermodilution.
abstract: BACKGROUND
  The Nexfin device uses non-invasive photoplethysmography to monitor cardiac output and respiratory variations in pulse pressure and stroke volume. The aim of this study was to compare rapid changes in cardiac index after fluid challenge between Nexfin and bolus transpulmonary thermodilution and the ability to predict fluid responsiveness of dynamic indices given by Nexfin.
  
  
  METHODS
  Simultaneous comparative cardiac index were collected from transpulmonary thermodilution and Nexfin before and after fluid challenge in 45 patients following conventional cardiac surgery. Correlations, Bland-Altman analyses and percentage errors were calculated. Pulse pressure variations and stroke volume variations before fluid challenge were collected to assess their discrimination in predicting fluid responsiveness.
  
  
  RESULTS
  Eight (18%) patients were excluded. A weak positive relationship was found between rapid changes in cardiac index after fluid challenge given by both technologies (n = 37, r = 0.39, P = 0.019). Bias, precision and limits of agreements were 0.20 l/min/m(2) (95% confidence interval (CI) 0.02-0.40), 0.57 l/min/m(2) and ± 1.12 l/min/m(2) before fluid challenge, and 0.01 l/min/m(2) (95% CI -0.24 to 0.26), 0.74 l/min/m(2) and ± 1.45 l/min/m(2) after fluid challenge. Percentage errors between Nexfin and transpulmonary thermodilution were 55% and 58% before and after fluid challenge, respectively. Pulse pressure variations and stroke volume variations given by Nexfin were not discriminant to predict fluid responsiveness: areas under receiver operating characteristics curves 0.57 (95% CI 0.40-0.73) and 0.50 (0.33-0.67), respectively.
  
  
  CONCLUSIONS
  The Nexfin cannot be used to measure rapid changes in cardiac index following fluid challenge and to predict fluid responsiveness after cardiac surgery.
authors.affiliation: Department of Anesthesiology and Critical Care, CHU de Caen, Caen, France. fischer-mo@chu-caen.fr
authors.forename: M-O
authors.initials: MO
authors.lastname: Fischer
authors.forename: J
authors.initials: J
authors.lastname: Coucoravas
authors.forename: J
authors.initials: J
authors.lastname: Truong
authors.forename: L
authors.initials: L
authors.lastname: Zhu
authors.forename: J-L
authors.initials: JL
authors.lastname: Gérard
authors.forename: J-L
authors.initials: JL
authors.lastname: Hanouz
authors.forename: J-L
authors.initials: JL
authors.lastname: Fellahi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D001794:Blood Pressure; D001830:Body Surface Area; D002302:Cardiac Output; D006348:Cardiac Surgical Procedures; D002315:Cardiopulmonary Bypass; D003422:Critical Care / Q000379:methods*; D023381:Endpoint Determination; D005260:Female; D005440:Fluid Therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D017156:Photoplethysmography / Q000295:instrumentation*; D011182:Postoperative Care / Q000295:instrumentation / Q000379:methods*; D011237:Predictive Value of Tests; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013318:Stroke Volume; D013815:Thermodilution / Q000379:methods*; D016896:Treatment Outcome