Is venous oxygen saturation a predictor of optimal oxygen delivery in adult patients undergoing cardiac surgery with the use of extracorporeal circulation and mild hypothermia at 34°c?

Abstract

INTRODUCTION
Specifically, venous oxygen saturation during extracorporeal circulation indicates the relationship between the supply and consumption of oxygen in the body. Normal values are between 70% and 80%, until now it is an indicator of adequate tissue perfusion during extracorporeal circulation. But even in situations where venous oxygen saturation is within normal limits, this value could be masking silent or hidden hypoperfusion, so we would be facing an increase in serum lactate concentration and little oxygen delivery to all organs.

OBJECTIVE
To determine whether venous oxygen saturation is a predictor of optimal oxygen delivery in adult patients undergoing cardiac surgery using extracorporeal circulation and mild hypothermia at 34°C.

METHOD
The study included all adult patients who met the inclusion criteria in the period from January to May 2021. Blood sampling, for arterial and venous blood gases, which were taken simultaneously at the time of reaching the temperature at 34°C, once these two results were obtained, they were compared and the arterial oxygen saturation, venous oxygen saturation, both arterial and venous oxygen pressure were measured, these results were entered in the application of the Latin American Association of perfusion and we also verified them with the Fick formula.

RESULTS
The data was analyzed with the statistical software IBM SPSS version 2.5, the Shapiro-Wilk test was used to demonstrate the normality of the variables, the Pearson correlation test to relate the variables and the student's t-test to assess statistical significance.

CONCLUSIONS
Venous oxygen saturation can be considered a good predictor of adequate oxygen delivery in adult patients as long as this value is around 80% and perfusion is performed at cardiac indices greater than or equal to 2.32 L/min/m2 in patients. the entire extracorporeal circulation line at 34°C. Reducing flow or cardiac indices below 2.32 L/min/m2 does not guarantee optimal oxygen delivery and reduces venous oxygen saturation despite temperature reduction to 34°C. Adult patients with a temperature of 34°C should be perfused with flows used in normothermia.