Free
Clinical Science  |   August 2005
Trends but Not Individual Values of Central Venous Oxygen Saturation Agree with Mixed Venous Oxygen Saturation during Varying Hemodynamic Conditions
Author Affiliations & Notes
  • Michael H. Dueck, M.D., D.E.A.A.
    *
  • Markus Klimek, M.D., D.E.A.A.
  • Stefan Appenrodt
  • Christoph Weigand, M.D.
    *
  • Ulf Boerner, M.D.
    §
  • * Staff Anesthesiologist, Department of Anesthesiology, ‡ Staff Otorhinolaryngologist, Department of Otolaryngology, § Professor of Anesthesiology and Intensive Care Medicine, University of Cologne. † Vice-Head of Department of Anesthesiology, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands.
Article Information
Clinical Science / Cardiovascular Anesthesia / Respiratory System
Clinical Science   |   August 2005
Trends but Not Individual Values of Central Venous Oxygen Saturation Agree with Mixed Venous Oxygen Saturation during Varying Hemodynamic Conditions
Anesthesiology 8 2005, Vol.103, 249-257. doi:
Anesthesiology 8 2005, Vol.103, 249-257. doi:
MIXED venous oxygen saturation (Svo2) monitoring is used as a surrogate for the balance between systemic oxygen delivery and consumption during the treatment of critically ill patients.1 However, measurement of Svo2requires placement of a pulmonary artery (PA) catheter with a risk-versus  -benefit relation that is still a matter of controversy.2–4 On the other hand, a central venous (CV) catheter is routinely inserted in critically ill patients for monitoring of CV pressure and administration of catecholamines and parenteral nutrition. Therefore, measurement of CV oxygen saturation (Scvo2) seems to be an attractive alternative to monitoring of Svo2because it can be performed more easily, is less risky, and is less costly.
In a recently published guideline, Svo2and Scvo2were declared as equivalent for the management of severe sepsis,5 although previous studies found contradictory results.6–25 It should be noted that the statistical approaches used in most of these investigations (e.g.  , correlation and regression analysis7,8,12–14,16) are questionable regarding the statistical evaluation of the agreement of two different methods.26,27 Furthermore, one has to differentiate between the analysis of single data points and the analysis of the change in oxygen saturation values over time (trend).
The aim of our study was to compare Svo2versus  Scvo2in various hemodynamic conditions. Because some previous studies only evaluated the agreement between Svo2and right atrial oxygen saturation (Srao2),10,17,18 we also compared Svo2versus  Srao2. The sitting position, which is used to perform neurosurgical operations in the cerebellum and the cerebellopontine angle, is known to induce hemodynamic changes compared with the supine position.28–30 Therefore, we prospectively studied the oxygen saturation of blood samples simultaneously taken during both the supine and the sitting position from the superior vena cava (SVC), right atrium (RA), and PA.
Materials and Methods
Subjects
After obtaining approval from the Institutional Review Board at the University of Cologne (Cologne, Germany) and informed consent from each participant, we studied 70 patients scheduled to undergo a neurosurgical procedure in the sitting position.
Anesthesia Protocol and Catheter Placement
Anesthesia was induced and maintained with intravenous fentanyl and midazolam. Monitoring included electrocardiography, intravascular blood pressure measurement, pulse oximetry, CV pressure monitoring, urine output monitoring, precordial Doppler ultrasound for detection of venous air embolism, and arterial blood gas analysis.
Multiorificed CV catheters (Vygon GmbH, Aachen, Germany) were inserted via  the right subclavian vein, and PA catheters (OptiQ®; Abbott, Chicago, IL) were inserted via  the right internal jugular vein using a standard aseptic technique. Intravascular electrocardiography (Alphacard®; Sterimed, Puettlingen, Germany) was used to confirm the placement of the CV catheters in the lower SVC directly above the caval–atrial junction. The PA catheters were positioned following standard procedures. When the wedge position was obtained, the catheters were withdrawn to place the proximal injectate port in the RA, which was confirmed by intravascular electrocardiography.
Blood Gas Analysis and Determination of Hemodynamic Variables
Blood samples were drawn simultaneously from the PA, RA, and SVC at four different time points: (1) in the supine position after induction of anesthesia (T1); (2) twice during the neurosurgical operation in the sitting position (T2 and T3); and (3) in the supine position after the neurosurgical procedure was finished (T4). A standard volume of 1.5 ml blood was obtained from each site (QS 50®; Radiometer, Copenhagen, Denmark) and cooled in ice water after withdrawal of dead space blood and flushing fluid. Three consecutive oxygen saturations per blood sample were determined photospectrometrically immediately after each series of blood samples (OSM 3 Hemoximeter; Radiometer). The average of these three measurements was calculated for each site and each time point and used for further statistical analysis. Immediately after a series of blood samples was drawn, mean arterial blood pressure (MAP), heart rate, and cardiac output (CO) were recorded. CO was determined by bolus thermodilution technique using the PA catheter connected to a CO computer (Q-Vue®; Abbott). To quantify the repeatability of the standard oxygen saturation measurement method, in 17 patients, an additional five replicate blood samples were drawn immediately one after the other from the PA.
Statistical Analysis
Based on unpublished data from our institution in a similar neurosurgical population, a power analysis was performed before the study, and it indicated that a sample size of 70 patients was necessary (α= 0.05, power = 0.80) to detect a difference of ±2% between Svo2and Scvo2, which was defined as the smallest clinically relevant difference. The anticipated SD was set at ±5%.
Repeatability
Each of the resulting five Svo2values per patient were subtracted from each other, resulting in n = 17 · 10 individual differences. In accordance with the recommendations of Bland and Altman,27 a one-way analysis of variance with subject as the factor was calculated for these 170 individual differences. The within-subject SD sw  was estimated as the square root of the residual mean square. Furthermore, a 95% repeatability coefficient was calculated as 1.96√2sw  (= 2.77sw  ), which is compared to the 95% limits of agreement between the different methods (see next section).
Statistical Analysis of Individual Values
The systematic error (bias) and the variability (SD of the bias) for Svo2versus  Scvo2and Svo2versus  Srao2were calculated. Bias was expressed as the mean of the differences of the individual values. The Student t  test was used to determine whether the mean differences were significantly different from zero, and Pearson correlation coefficients between Svo2and Scvo2and between Svo2and Srao2were determined. Furthermore, 95% limits of agreement were calculated as bias ± 1.96 SD. The differences between individual values were plotted against their means for each time point (Bland and Altman plot).26 
Statistical Analysis of Changes in Oxygen Saturation
For evaluating the agreement between the different sites of oxygen saturation measurement (Svo2vs.  Scvo2and Svo2vs.  Srao2) regarding the trend of values, a Pearson correlation coefficient was calculated for differences of oxygen saturation between sequential time points (T1–T2, T2–T3, T3–T4).
To quantify changes in hemodynamic variables, corresponding to the oxygen saturation measurements, differences between sequential time points were calculated for MAP, heart rate, and CO. Values are presented as mean ± SD unless otherwise stated. For all statistical procedures, a P  value less than 0.05 was considered significant. The Statistical Package for the Social Sciences (SPSS, release 11.0; SPSS Inc., Chicago, IL) was used for all calculations.
Results
Thirty-two male and 38 female patients with an average height of 170.0 ± 7.9 cm (range, 147–190 cm), weight of 76.1 ± 9.0 kg (40–120 kg), and age of 53.1 ± 8.8 yr (17–78 yr) were enrolled in the study. Five patients had an American Society of Anesthesiologists (ASA) physical status of I, 38 had an ASA physical status of II, 24 had an ASA physical status of III, and 3 had an ASA physical status of IV. Mean changes of hemodynamic variables between time points were as follows: MAP, 14.1 ± 9.6% (range, 2.4–42%); heart rate, 16.1 ± 16.0% (0–69.2%); and CO, 16.4 ± 14.3% (0–70%).
Evaluation of the agreement between different sites of oxygen saturation measurement requires knowledge about the repeatability of the oxygen saturation–measurement method itself.26 Oxygen saturation values from 17 · 5 replicate blood samples revealed a within-subject SD sw  of 1.05% and a repeatability coefficient of 2.91% (fig. 1).
Fig. 1. Bland and Altman plot of the differences between replicate mixed venous oxygen saturation (Svo2) measurements against their mean values. Five replicate blood samples were drawn in 17 patients. Each of the resulting five Svo2values per patient were subtracted from each other, resulting in n = 17 · 10 individual differences. The  broken line  indicates the mean difference, and  unbroken lines  indicate repeatability coefficient (mean ± within-subject SD  s  w). 
Fig. 1. Bland and Altman plot of the differences between replicate mixed venous oxygen saturation (Svo2) measurements against their mean values. Five replicate blood samples were drawn in 17 patients. Each of the resulting five Svo2values per patient were subtracted from each other, resulting in n = 17 · 10 individual differences. The  broken line  indicates the mean difference, and  unbroken lines  indicate repeatability coefficient (mean ± within-subject SD  s  w). 
Fig. 1. Bland and Altman plot of the differences between replicate mixed venous oxygen saturation (Svo2) measurements against their mean values. Five replicate blood samples were drawn in 17 patients. Each of the resulting five Svo2values per patient were subtracted from each other, resulting in n = 17 · 10 individual differences. The  broken line  indicates the mean difference, and  unbroken lines  indicate repeatability coefficient (mean ± within-subject SD  s  w). 
×
Regarding the comparison of different sampling sites, ideally 2 · 280 comparative pairs of measurements from 70 patients at four different time points could be made in our study. However, because of technical (incorrect position of catheter) or organizational reasons (duration of operation), 256 (Svo2vs.  Scvo2) and 246 (Svo2vs.  Srao2) comparative sets of measurements, respectively, were obtained (table 1). The mean Svo2was larger than the mean Scvo2and the mean Srao2at all time points (T1–T4). Changing from the supine position to the sitting position (from T1 to T2) resulted in an increase in mean differences (bias) in oxygen saturation (Svo2vs.  Scvo2and Svo2vs.  Srao2), whereas changing from the sitting position to the supine position (from T3 to T4) led to a decrease in bias (Svo2vs.  Scvo2and Svo2vs.  Srao2) (table 1). Only once did the bias in oxygen saturations exceed 2% (Svo2vs.  Scvo2; bias at T3 = 2.79%), which was defined as a clinically relevant threshold (table 1). Correlation coefficients ranged from 0.688 (Svo2vs.  Scvo2; T4) to 0.851 (Svo2vs.  Srao2; T2) (table 1).
Table 1. Mean Differences (Bias) and Correlation Coefficients in Oxygen Saturations of Blood Samples Taken from Various Sites 
Image not available
Table 1. Mean Differences (Bias) and Correlation Coefficients in Oxygen Saturations of Blood Samples Taken from Various Sites 
×
More important are the distributions of differences of individual values from various sites of measurement. Figure 2depicts the Bland and Altman plot for Svo2versus  Scvo2. Ninety-five percent limits of agreement for Svo2versus  Srao2are calculated as ±7.12% (T1), ±6.83% (T2), ±7.32% (T3), and ±6.58% (T4). Differences in oxygen saturations of 10% or greater were observed in individual patients at all time points T1–T4 for comparisons Svo2versus  Srao2and Svo2versus  Scvo2.
Fig. 2. Bland and Altman plots of the differences between mixed venous oxygen saturation (Svo2) and central venous oxygen saturation (Scvo2) at different time points. (  T1  ) Supine position after induction of anesthesia and insertion of catheters. (  T2  and  T3  ) During the neurosurgical procedure in the sitting position, with an interval of at least 1 h between. (  T4  ) Supine position after the neurosurgical procedure was completed. The  broken line  indicates the mean difference (bias), and  unbroken lines  indicate 95% limits of agreement (mean ± SD). Note the large 95% limits of agreement. 
Fig. 2. Bland and Altman plots of the differences between mixed venous oxygen saturation (Svo2) and central venous oxygen saturation (Scvo2) at different time points. (  T1  ) Supine position after induction of anesthesia and insertion of catheters. (  T2  and  T3  ) During the neurosurgical procedure in the sitting position, with an interval of at least 1 h between. (  T4  ) Supine position after the neurosurgical procedure was completed. The  broken line  indicates the mean difference (bias), and  unbroken lines  indicate 95% limits of agreement (mean ± SD). Note the large 95% limits of agreement. 
Fig. 2. Bland and Altman plots of the differences between mixed venous oxygen saturation (Svo2) and central venous oxygen saturation (Scvo2) at different time points. (  T1  ) Supine position after induction of anesthesia and insertion of catheters. (  T2  and  T3  ) During the neurosurgical procedure in the sitting position, with an interval of at least 1 h between. (  T4  ) Supine position after the neurosurgical procedure was completed. The  broken line  indicates the mean difference (bias), and  unbroken lines  indicate 95% limits of agreement (mean ± SD). Note the large 95% limits of agreement. 
×
Changes in oxygen saturation over time are presented in figure 3. Even when individual values were different, changes in Scvo2and Srao2paralleled changes in Svo2quantitatively, demonstrated by correlation coefficients of R  = 0.75 (Svo2vs.  Scvo2) and R  = 0.82 (Svo2vs.  Srao2), respectively (table 2). Considering more distinct changes in Svo2(> 5% and > 10%), correlation coefficients increased (table 2). All values of R  are highly significant (P  < 0.0001).
Fig. 3. Changes in mixed venous (ΔSvo2) and central venous oxygen saturation (ΔScvo2) between two measurements. n = 182;  r  = 0.755; equation of the regression line: ΔScvo2= 1.084 ×ΔSvo2+ 0.412. 
Fig. 3. Changes in mixed venous (ΔSvo2) and central venous oxygen saturation (ΔScvo2) between two measurements. n = 182;  r  = 0.755; equation of the regression line: ΔScvo2= 1.084 ×ΔSvo2+ 0.412. 
Fig. 3. Changes in mixed venous (ΔSvo2) and central venous oxygen saturation (ΔScvo2) between two measurements. n = 182;  r  = 0.755; equation of the regression line: ΔScvo2= 1.084 ×ΔSvo2+ 0.412. 
×
Table 2. Correlation of Changes in Oxygen Saturation of Blood Samples Taken from Different Sites 
Image not available
Table 2. Correlation of Changes in Oxygen Saturation of Blood Samples Taken from Different Sites 
×
Discussion
In the current study, the 95% limits of agreement between the standard Svo2method and both the Scvo2method and the Srao2method were large. In fact, some individual measurements of oxygen saturation of CV blood and RA blood differed more than 10% from corresponding mixed venous blood values. Therefore, an enormous variability was found between absolute values of Svo2and Scvo2and of Svo2and Srao2, respectively, suggesting that individual values of Scvo2and Srao2cannot substitute true Svo2values. However, the trend in Scvo2values as well as the trend in Srao2values demonstrated a good correlation with the trend in Svo2values.
The relation between Scvo2and Svo2has been examined in numerous studies with controversial conclusions.6–25 The wide range of conclusions might be the result of different study designs and of different statistical approaches (table 3). Some studies used animal models,12,14,17 whereas other studies examined healthy volunteers21 or patients with myocardial infarction.24 The number of subjects ranged from 79 to 61,7 and the number of comparative pairs of measurements ranged from 276 to 580.9 In most studies, an unequal number of blood samples per subject was drawn,8–14,16,21,25 potentially resulting in an imbalanced statistical weight of subjects with exceedingly good or bad correspondences of Scvo2and Svo2. In addition, in some studies, blood samples were not drawn simultaneously, but sequentially during the advancement of the PA catheter,6–8,16,21 possibly causing arrhythmia31 and thus significantly altering hemodynamic variables, which may result in different oxygen saturations at different sites of measurement.
Table 3. Studies Comparing Mixed Venous Oxygen Saturation and Central Venous Oxygen Saturation 
Image not available
Table 3. Studies Comparing Mixed Venous Oxygen Saturation and Central Venous Oxygen Saturation 
×
Table 3. Continued 
Image not available
Table 3. Continued 
×
Table 3. Continued 
Image not available
Table 3. Continued 
×
Neither a power analysis nor an analysis of method repeatability was presented in previous investigations. A power analysis has to be calculated on the basis of a difference between Svo2and Scvo2that is defined as clinically relevant before the study. Furthermore, this Δ (Svo2− Scvo2) value serves as an a priori  standard, which is necessary to discuss the variability found in the actual study data. Evaluation of the repeatability of single measurements is a very important issue because the repeatability of methods limits the amount of agreement that is possible.27 Therefore, repeatability represents a baseline (within-method variability) to which the between-method variability can be compared.
Most studies present the bias6–8,10,11,13,15–20 as well as correlation coefficients between the measurements.7–20,25 However, calculating bias and correlation coefficients for individual values is not enough for evaluating the agreement of two different methods.26,27 Despite large differences between individual values, the bias (i.e.  , mean of the differences between individual values) might be zero, and the correlation coefficient measures proportionality, not agreement. In 1986, Bland and Altman26 recommended the calculation of 95% limits of agreement of individual values for method comparison studies. However, only 5 of 10 investigations studying the equivalence of Svo2and Scvo2have presented these limits of agreement since then.9–11,14,18 Furthermore, only 8 of 17 studies analyzed the agreement of the trend of oxygen saturations measured at different sites in addition to the agreement of absolute values.8–13,15,17 
The wide range of 95% limits of agreement regarding individual values of Svo2and Scvo2found in our study indicates a large between-method variability. Because the 95% repeatability coefficient was 2.91% in our study, this considerable lack of agreement between the methods is not solely explained by a lack of repeatability. Our finding parallels the results of previous studies, demonstrating an enormous variability of absolute values.6,8–13,16,18 In contrast, some studies found that individual Scvo2values can adequately replace Svo2values,7,15,17,20,24,25 but these studies do not present a statistical analysis that includes more than the evaluation of bias and correlation coefficients. In addition, none of these studies performed a power analysis before the investigation. Therefore, it remains unclear whether a number of 4415,25 or 7620 comparative measurements is enough to detect statistically significant differences. Schou et al.  14 concluded from their data that Svo2and Scvo2are interchangeable, although the 95% limits of agreement plotted in their figures equaled or exceeded ±10%. Because of these controversial results regarding absolute values, there has been a considerable debate on the question of the clinical utility of Scvo2.1,32 
Clinical decisions are rarely based on single measurements but always reflect various variables as well as the trend of these variables. In the early stage of a disease, Scvo2values are often found to be less than 50%, with Svo2values even lower.1 Consequently, these low Scvo2values, although they do not exactly equal Svo2values, may serve as a representative variable guiding therapeutical interventions. Furthermore, not the individual value but the trend of Scvo2may detect an imbalance of oxygen delivery and oxygen consumption. Our study reveals a good correlation between the trends of Svo2and Scvo2, which is in accordance with previous studies.11–13,15 Scheinman et al.  13 found a poor correlation between absolute values in patients with severe heart failure or shock but a better correlation between changes of Svo2and Scvo2. In an animal model, Reinhart et al.  12 demonstrated a close tracking of the oxygen saturations continuously measured in the PA and the SVC across a wide range of hemodynamic conditions. In a recent study, the same group could confirm these findings in critically ill patients.11 Tahvanainen et al.  15 found a significant correlation between PA blood samples and both SVC and RA blood samples during subsequent changes of oxygen saturation in critically ill patients. These data suggest that Scvo2is equivalent to Svo2in the course of clinical decisions as long as absolute values are not required. This is supported by our data, because the degree of correlation between the trend of Scvo2and Svo2is better with larger changes in oxygen saturation. In a recent study, Rivers et al.  33 significantly reduced mortality and organ dysfunction in patients with severe sepsis or septic shock using an early goal-directed therapy approach. The early goal-directed algorithm of the treatment of the first 6 h included the continuous measurement of Scvo2defining an Scvo2value greater than 70% as an endpoint of therapy.33 Although some variables of the algorithm, including Scvo2, have been criticized,34 monitoring Scvo2has recently been declared as appropriate for the management of severe sepsis.5 
In addition, in our study, a comparison between Svo2and Srao2could be performed using the proximal port of the PA catheter for withdrawal of blood samples from the RA. However, 95% limits of agreement were too large to accept individual Srao2values as equivalent to Svo2. The trend of Srao2correlated better with Svo2than those of Scvo2. However, because of potential dangerous complications (e.g.  , arrhythmia, perforation), placing the catheter tip in the RA is not recommended35 or at least debatable.36 
Limitations of the Study
Monitoring Svo2is used as a clinical marker of systemic oxygen utilization in critically ill patients.1 During sepsis, a redistribution of blood flow associated with a proportionally greater reduction in splenic, renal, and mesenteric blood flow may occur,1,32 and in heart failure or circulatory shock, blood flow is relatively increased in cerebral and coronary circulation,8,13 thus altering the relation between Svo2and Scvo2, with Svo2generally lower than Scvo2. However, our study was performed in patients scheduled to undergo elective neurosurgical operations in the sitting position during general anesthesia, resulting in a mean Svo2higher than Scvo2. This study design was chosen because, in our neuroanesthesia department, these patients are routinely monitored with both a PA catheter and a CV catheter (for aspiration of entrained air), whereas critically ill patients are rarely provided with both catheters. Second, this setting, in contrast to the clinical situation of critically ill patients, allows withdrawal of blood samples at different time points that are clearly defined. Third, positioning the patient from the supine position to the sitting position and vice versa  was reported to induce a clear change of hemodynamic variables28,29 due to a change in blood volume distribution from the intrathoracic to the extrathoracic compartment,30 which is demonstrated for the current study. A mean change of 14% in MAP, with ΔMAP greater than 40% in some patients, and a mean difference in CO of 16%, with a maximum ΔCO of 70%, were detected. This might partly mimic the situation of patients in hypovolemic shock and resulted in an increase in bias between Svo2and Scvo2after changing the position from supine to sitting and vice versa  in a decrease in bias after changing the position from sitting to supine. Anesthesia was induced and maintained with intravenous fentanyl and midazolam in all patients. Because both drugs are often used as a sedative or an analgesic on the intensive care unit,37,38 the anesthesia regimen used in our study is not significantly different from sedation regimens used in critically ill patients. Furthermore, fentanyl and midazolam are reported to produce only modest hemodynamic effects.39,40 Therefore, it is unlikely that our findings are significantly affected by the specific anesthesia regimen.
In summary, our study demonstrates that despite some large differences between absolute values, in patients with varying hemodynamic situations, the trend in Scvo2may be used as a surrogate variable for the trend in Svo2.
The authors thank Gernot Wassmer, Ph.D. (Assistant Professor, Institute of Medical Statistics and Epidemiology, University of Cologne, Cologne, Germany), for statistical advice.
References
Rivers EP, Ander DS, Powell D: Central venous oxygen saturation monitoring in the critically ill patient. Curr Opin Crit Care 2001; 7:204–11Rivers, EP Ander, DS Powell, D
Connors Jr, AF Speroff, T, Dawson NV, Thomas C, Harrell Jr, FE Wagner, D, Desbiens N, Goldman L, Wu AW, Califf RM, Fulkerson Jr, WJ Vidaillet, H, Broste S, Bellamy P, Lynn J, Knaus WA: The effectiveness of right heart catheterization in the initial care of critically ill patients. SUPPORT Investigators. JAMA 1996; 276:889–97Connors, AF Speroff, T Dawson, NV Thomas, C Harrell, FE Wagner, D Desbiens, N Goldman, L Wu, AW Califf, RM Fulkerson, WJ Vidaillet, H Broste, S Bellamy, P Lynn, J Knaus, WA
Peters SG, Afessa B, Decker PA, Schroeder DR, Offord KP, Scott JP: Increased risk associated with pulmonary artery catheterization in the medical intensive care unit. J Crit Care 2003; 18:166–71Peters, SG Afessa, B Decker, PA Schroeder, DR Offord, KP Scott, JP
Soni N: Swan song for the Swan-Ganz catheter? BMJ 1996; 313:763–4Soni, N
Dellinger RP, Carlet JM, Masur H, Gerlach H, Calandra T, Cohen J, Gea-Banacloche J, Keh D, Marshall JC, Parker MM, Ramsay G, Zimmerman JL, Vincent JL, Levy MM: Surviving Sepsis Campaign guidelines for management of severe sepsis and septic shock. Crit Care Med 2004; 32:858–73Dellinger, RP Carlet, JM Masur, H Gerlach, H Calandra, T Cohen, J Gea-Banacloche, J Keh, D Marshall, JC Parker, MM Ramsay, G Zimmerman, JL Vincent, JL Levy, MM
Edwards JD, Mayall RM: Importance of the sampling site for measurement of mixed venous oxygen saturation in shock. Crit Care Med 1998; 26:1356–60Edwards, JD Mayall, RM
Ladakis C, Myrianthefs P, Karabinis A, Karatzas G, Dosios T, Fildissis G, Gogas J, Baltopoulos G: Central venous and mixed venous oxygen saturation in critically ill patients. Respiration 2001; 68:279–85Ladakis, C Myrianthefs, P Karabinis, A Karatzas, G Dosios, T Fildissis, G Gogas, J Baltopoulos, G
Lee J, Wright F, Barber R, Stanley L: Central venous oxygen saturation in shock: A study in man. Anesthesiology 1972; 36:472–8Lee, J Wright, F Barber, R Stanley, L
Martin C, Auffray JP, Badetti C, Perrin G, Papazian L, Gouin F: Monitoring of central venous oxygen saturation versus mixed venous oxygen saturation in critically ill patients. Intensive Care Med 1992; 18:101–4Martin, C Auffray, JP Badetti, C Perrin, G Papazian, L Gouin, F
Pieri M, Brandi LS, Bertolini R, Calafa M, Giunta F: Comparison of bench central and mixed pulmonary venous oxygen saturation in critically ill postsurgical patients [in Italian]. Minerva Anestesiol 1995; 61:285–91Pieri, M Brandi, LS Bertolini, R Calafa, M Giunta, F
Reinhart K, Kuhn HJ, Hartog C, Bredle DL: Continuous central venous and pulmonary artery oxygen saturation monitoring in the critically ill. Intensive Care Med 2004; 30:1572–8Reinhart, K Kuhn, HJ Hartog, C Bredle, DL
Reinhart K, Rudolph T, Bredle DL, Hannemann L, Cain SM: Comparison of central-venous to mixed-venous oxygen saturation during changes in oxygen supply/demand. Chest 1989; 95:1216–21Reinhart, K Rudolph, T Bredle, DL Hannemann, L Cain, SM
Scheinman MM, Brown MA, Rapaport E: Critical assessment of use of central venous oxygen saturation as a mirror of mixed venous oxygen in severely ill cardiac patients. Circulation 1969; 40:165–72Scheinman, MM Brown, MA Rapaport, E
Schou H, Perez de Sa V, Larsson A: Central and mixed venous blood oxygen correlate well during acute normovolemic hemodilution in anesthetized pigs. Acta Anaesthesiol Scand 1998; 42:172–7Schou, H Perez de Sa, V Larsson, A
Tahvanainen J, Meretoja O, Nikki P: Can central venous blood replace mixed venous blood samples? Crit Care Med 1982; 10:758–61Tahvanainen, J Meretoja, O Nikki, P
Turnaoglu S, Tugrul M, Camci E, Cakar N, Akinci O, Ergin P: Clinical applicability of the substitution of mixed venous oxygen saturation with central venous oxygen saturation. J Cardiothorac Vasc Anesth 2001; 15:574–9Turnaoglu, S Tugrul, M Camci, E Cakar, N Akinci, O Ergin, P
Davies GG, Mendenhall J, Symreng T: Measurement of right atrial oxygen saturation by fiberoptic oximetry accurately reflects mixed venous oxygen saturation in swine. J Clin Monit 1988; 4:99–102Davies, GG Mendenhall, J Symreng, T
Chawla LS, Zia H, Gutierrez G, Katz NM, Seneff MG, Shah M: Lack of equivalence between central and mixed venous oxygen saturation. Chest 2004; 126:1891–6Chawla, LS Zia, H Gutierrez, G Katz, NM Seneff, MG Shah, M
Herrera A, Pajuelo A, Morano MJ, Ureta MP, Gutierrez-Garcia J, de las Mulas M: Comparison of oxygen saturations in mixed venous and central blood during thoracic anesthesia with selective single-lung ventilation [in Spanish]. Rev Esp Anestesiol Reanim 1993; 40:349–53Herrera, A Pajuelo, A Morano, MJ Ureta, MP Gutierrez-Garcia, J de las Mulas, M
Berridge JC: Influence of cardiac output on the correlation between mixed venous and central venous oxygen saturation. Br J Anaesth 1992; 69:409–10Berridge, JC
Barrat-Boyes BG, Wood EH: The oxygen saturation of blood in the venae cavae, right-heart chambers, and pulmonary vessels of healthy subjects. J Lab Clin Med 1957; 50:93–106Barrat-Boyes, BG Wood, EH
Baquero Cano M, Sanchez Luna M, Elorza Fernandez MD, Valcarcel Lopez M, Perez Rodriguez J, Quero Jimenez J: Oxygen transport and consumption and oxygen saturation in the right atrium in an experimental model of neonatal septic shock [in Spanish]. An Esp Pediatr 1996; 44:149–56Baquero Cano, M Sanchez Luna, M Elorza Fernandez, MD Valcarcel Lopez, M Perez Rodriguez, J Quero Jimenez, J
Faber T: Central venous versus mixed venous oxygen content. Acta Anaesthesiol Scand Suppl 1995; 107:33–6Faber, T
Goldman RH, Klughaupt M, Metcalf T, Spivack AP, Harrison DC: Measurement of central venous oxygen saturation in patients with myocardial infarction. Circulation 1968; 38:941–6Goldman, RH Klughaupt, M Metcalf, T Spivack, AP Harrison, DC
Wendt M, Hachenberg T, Albert A, Janzen R: Mixed venous versus central venous oxygen saturation in intensive medicine [in German]. Anasth Intensivther Notfallmed 1990; 25:102–6Wendt, M Hachenberg, T Albert, A Janzen, R
Bland JM, Altman DG: Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; 1:307–10Bland, JM Altman, DG
Bland JM, Altman DG: Measuring agreement in method comparison studies. Stat Methods Med Res 1999; 8:135–60Bland, JM Altman, DG
Dalrymple DG, MacGowan GF, MacLeod SW: Cardiorespiratory effects of the sitting position in neurosurgery. Br J Anaesth 1979; 51:1079–82Dalrymple, DG MacGowan, GF MacLeod, SW
Porter JM, Pidgeon C, Cunningham AJ: The sitting position in neurosurgery: A critical appraisal. Br J Anaesth 1999; 82:117–28Porter, JM Pidgeon, C Cunningham, AJ
Buhre W, Weyland A, Buhre K, Kazmaier S, Mursch K, Schmidt M, Sydow M, Sonntag H: Effects of the sitting position on the distribution of blood volume in patients undergoing neurosurgical procedures. Br J Anaesth 2000; 84:354–7Buhre, W Weyland, A Buhre, K Kazmaier, S Mursch, K Schmidt, M Sydow, M Sonntag, H
Keusch DJ, Winters S, Thys DM: The patient's position influences the incidence of dysrhythmias during pulmonary artery catheterization. Anesthesiology 1989; 70:582–4Keusch, DJ Winters, S Thys, DM
Vincent JL: Does central venous oxygen saturation accurately reflect mixed venous oxygen saturation? Nothing is simple, unfortunately. Intensive Care Med 1992; 18:386–7Vincent, JL
Rivers E, Nguyen B, Havstad S, Ressler J, Muzzin A, Knoblich B, Peterson E, Tomlanovich M: Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med 2001; 345:1368–77Rivers, E Nguyen, B Havstad, S Ressler, J Muzzin, A Knoblich, B Peterson, E Tomlanovich, M
Marik PE, Varon J: Goal-directed therapy for severe sepsis. N Engl J Med 2002;346:1025–6Marik, PE Varon, J
McGee WT, Ackerman BL, Rouben LR, Prasad VM, Bandi V, Mallory DL: Accurate placement of central venous catheters: A prospective, randomized, multicenter trial. Crit Care Med 1993; 21:1118–23McGee, WT Ackerman, BL Rouben, LR Prasad, VM Bandi, V Mallory, DL
Vesely TM: Central venous catheter tip position: A continuing controversy. J Vasc Interv Radiol 2003; 14:527–34Vesely, TM
Prause A, Wappler F, Scholz J, Bause H, Schulte am Esch J: Respiratory depression under long-term sedation with sufentanil, midazolam and clonidine has no clinical significance. Intensive Care Med 2000; 26:1454–61Prause, A Wappler, F Scholz, J Bause, H Schulte am Esch, J
Soliman HM, Melot C, Vincent JL: Sedative and analgesic practice in the intensive care unit: the results of a European survey. Br J Anaesth 2001; 87:186–92Soliman, HM Melot, C Vincent, JL
Reves JG, Glass PA: Nonbarbiturate intravenous anesthetics, Anesthesia, 5th edition. Edited by Miller RD. Philadelphia, Churchill Livingstone, 2000, pp. 228–72Reves, JG Glass, PA Nonbarbiturate intravenous anesthetics,Miller RD Philadelphia Churchill Livingstone
Bailey PL, Talmage DE, Stanley TH: Intravenous opioid anesthetics, Anesthesia, 5th edition. Edited by Miller RD. Philadelphia, Churchill Livingstone, 2000, pp. 273–376Bailey, PL Talmage, DE Stanley, TH Intravenous opioid anesthetics,Miller RD Philadelphia Churchill Livingstone
Fig. 1. Bland and Altman plot of the differences between replicate mixed venous oxygen saturation (Svo2) measurements against their mean values. Five replicate blood samples were drawn in 17 patients. Each of the resulting five Svo2values per patient were subtracted from each other, resulting in n = 17 · 10 individual differences. The  broken line  indicates the mean difference, and  unbroken lines  indicate repeatability coefficient (mean ± within-subject SD  s  w). 
Fig. 1. Bland and Altman plot of the differences between replicate mixed venous oxygen saturation (Svo2) measurements against their mean values. Five replicate blood samples were drawn in 17 patients. Each of the resulting five Svo2values per patient were subtracted from each other, resulting in n = 17 · 10 individual differences. The  broken line  indicates the mean difference, and  unbroken lines  indicate repeatability coefficient (mean ± within-subject SD  s  w). 
Fig. 1. Bland and Altman plot of the differences between replicate mixed venous oxygen saturation (Svo2) measurements against their mean values. Five replicate blood samples were drawn in 17 patients. Each of the resulting five Svo2values per patient were subtracted from each other, resulting in n = 17 · 10 individual differences. The  broken line  indicates the mean difference, and  unbroken lines  indicate repeatability coefficient (mean ± within-subject SD  s  w). 
×
Fig. 2. Bland and Altman plots of the differences between mixed venous oxygen saturation (Svo2) and central venous oxygen saturation (Scvo2) at different time points. (  T1  ) Supine position after induction of anesthesia and insertion of catheters. (  T2  and  T3  ) During the neurosurgical procedure in the sitting position, with an interval of at least 1 h between. (  T4  ) Supine position after the neurosurgical procedure was completed. The  broken line  indicates the mean difference (bias), and  unbroken lines  indicate 95% limits of agreement (mean ± SD). Note the large 95% limits of agreement. 
Fig. 2. Bland and Altman plots of the differences between mixed venous oxygen saturation (Svo2) and central venous oxygen saturation (Scvo2) at different time points. (  T1  ) Supine position after induction of anesthesia and insertion of catheters. (  T2  and  T3  ) During the neurosurgical procedure in the sitting position, with an interval of at least 1 h between. (  T4  ) Supine position after the neurosurgical procedure was completed. The  broken line  indicates the mean difference (bias), and  unbroken lines  indicate 95% limits of agreement (mean ± SD). Note the large 95% limits of agreement. 
Fig. 2. Bland and Altman plots of the differences between mixed venous oxygen saturation (Svo2) and central venous oxygen saturation (Scvo2) at different time points. (  T1  ) Supine position after induction of anesthesia and insertion of catheters. (  T2  and  T3  ) During the neurosurgical procedure in the sitting position, with an interval of at least 1 h between. (  T4  ) Supine position after the neurosurgical procedure was completed. The  broken line  indicates the mean difference (bias), and  unbroken lines  indicate 95% limits of agreement (mean ± SD). Note the large 95% limits of agreement. 
×
Fig. 3. Changes in mixed venous (ΔSvo2) and central venous oxygen saturation (ΔScvo2) between two measurements. n = 182;  r  = 0.755; equation of the regression line: ΔScvo2= 1.084 ×ΔSvo2+ 0.412. 
Fig. 3. Changes in mixed venous (ΔSvo2) and central venous oxygen saturation (ΔScvo2) between two measurements. n = 182;  r  = 0.755; equation of the regression line: ΔScvo2= 1.084 ×ΔSvo2+ 0.412. 
Fig. 3. Changes in mixed venous (ΔSvo2) and central venous oxygen saturation (ΔScvo2) between two measurements. n = 182;  r  = 0.755; equation of the regression line: ΔScvo2= 1.084 ×ΔSvo2+ 0.412. 
×
Table 1. Mean Differences (Bias) and Correlation Coefficients in Oxygen Saturations of Blood Samples Taken from Various Sites 
Image not available
Table 1. Mean Differences (Bias) and Correlation Coefficients in Oxygen Saturations of Blood Samples Taken from Various Sites 
×
Table 2. Correlation of Changes in Oxygen Saturation of Blood Samples Taken from Different Sites 
Image not available
Table 2. Correlation of Changes in Oxygen Saturation of Blood Samples Taken from Different Sites 
×
Table 3. Studies Comparing Mixed Venous Oxygen Saturation and Central Venous Oxygen Saturation 
Image not available
Table 3. Studies Comparing Mixed Venous Oxygen Saturation and Central Venous Oxygen Saturation 
×
Table 3. Continued 
Image not available
Table 3. Continued 
×
Table 3. Continued 
Image not available
Table 3. Continued 
×