title: Uncalibrated pulse power analysis fails to reliably measure cardiac output in patients undergoing coronary artery bypass surgery.
abstract: BACKGROUND
  Uncalibrated arterial pulse power analysis has been recently introduced for continuous monitoring of cardiac index (CI). The aim of the present study was to compare the accuracy of arterial pulse power analysis with intermittent transpulmonary thermodilution (TPTD) before and after cardiopulmonary bypass (CPB).
  
  
  METHODS
  Forty-two patients scheduled for elective coronary surgery were studied after induction of anaesthesia, before and after CPB respectively. Each patient was monitored with the pulse contour cardiac output (PiCCO) system, a central venous line and the recently introduced LiDCO monitoring system. Haemodynamic variables included measurement of CI derived by transpulmonary thermodilution (CITPTD) or CI derived by pulse power analysis (CIPP), before and after calibration (CIPPnon-cal., CIPPcal.). Percentage changes of CI (ΔCITPTD, ΔCIPPnon-cal./PPcal.) were calculated to analyse directional changes.
  
  
  RESULTS
  Before CPB there was no significant correlation between CIPPnon-cal. and CITPTD (r2 = 0.04, P = 0.08) with a percentage error (PE) of 86%. Higher mean arterial pressure (MAP) values were significantly correlated with higher CIPPnon-cal. (r2 = 0.26, P < 0.0001). After CPB, CIPPcal. revealed a significant correlation compared with CITPTD (r2 = 0.77, P < 0.0001) with PE of 28%. Changes in CIPPcal. (ΔCIPPcal.) showed a correlation with changes in CITPTD (ΔCITPTD) only after CPB (r2 = 0.52, P = 0.005).
  
  
  CONCLUSIONS
  Uncalibrated pulse power analysis was significantly influenced by MAP and was not able to reliably measure CI compared with TPTD. Calibration improved accuracy, but pulse power analysis was still not consistently interchangeable with TPTD. Only calibrated pulse power analysis was able to reliably track haemodynamic changes and trends.
authors.affiliation: Department of Anaesthesiology and Intensive Care Medicine, University Hospital Schleswig-Holstein, Campus Kiel, Schwanenweg 21, 24105 Kiel, Germany. broch@anaesthesie.uni-kiel.de
authors.forename: Ole
authors.initials: O
authors.lastname: Broch
authors.forename: Jochen
authors.initials: J
authors.lastname: Renner
authors.forename: Jan
authors.initials: J
authors.lastname: Höcker
authors.forename: Matthias
authors.initials: M
authors.lastname: Gruenewald
authors.forename: Patrick
authors.initials: P
authors.lastname: Meybohm
authors.forename: Jan
authors.initials: J
authors.lastname: Schöttler
authors.forename: Markus
authors.initials: M
authors.lastname: Steinfath
authors.forename: Berthold
authors.initials: B
authors.lastname: Bein
mesh_terms: D000328:Adult; D000368:Aged; D002138:Calibration; D002302:Cardiac Output / Q000502:physiology*; D001026:Coronary Artery Bypass; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D011182:Postoperative Care; D011300:Preoperative Care; D011674:Pulse / Q000379:methods*; D015203:Reproducibility of Results; D013815:Thermodilution / Q000379:methods*