Background

How phenylephrine and ephedrine treatments affect global and regional haemodynamics is of major clinical relevance. Cerebral tissue oxygen saturation ()-guided management may improve postoperative outcome. The physiological variables responsible for changes induced by phenylephrine and ephedrine bolus treatment in anaesthetized patients need to be defined.

Methods

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. , 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.

Results

The CO decreased significantly after phenylephrine treatment [▵CO=−2.1 (1.4) litre min−1, P<0.001], but was preserved after ephedrine treatment [▵CO=0.5 (1.4) litre min−1, P>0.05]. The was significantly decreased after phenylephrine treatment [▵=−3.2 (3.0)%, P<0.01] but preserved after ephedrine treatment [▵=0.04 (1.9)%, P>0.05]. CO was identified to have the most significant association with (P<0.001). After taking CO into consideration, the other physiological variables, including MAP, were not significantly associated with (P>0.05).

Conclusions

Associated with changes in CO, decreased after phenylephrine treatment, but remained unchanged after ephedrine treatment. The significant correlation between CO and implies a cause–effect relationship between global and regional haemodynamics.

The relative roles of phospholipid fatty acyl chain length and phospholipid fatty acyl chain unsaturation in the determination of rat renal brush border membrane order were examined using multilamellar liposomes. Exposure of brush border membranes to sphingomyelinase resulted in a time- and concentration-dependent decrement in sphingomyelin content. Liposomes prepared from lipid extracts of these membranes were reconstituted to defined phosphatidylcholine (PC)/sphingomyelin (SPH) ratios with pure synthetic PCs of defined chain length and degrees of unsaturation. Mixed-acid PCs from bovine liver, egg, and the rat renal brush border membrane were also examined. The steady state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) at 37 degrees C was used to reflect acyl chain packing. The steady state anisotropy of DPH in liposomes isolated from the rat renal brush border membrane averaged 0.205 +/- 0.001, n = 8. When liposomes were reconstituted to PC/SPH ratios of 1.1, 1.6, and 2.4 with saturated PCs of acyl chain length 16 to 22, differences in anisotropy between groups were not observed. However, when PCs containing unsaturated or mixed-acid fatty acyl chains were introduced, anisotropy decreased in a concentration dependent fashion. These data suggest that phospholipid fatty acyl chain unsaturation, but not acyl chain length, has a powerful influence on renal brush border membrane order and the PC/SPH ratio is an important determinant of renal membrane order by virtue of the unsaturated fatty acids normally present with these phospholipids.