title: Noninvasive continuous cardiac output by the Nexfin before and after preload-modifying maneuvers: a comparison with intermittent thermodilution cardiac output.
abstract: BACKGROUND
  The Nexfin uses an uncalibrated pulse contour method for the continuous measurement of cardiac output (CO) in a totally noninvasive manner. Since the accuracy of pulse contour methods and their ability to track changes in CO have been repeatedly questioned, we have compared the CO measured by the Nexfin (NAPCO) with the CO measured by the pulmonary artery catheter (PACCO) in cardiosurgical patients before and after preload-modifying maneuvers.
  
  
  METHODS
  Twenty-eight patients who underwent on-pump cardiac surgery, of whom 18 were receiving vasopressor and/or inotropic therapy, were studied during the first postoperative hours. Preload modification, in the form of either a fluid challenge or a passive leg raising maneuver, was done whenever clinically indicated, with PACCO and NAPCO being simultaneously measured before and after each intervention.
  
  
  RESULTS
  A fluid challenge was administered to 22 patients, and the passive leg raising maneuver was performed in 6 patients. These interventions were repeated in 19 patients producing a total of 47 pairs of measurements. At baseline, mean (±SD) CO was 4.9 ± 1.1 and 5.0 ± 1.4 L·min(-1), for the PACCO and NAPCO, respectively, bias 0.1 ± 1.0, 95% prediction interval -2.5 to 2.4 L·min(-1), and 39% of error. After preload modification, the mean CO was 5.6 ± 1.3 and 5.6± 1.5 L·min(-1) for the PACCO and NAPCO, respectively, bias -0.0 ± 1.1, 95% prediction interval -2.6 to 2.7 L·min(-1), and 38% of error. The correlation coefficients (r) between the PACCO and NAPCO before and after preload modification were 0.71 (95% confidence interval [95% CI], 0.53-0.82) and 0.70 (95% CI, 0.52-0.82), respectively. Preload modification induced similar absolute changes in PACCO and NAPCO (r = 0.9, P < 0.0001). A 4-quadrant scatter plot showed a concordance rate of 100% (95% CI, 80.5%-100%) between the changes in NAPCO and PACCO. Polar plot analysis demonstrated a small polar angle and radial limits of agreement well below the 30° benchmark. The area under a receiver operating characteristic curve, testing the ability of Nexfin to detect an increase of ≥15% in PACCO, was 0.974 (95% CI, 0.93-0.99).
  
  
  CONCLUSIONS
  Although the Nexfin has limited accuracy when compared with the pulmonary artery catheter, it can reliably track preload-induced changes in CO in stable patients after cardiac surgery in the presence of moderate vasopressor and inotropic therapy. This ability, combined with its total noninvasiveness, fast installation, and ease of use, make the Nexfin a suitable monitor for the perioperative continuous measurement of CO. The reliability of this monitor in tracking the CO when significant changes in peripheral resistance take place still needs to be established.
authors.affiliation: 1-st Department of Cardiovascular Anaesthesiology and Intensive Care, Prof. C. C. Iliescu Institute for Cardiovascular Diseases, Bucharest, Romania. bubenek@alsys.ro
authors.forename: Serban Ion
authors.initials: SI
authors.lastname: Bubenek-Turconi
authors.forename: Mihaela
authors.initials: M
authors.lastname: Craciun
authors.forename: Ion
authors.initials: I
authors.lastname: Miclea
authors.forename: Azriel
authors.initials: A
authors.lastname: Perel
mesh_terms: D000368:Aged; D019540:Area Under Curve; D062186:Arterial Pressure; D015924:Blood Pressure Monitors; D002302:Cardiac Output / Q000187:drug effects; D006348:Cardiac Surgical Procedures; D002315:Cardiopulmonary Bypass; D002316:Cardiotonic Agents / Q000627:therapeutic use; D002407:Catheterization, Swan-Ganz; D004867:Equipment Design; D005260:Female; D005385:Fingers / Q000098:blood supply*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D016343:Monitoring, Intraoperative / Q000295:instrumentation*; D017711:Nonlinear Dynamics; D056888:Patient Positioning; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D012815:Signal Processing, Computer-Assisted; D016683:Supine Position; D013815:Thermodilution / Q000379:methods*; D013997:Time Factors; D014662:Vasoconstrictor Agents / Q000627:therapeutic use; D014882:Water-Electrolyte Balance
chemical_list: D002316:Cardiotonic Agents; D014662:Vasoconstrictor Agents