title: Measurement of cardiac output before and after cardiopulmonary bypass: Comparison among aortic transit-time ultrasound, thermodilution, and noninvasive partial CO2 rebreathing.
abstract: OBJECTIVE
  A noninvasive continuous cardiac output system (NICO) has been developed recently. NICO uses a ratio of the change in the end-tidal carbon dioxide partial pressure and carbon dioxide elimination in response to a brief period of partial rebreathing to measure CO. The aim of this study was to compare the agreement among NICO, bolus (TDCO), and continuous thermodilution (CCO), with transit-time flowmetry of the ascending aorta using an ultrasonic flow probe (UFP) before and after cardiopulmonary bypass (CPB).
  
  
  METHODS
  Prospective, observational human study.
  
  
  METHODS
  Veterans Affairs Medical Center Hospital.
  
  
  METHODS
  Sixty-eight patients.
  
  
  METHODS
  Matched sets of CO measurements between NICO, TDCO, CCO, and UFP were collected in 68 patients undergoing elective CABG at specific time periods before and after separation from CPB. After anesthetic induction, all patients had an NICO sensor attached between the endotracheal tube and the breathing circuit, a PAC floated into the pulmonary artery for TDCO and CCO monitoring, and a UFP positioned on the ascending aorta and used for the reference CO. Bland-Altman analysis was used to compare the agreement among the different methods.
  
  
  RESULTS
  Bland-Altman analysis of CO measurements before CPB yielded a bias, precision, and percent error of 0.04 L/min +/- 1.07 L/min (44.8%) for NICO, 0.18 L/min +/- 1.01 L/min (41.7%) for TDCO, and 0.29 L/min +/- 1.40 L/min (57.5%) for CCO compared with simultaneous UFP CO measurements, respectively. After separation from CPB (average 29 mins), bias, precision, and percent error were -0.46 L/min +/- 1.06 L/min (37.3%) for NICO, 0.35 L/min +/- 1.39 L/min (46.1%) for TDCO, and 0.36 L/min +/- 1.96 L/min (64.7%) for CCO compared with UFP CO measurements, respectively.
  
  
  CONCLUSIONS
  Before initiation of CPB, the accuracy for all 3 techniques was similar. After separation from CPB, the tendency was for NICO to underestimate CO and for TDCO and CCO to overestimate it. NICO offers an alternative to invasive CO measurement.
authors.affiliation: Department of Anesthesiology, University of Florida College of Medicine and the Gainesville Veterans Affairs Medical Center, Gainesville, FL, USA. botero@anest1.anest.ufl.edu
authors.forename: Monica
authors.initials: M
authors.lastname: Botero
authors.forename: David
authors.initials: D
authors.lastname: Kirby
authors.forename: Emilio B
authors.initials: EB
authors.lastname: Lobato
authors.forename: Edward D
authors.initials: ED
authors.lastname: Staples
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Gravenstein
mesh_terms: D000280:Administration, Inhalation; D000368:Aged; D000369:Aged, 80 and over; D000768:Anesthesia, General / Q000379:methods; D001011:Aorta / Q000000981:diagnostic imaging*; D002245:Carbon Dioxide; D002302:Cardiac Output / Q000502:physiology*; D002315:Cardiopulmonary Bypass / Q000379:methods*; D055590:Electromagnetic Phenomena / Q000379:methods; D006801:Humans; D007442:Intubation, Intratracheal / Q000379:methods; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D011446:Prospective Studies; D015203:Reproducibility of Results; D012121:Respiration, Artificial / Q000379:methods; D012212:Rheology / Q000379:methods; D013815:Thermodilution / Q000379:methods; D013997:Time Factors; D014463:Ultrasonography
chemical_list: D002245:Carbon Dioxide