title: Comparison of non-calibrated pulse-contour analysis with continuous thermodilution for cardiac output assessment in patients with induced hypothermia after cardiac arrest.
abstract: OBJECTIVE
  Induced mild hypothermia after cardiac arrest interferes with clinical assessment of the cardiovascular status of patients. In this situation, non-invasive cardiac output measurement could be useful. Unfortunately, arterial pulse contour is altered by temperature, and the performance of devices using arterial blood pressure contour analysis to derive cardiac output may be insufficient.
  
  
  METHODS
  Mild hypothermia (32-34°C) was induced in eight patients after out-of-hospital cardiac arrest and successful resuscitation. Cardiac output (CO) was measured simultaneously by continuous thermodilution using a pulmonary artery catheter and a cardiac output monitor (Vigilance II, Edwards Lifesciences) and by pulse contour analysis using an arterial line and the Vigileo monitor (Edwards Lifesciences) during both normothermia (>36°C) and hypothermia. Continuous CO from both monitors was compared (Bland-Altman) and concordance of changes measured in consecutive 8-min intervals was measured.
  
  
  RESULTS
  Mean cardiac output was 3.9±1.2 l/min during hypothermia and 6.1±2.6 l/min during normothermia (p<0.001). During hypothermia (normothermia), bias was 0.23 (0.77)l/min, precision (1 SD) was 0.6 (0.72) l/min, and the limits of agreement were -1.06 to 1.51 (-0.64 to 2.18) l/min, corresponding to a percentage error of ±34% (±24%). Concordance of directional CO changes >10% was 53.9% in hypothermia and 51.4% in normothermia.
  
  
  CONCLUSIONS
  Induced hypothermia was not associated with increased bias or limits of agreement for the comparison of Vigileo and continuous thermodilution, but percentage error was high during normothermia and increased further during hypothermia. Less than 50% of clinically relevant CO changes during hypothermia were concordant.
authors.affiliation: Department of Intensive Care Medicine, Bern University Hospital and University of Bern, Inselspital, Freiburgstrasse, 3010 Bern, Switzerland. matthias.haenggi@insel.ch
authors.forename: Matthias
authors.initials: M
authors.lastname: Haenggi
authors.forename: Daniel
authors.initials: D
authors.lastname: Barthelmes
authors.forename: Hanno
authors.initials: H
authors.lastname: Ulmer
authors.forename: Jukka
authors.initials: J
authors.lastname: Takala
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Jakob
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002302:Cardiac Output / Q000502:physiology*; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006323:Heart Arrest / Q000503:physiopathology* / Q000628:therapy; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007036:Hypothermia, Induced; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D011674:Pulse / Q000379:methods; D015203:Reproducibility of Results; D013815:Thermodilution / Q000379:methods