Table 1.

Studies comparing mixed venous oxygen saturation and central venous oxygen saturation

Study	Design and subjects	Results	Conclusions
Varpula and colleagues [14]	n = 16; septic shock; ICU; 72 paired samples	Mean SvO2 below mean ScvO2 at all time points; bias of difference 4.2% 95% limits of agreement -8.1 to 16.5%; difference correlated with CI and DO2	Difference between ScvO2 and SvO2 varied highly; SvO2 cannot be estimated on basis of ScvO2
Martin and colleagues [16]	n = 7; 580 comparative measurements; critically ill patients; ICU; with and without interventions	Difference ≥5% in 49% during periods of stability and in 50% during periods with therapeutic interventions	ScvO2 monitoring not reliable
Chawla and colleagues [17]	n = 32 postsurgical and n = 21 medical; ICU	SvO2 consistently lower than ScvO2 with mean (± SD) bias -5.2 ± 5.1%	SvO2 and ScvO2 not equivalent; substitution of ScvO2 for SvO2 in calculation of VO2 resulted in unacceptably large errors
Kopterides and colleagues [18]	n = 37; septic shock	Mean SvO2 below mean ScvO2; mean bias -8.5% 95% limits of agreement -20.2 to 3.3%; this resulted in higher VO2 values	ScvO2 and SvO2 not equivalent in ICU patients with septic shock; substitution of ScvO2 for SvO2 in calculation of VO2 resulted in unacceptably large errors
Ho and colleagues [19]	n = 20; cardiogenic or septic shock	ScvO2 overestimated SvO2 with mean bias 6.9%; 95% limits of agreement -5.0 to 18.8%; changes of ScvO2 and SvO2 did not follow the line of perfect agreement	ScvO2 and SvO2 are not interchangeable numerically
van Beest and colleagues [20]	n = 53; 265 paired samples; sepsis; ICU; multicentre	Mean SvO2 below mean ScvO2 at all time points; bias of difference 1.7% 95% limits of agreement -12.1 to 15.5%; identical results for change in ScvO2 and SvO2 Distribution of (ScvO2 - SvO2) (<0 vs. ≥0) similar in survivors and nonsurvivors	ScvO2 does not reliably predict SvO2 in patients with sepsis Trend of ScvO2 not superior in this context ScvO2 - SvO2 ≥0 not associated with improved outcome
Scheinmann and colleagues [21]	n = 24; critically ill cardiac patients; CCU	ScvO2 levels in superior vena cava are greater than SvO2 in shock (58 ± 13 vs. 47.5 ± 15; r = 0.55); changes in ScvO2 reflect changes in SvO2 (r = 0.90); ScvO2 from right atrium is similar to SvO2 (49.2 ± 19 vs. 49.2 ± 19; r = 0.96)	SvO2 consistently lower than ScvO2 Poor correlation in heart failure or shock Changes in ScvO2 reflect changes in SvO2
Dueck and colleagues [25]	n = 70; 502 comparative sets; neurosurgery	95% limits of agreement ranged from 6.8% to 9.3% for single values Correlations between changes of SvO2 and ScvO2: r = 0.755, P <0.001	Numerical ScvO2 values not equivalent to SvO2 in varying haemodynamic conditions; trend of ScvO2 may be substituted for the trend of SvO2
Reinhart and colleagues [26]	n = 32; critically ill patients; ICU; continuous parallel measurements	ScvO2 closely paralleled SvO2, in vitro r = 0.88 and in vivo r = 0.81 ScvO2 averaged (± SD) 7 ± 4% higher than SvO2 ScvO2 changed in parallel in 90% when SvO2 changed more than 5%	Continuous fibreoptic measurement of ScvO2 Potentially reliable tool to rapidly warn of acute change in the oxygen supply/demand ratio
Ladakis and colleagues [28]	n = 31 surgical and n = 30 medical; critically ill patients; ICU	Significant difference between mean ScvO2 and SvO2 (69.4 ± 1.1 vs. 68.6 ± 1.2%); r = 0.945 for total population	ScvO2 and SvO2 are closely related and interchangeable for initial evaluation
Tahvanainen and colleagues [29]	n = 42; critically ill patients; ICU; ScvO2 as representative of real changes in pulmonary shunt	Significant correlation between measured variables between PA blood samples and both superior vena cava and right atrial blood samples (P <0.001)	ScvO2 can replace SvO2; exact SvO2 value can only be measured from the PA itself

CCU, cardiac care unit; CI, cardiac index; DO₂, oxygen delivery; PA, pulmonary artery; ScvO₂, central venous oxygen saturation; SvO₂, mixed venous oxygen saturation; VO₂, oxygen consumption.