Epinephrine will increase central pressure via alpha agonist effects. The dose, timing and indications for epinephrine use are based on animal studies.
Recent studies question whether epinephrine provides any overall benefit for human patients.
Studies do show that epinephrine for out-of-hospital cardiac arrest will increase the rate of pulse return. The problem is that it doesn't considerably alter longer-term survival. A large Japanese study showed that, despite an increase in pulse return, epinephrine reduces long-term survival (to hospital discharge) and patients who do survive have significantly worse neurological outcomes than patients who did not receive the drug. Perhaps harmful epinephrine-induced reductions in micro-vascular blood flow offset the useful effects of the increase in central circulation.
In a V-Fib or pulseless ventricular tachycardia code situation, epinephrine should NOT be administered until after the second shock (per guidelines) for precisely these reasons. The patient's best chance of a neurologically intact survival is immediate CPR, a shock as soon as available, and two more minutes of uninterrupted CPR. A second shock (followed by epinephrine administration) is only indicated if there is no return of ROSC by that time.
Guidelines do say that it is reasonable to administer epinephrine as soon as practical in an asystole or PEA code, as no shock is advised.
Hagihara A., Hasegawa M., Abe T., Nagata T., Wakata Y., Miyazaki S.; Prehospital epinephrine use and survival among patients with out-of-hospital cardiac arrest. JAMA. 2012;307:1161-1168.
Dumas F, Bougouin W, Geri G, et al. Is Epinephrine During Cardiac Arrest Associated With Worse Outcomes in Resuscitated Patients?. J Am Coll Cardiol. 2014;64(22):2360-2367. doi:10.1016/j.jacc.2014.09.036.