Assessment of macro- and micro-oxygenation parameters during fractional fluid infusion: A pilot study

The main goal of this study was to assess whether maximal fluid infusion improves both oxygen delivery (DO₂) and micro-circulatory parameters during hemodilution. The secondary objective was to assess the ability of baseline micro-circulatory parameters to predict oxygen consumption (VO₂) response following fluid infusion.

In a postoperative cardiac ICU, patients received repeated fluid infusion until stroke volume (SV) was maximized. Before and after each fluid expansion, macro- (DO₂, VO₂) and micro-circulatory oxygenation parameters were recorded [central venous oxygen saturation (ScVO₂), blood lactate, difference in veno-arterial carbon dioxide tension (P(v-a)CO₂), somatic and cerebral oxygen saturation (rSO₂)]. Patients were classified as VO₂-Responders or VO₂-Non-Responders according to an increase in VO₂ above or below 15%, respectively.

After maximal fluid infusion, all patients showed improved macro- and micro-circulatory oxygenation parameters, but VO₂-Responders had lower values (especially for ScVO₂ and cerebral rSO₂). Only baseline ScVO₂ and cerebral rSO₂ were useful to predict the VO₂ response to maximal fluid infusion (ROC_AUC 0.80 (95% CI: 0.54-0.95, P=0.012) and 0.83 (95% CI: 0.57-0.96, P=0.001).

Maximal fluid infusion improves macro- and micro-circulatory oxygenation parameters. For VO₂-Responders, only ScVO₂ and cerebral rSO₂ could serve as markers of tissue hypoxia.