[Influence of perfusion status on central and mixed venous oxygen saturation in septic patients]

Although there is controversy regarding the role of venous oxygen saturation in the initial resuscitation of septic patients with hypoperfusion, these markers are still widely used. This study aimed to evaluate the correlation and concordance between central (SvcO₂) and mixed (SvO₂) oxygen saturation in septic shock patients with or without hypoperfusion, in addition to the impact of these differences in patient conduction.

Patients with septic shock were monitored with pulmonary artery catheter and the following subgroups of hypoperfusion were analyzed: 1) lactate>28mg.dL^-1; 2) base excess ≤ -5mmoL.L^-1; 3) venoarterial CO₂ gradient>6mmHg; 4) SvO₂<65%; 5) SvcO₂<70%; 6) lactate>28mg.dL^-1 and SvO₂<70%; 7) lactate>28mg.dL^-1 and SvcO₂<75%.

Seventy-seven samples from 24 patients were included. There was only a moderate correlation between SvO₂ and SvcO₂ (r=0.72, p=0.0001) and there was no good concordance between these variables (7.35% bias and 95% concordance limits of -3.0%-17.7%). Subgroup analysis according to the presence of hypoperfusion showed no differences in concordance between variables. There was discordance regarding clinical management in 13.8% (n=9) of the cases.

There is a moderate correlation between SvO₂ and SvcO₂; however, the concordance between them is inadequate. It was not possible to demonstrate that the presence of hypoperfusion alters the concordance between SvO₂ and SvcO₂. The use of SvO₂ instead of SvcO₂ may lead to changes in clinical management in a small but clinically relevant portion of patients.