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

Abstract Purpose The main goal of this study was to assess whether maximal fluid infusion improves both oxygen delivery (DO 2 ) and micro-circulatory parameters during hemodilution. The secondary objective was to assess the ability of baseline micro-circulatory parameters to predict oxygen consumption (VO 2 ) response following fluid infusion. Materials and methods In a postoperative cardiac ICU, patients received repeated fluid infusion until stroke volume (SV) was maximized. Before and after each fluid expansion, macro- (DO 2 , VO 2 ) and micro-circulatory oxygenation parameters were recorded [central venous oxygen saturation (ScVO 2 ), blood lactate, difference in veno-arterial carbon dioxide tension (P(v-a)CO 2 ), somatic and cerebral oxygen saturation (rSO 2 )]. Patients were classified as VO 2 -Responders or VO 2 -Non-Responders according to an increase in VO 2 above or below 15%, respectively. Results After maximal fluid infusion, all patients showed improved macro- and micro-circulatory oxygenation parameters, but VO 2 -Responders had lower values (especially for ScVO 2 and cerebral rSO 2 ). Only baseline ScVO 2 and cerebral rSO 2 were useful to predict the VO 2 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). Conclusions Maximal fluid infusion improves macro- and micro-circulatory oxygenation parameters. For VO 2 -Responders, only ScVO 2 and cerebral rSO 2 could serve as markers of tissue hypoxia.