Blood pressure effects of ephedrine treatment.

“Pre-injection” were averaged data −5 to 0 minutes pre injection, “post injection” was averaged −5 to 0 minutes before onset of hypoxia, and “hypoxia” was averaged 30–40 minutes post injection. A, B: Treatment with high dose ephedrine (20 mg/kg), alone and combination with ambrisentan, significantly increased MAP and PAP, under normoxia and hypoxia, compared to baseline (repeated measures ANOVA with Bonferroni correction, p<0.05), and compared to the other treatment groups (one-way ANOVA/Bonferroni, p<0.001). Onset of hypoxia significantly decreased MAP in these groups (repeated measures ANOVA with Bonferroni correction, p<0.05). In the control group, PAP increased significantly after onset of hypoxia (N = 7–14). C: Experimental schedule to measure the influence of treatment on oxygen concentration in the hind muscle. Tissue hypoxia was measured by pO₂ needle electrode tracings during inspired normoxia (1) and hypoxia at baseline (2), before (3) and after injection under normoxia (4), and during post-injection hypoxia (5). D: under post-treatment normoxia (panel D time point #4), ephedrine alone and in combination with ambrisentan significantly increased muscle oxygenation, compared to pre-treatment pO₂ (one-way ANOVA with Bonferroni correction, N = 4–8, p<0.05). E: Under post-treatment hypoxia (panel D #5), only the combination of high ephedrine and ambrisentan significantly increased muscle oxygen tension. Re-oxygenation after combo treatment was significantly higher than in all other treatment groups (one-way ANOVA/Bonferroni, N = 4–8, p<0.05 * or 0.01**). F: Low dose ephedrine (2 mg/kg) significantly increases blood flow in the hind leg muscle when combined with ambrisentan, but not alone.