Can central venous oxygen saturation intermittently measured within the first 24 postoperative hours of cardiac surgery predict death?

Background

Central venous oxygen saturation (ScVO₂) has been considered an important parameter for follow-up, prognostic estimate, and therapeutic target in the management of critically ill patients.

Objective

To analyze the impact of ScVO₂ on the postoperative period of cardiac surgery, and to correlate it with inhospital death. Three ScVO₂ measurements were taken within the first 24 postoperative hours, and the overall mean was calculated.

Case series and methods

A classic cohort of 132 consecutive patients selected from January 2004 to August 2004 and divided into the following two groups: Group I, death (n = 11, 8.3%); and Group II, survivors. Blood samples were collected through a central venous catheter properly positioned in the right atrium according to a previously validated method. The ScVO₂ measurements were taken in the postoperative period as follows: immediately (SV0), after 6 hours (SV1), and after 24 hours (SV2). A mean of the three measurements was calculated (mSV). Inhospital mortality was the occurrence of death during hospitalization. The Student t test was used for statistical analysis.

Results

The mean ScVO₂ values of Group I compared with those of Group II were as follows, respectively: SV0, 54.8% ± 12.6 vs 65.4% ± 8.9 (P < 0.0001); SV1, 56.6% ± 7.3 vs 68.5% ± 5.9 (P < 0.001); SV2, 61.1% ± 7 vs 69.3% ± 5.3 (P < 0.001); and mSV, 57.3% ± 7.8 vs 67.7% ± 4.9 (P < 0.001). The distribution of variation of ScVO₂ was normal. The EuroScore was as follows: in the total sample, 5.3 ± 3.6; in Group I, 8.7 ± 6.1; and in Group II, 5 ± 3.1 (P = 0.001). The predicted mortality was around 11%, and the inhospital mortality was 8.3%.

Conclusions

In the population studied, a lowest ScVO₂ measured within the first 24 postoperative hours and the EuroScore were related to inhospital death.

Figure 1