Correlation of mixed venous and central venous oxygen saturation and its relation to cardiac index

• Published in: Indian journal of critical care medicine Vol. 10; no. 4
• Main Author: Ramakrishna MN, Hegde DeviPrasad, Kumaraswamy GN, Gupta Ratan, Girish TN
• Format: Journal Article
• Language: English
• Published: Medknow Publications on behalf of the Indian Society of Critical Care Medicine 04-02-2007
• Subjects: Cardiac index, central venous oxygen saturation, mixed venous oxygen saturation, shock
• ISSN: 0972-5229

Background and Aim: The clinical applicability of substitution of
central venous oxygen saturation for mixed venous oxygen saturations in
monitoring global tissue hypoxia is still a matter of controversy.
Hence aim of the study is comparison of paired samples of mixed venous
and central venous oxygen saturation and comparison in relation to
cardiac index in varying hemodynamic conditions. Materials and
Methods: Prospective clinical observation: Postoperative cardiac
surgical ITU: 60 adult patients,> 18 years of age of either sex: A
PAC was inserted through ® IJV, triple lumen catheter was inserted
through ® IJV. Blood samples were taken from distal tip of PAC and
central venous catheters. An arterial blood sample was drawn from
either radial or femoral arterial line. Measurements: Continuous
cardiac output monitoring. Analysis of blood samples for hemoglobin
concentration and oxygen saturation. Mixed venous oxygen saturations
and central venous oxygen saturations were compared. The study was
carried over a period of 30h in the postoperative period and samples
were taken at 6h intervals. Patients were classified into three groups
as follows depending on the CI: Low (< 2.5 L/m 2), medium (2.5-4 L/m
2), high (> 4 L/m2) and correlated with Svo 2 and Scvo 2 . Results:
298 Comparative sets of samples were obtained. Svo2 was consistently
lower than Scvo2 throughout the study period. The difference was
statistically significant. By using Bland - Altman plot, the mean
difference between Svo 2 and Scvo 2 (Svo 2 -Scvo 2 ) was - 2.9% ±
5.14 and confidence limits are + 7.17% and - 12.97%. The co-efficient r
is > 0.7 throughout the study period for all paired samples. The
correlation Svo 2 and Scvo 2 with cardiac index in all the three groups
were > 0.7. Conclusion: Scvo 2 and Svo 2 are closely related and
are interchangeable. Even though individual values differ trends in
Scvo 2 may be substituted for trend in Svo 2