title: Central and mixed venous blood oxygen correlate well during acute normovolemic hemodilution in anesthetized pigs.
abstract: BACKGROUND
  Central venous oxygen saturation (ScvO2) and oxygen tension (PcvO2), obtained from the superior vena cava, correlate well with mixed venous (pulmonary arterial) oxygen saturation (SvO2) and tension (pvO2) when the hematocrit is normal. The present study was undertaken to assess whether extreme hemodilution affects this relation.
  
  
  METHODS
  We compared mixed and central venous blood during graded arterial desaturation (inspired fraction of oxygen (FIO2) between 1.0 and 0.10) in 10 hemodiluted pigs, and in 10 pigs with normal hematocrit (control), during fentanyl-ketamine-pancuronium anesthesia and mechanical ventilation.
  
  
  RESULTS
  Arterial oxygen saturation decreased from 100% at FIO2 = 1.0 to 44 +/- 12% at FIO2 = 0.10 (mean +/- SD). Venous oxygen saturation ranged from 3.5% to 97.3%. The regression coefficient between SvO2 and ScvO2 was 0.97 (R2 = 0.93, bias -2.4 +/- 5.8%) in the hemodiluted and 0.99 (R2 = 0.97, bias -3.0 +/- 5.0%) in the control group. Venous oxygen tension values ranged from 0.5 kPa to 9.5 kPa, and the regression coefficient for oxygen tension was 0.94 (R2 = 0.89, bias -0.20 +/- 0.47 kPa) in the hemodiluted and 0.99 (R2 = 0.97, bias -0.43 +/- 0.48 kPa) in the control group. The regression coefficient for pH was 0.95 in the hemodiluted and 0.98 in the control animals.
  
  
  CONCLUSIONS
  The findings indicate that also during hemodilution monitoring of central venous blood oxygen may be as useful as monitoring of mixed venous blood oxygen.
authors.affiliation: Department of Anesthesia and Intensive Care, University Hospital, Lund, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Schou
authors.forename: V
authors.initials: V
authors.lastname: Perez de Sá
authors.forename: A
authors.initials: A
authors.lastname: Larsson
mesh_terms: D000758:Anesthesia; D000818:Animals; D006438:Hemodilution; D006863:Hydrogen-Ion Concentration; D010100:Oxygen / Q000097:blood*; D013552:Swine; D014680:Veins
chemical_list: D010100:Oxygen