title: Can mixed venous hemoglobin oxygen saturation be estimated using a NICO monitor?
abstract: BACKGROUND
  We hypothesized that mixed venous hemoglobin oxygen saturation (SvO2) can be estimated by calculation from CO2 production, cardiac output, and arterial oxygen saturation measured using a noninvasive cardiac output (NICO) monitor (Novametrix-Respironics, Wallingford, CT).
  
  
  METHODS
  Twenty-three patients undergoing aortic aneurysm repair underwent SvO2 monitoring using a pulmonary artery catheter and cardiac output monitoring using a NICO monitor. The estimated SvO2 value calculated from NICO monitor-derived values was compared with the SvO2 value measured using a pulmonary artery catheter. The accuracy of this estimation was analyzed with Bland-Altman method. The ability of this estimation to track the change of SvO2 was also evaluated using correlation analysis to compare the changes of estimated SvO2 and measured SvO2.
  
  
  RESULTS
  The bias +/- limits of agreement of the estimated SvO2 against measured SvO2 was -2.1% +/- 11.2%. The change of estimated SvO2 was modestly correlated with the change of measured SvO2.
  
  
  CONCLUSIONS
  SvO2 derived from the values measured by the NICO monitor cannot be used interchangeably with the values measured spectrophotometrically using the pulmonary artery catheter. More refinement is required to obtain more reliable estimate of SvO2 less invasively. However, large changes of SvO2 may be detected with this method and can be used as a precautionary sign when the balance between oxygen supply and demand is compromised without inserting a central venous catheter.
authors.affiliation: Department of Anesthesiology, Toho University Medical Center Ohmori Hospital, 6-11-1, Ohmori-nishi, Ohta, Tokyo 143-8541, Japan. ykotake@med.toho-u.ac.jp
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Kotake
authors.forename: Takashige
authors.initials: T
authors.lastname: Yamada
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Nagata
authors.forename: Takeshi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Junzo
authors.initials: J
authors.lastname: Takeda
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002245:Carbon Dioxide / Q000097:blood; D002302:Cardiac Output / Q000502:physiology*; D005260:Female; D006454:Hemoglobins / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation* / Q000379:methods*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology; D011446:Prospective Studies
chemical_list: D006454:Hemoglobins; D002245:Carbon Dioxide; D010100:Oxygen