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Cardiac index estimation using central venous oxygen saturation (Scv O2) in critical illness

Background

The use of PA catheter is associated with increased costs and risks to the patients. Central venous (superior vena cava) oxygen saturation obtained by a less risky and costly manner can be used to estimate Sv O2 with great accuracy up to 92% according to our results.

Objective

The aim of this study was to find whether estimated values of Sv O2 can estimate with accuracy cardiac index using Fick method in comparison with thermodilution in critically ill patients.

Material and methods

Sixty-one critically ill patients were catheterized (Opticath PA Catheter P7110 Abbot) upon their admission and the values of Sv O2, Scv O2 and CI were simultaneously measured.

Results

The value of Sv O2 was 68.6% ± 1.1 (X ± SEM), the value of Scv O2 was 69.4% ± 1.1, pearson correlation coefficient was r = 0.95 and r 2 = 0.89 with standard error 3.01. The power model of regression analysis which has the expression Sv O2 = b0 (Scv O2)b1 [in our patients Sv O2 = 1.1612 (Scv O2)0.9617] was found to better describe the relation between the two variables with value of r 2 = 0.92. That means we can estimate the value of Sv O2 from the value of Scv O2 with accuracy 92%. We used estimated values of Sv O2 with power model in Fick equation to estimate CI values and we correlated the estimated CI values with thermodilution CI values. Thermodilution CI values were 3.93 ± 0.17 (range = 1.85-9.3) and Fick method CI values were 3.88 ± 0.18 (range = 1.3-9.76). Pearson correlation coefficient between them was r = 0.86 and r 2 = 0.73 with high significance (P < 0.001).

Discussion-conclusion

Scv O2 can be used as a mirror of Sv O2 for the initial evaluation of critically ill patients with value of r = 0.95 and r 2 = 0.89. These results are in accordance with other authors [1,2]. However, some others found that there is poor correlation and questioned the usefulness of Scv O2 measurement [3]. Power model of regression analysis which has the expression Sv O2 = 1.1612 (Scv O2)0.9617 can estimate the value of Sv O2 from the value of Scv O2 with accuracy 92% (r 2 = 0.92). The use of estimated (with power model) value of Sv O2 in Fick equation can estimate the value of CI with accuracy 86% in comparison with thermodilution (value of r = 0.86).

References

  1. 1.

    Goldman RH, Braniff B, Harrison DC, Spivac AP: The use of central venous oxygen saturation measurement in a coronary care unit. Ann Intern Med 1968, 68: 1280.

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Ladakis, C., Myrianthefs, P., Lappas, V. et al. Cardiac index estimation using central venous oxygen saturation (Scv O2) in critical illness. Crit Care 3, P144 (2000). https://doi.org/10.1186/cc518

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Keywords

  • Catheter
  • Regression Analysis
  • Emergency Medicine
  • Initial Evaluation
  • Oxygen Saturation