Effect of phenylephrine and ephedrine bolus treatment on cerebral oxygenation in anaesthetized patients

How phenylephrine and ephedrine treatments affect global and regional haemodynamics is of major clinical relevance. Cerebral tissue oxygen saturation (SctO2)-guided management may improve postoperative outcome. The physiological variables responsible for SctO2 changes induced by phenylephrine and ephedrine bolus treatment in anaesthetized patients need to be defined. A randomized two-treatment cross-over trial was conducted: one bolus dose of phenylephrine (100–200 µg) and one bolus dose of ephedrine (5–20 mg) were given to 29 ASA I–III patients anaesthetized with propofol and remifentanil. SctO2, mean arterial pressure (MAP), cardiac output (CO), and other physiological variables were recorded before and after treatments. The associations of changes were analysed using linear-mixed models. The CO decreased significantly after phenylephrine treatment [▵CO=−2.1 (1.4) litre min−1, P0.05]. The SctO2 was significantly decreased after phenylephrine treatment [▵SctO2=−3.2 (3.0)%, P0.05]. CO was identified to have the most significant association with SctO2 (P0.05). Associated with changes in CO, SctO2 decreased after phenylephrine treatment, but remained unchanged after ephedrine treatment. The significant correlation between CO and SctO2 implies a cause–effect relationship between global and regional haemodynamics.