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1668326 
Journal Article 
Lack of equivalence between central and mixed venous oxygen saturation 
Chawla, LS; Zia, H; Gutierrez, G; Katz, NM; Seneff, MG; Shah, M 
2004 
Yes 
Chest
ISSN: 0012-3692
EISSN: 1931-3543 
126 
6 
1891-1896 
15596689 
WOS:000225754900031 
Study objective: We compared paired samples of central venous O-2 saturation (Scvo(2)) and mixed venous O-2, saturation (S (v) over baro(2)) to test the hyothesis that Scvo(2) is equivalent to S (v) over baro(2). We also compared O-2 consumption No-2) computed with Scvo(2) (Vo(2)cv) to that computed with S (v) over baro(2). (Vo(2)v).



Design: Prospective, sequential, observational study.



Setting: Combined medical-surgical ICU.



Patients: Fifty-three individuals > 18 years of age of either sex who required a pulmonary artery catheter (PAC) to guide fluid therapy. Subjects were identified as postsurgical (32 patients) or medical (21 patients) according to their ICU admission diagnosis.



Interventions: A PAC was inserted through the internal jugular or subclavian veins. Care was taken to place the PAC proximal port approximately 3 cm above the tricuspid valve. Blood samples were drawn from the proximal and distal ports in random order. An arterial blood sample also was drawn.



Measurements: Cardiac output in triplicate, systemic pressure, and central pressure. We analyzed blood samples for hemoglobin concentration and O-2 saturation (So(2)). Data were compared by correlation analysis and by the method of Bland and Altman.



Results: S (v) over baro(2) was consistently lower than Scvo(2) (p < 0.0001), with a mean (+/- SD) bias of -5.2 +/- 5.1%. Similar differences in Scvo(2) and S (v) over baro(2) were present within each subgroup (p < 0.001). A lower S (v) over baro(2) resulted in Vo(2)v values that were higher than the Vo(2)cv values for all patients in the study (mean Vo(2)v, 236.7 +/- 103.4 mL/min; mean Vo(2)cv, 191.1 +/- 84.0 mL/min; p < 0.001) as well as for patients within each subgroup (p < 0.001).



Conclusions: Measurements of Scvo(2) and S (v) over baro(2) were not equivalent in this sample of critically ill patients. Moreover, substituting Scvo(2) for S (v) over baro(2) in the calculation of Vo(2) produced unacceptably large errors. The decrease in So(2) between Scvo(2) to S (v) over baro(2) may result from the rnixing of atrial and coronary sinus blood. As such, this difference may be a marker of myocardial O-2 consumption. 
central venous oxygenation; coronory sinus; mixed venous oxygenation; monitoring; myocardial metabiolism; oxygen consumption; oxygen delivery; pulmonary artery catheter; resuscitation