Mechanisms of Vasovagal Syncope

"Phenylephrine dose-response comprises infusion of 0.5, 1, 2, 3, 4 micrograms/kg/min for 10 min at each dose.~If bloods pressure increases by 30% or if heart rate decreases below 40 beats per minute we will stop infusion."

Systemic L-NMMA is infused as a 500μg/kg/min loading dose for 15 min followed by a 50μg/kg/min maintenance dose for the remainder of the experiment.