Phenylephrine versus Norepinephrine in Septic Shock
Phenylephrine, a pure α-agonist with vasoconstrictive effects similar to norepinephrine, but without chronotropic or inotropic effects. This leads to increased afterload, reflex bradycardia, and possibly a drop in the cardiac output.
A small study of 32 patients showed that there is no differences in terms of cardiopulmonary performance, global oxygen transport, and regional hemodynamics when compared with norepinephrine. However, it is not recommended as an initial vasopressor due to its potential association with reduced splanchnic blood flow in septic shock patients. \
During the shortage of norepinephrine in the US in 2011, a cohort study of 27,835 patients revealed an association between the norepinephrine shortage and mortality among adults with septic shock, during this period, the most commonly administered alternative vasopressor was phenylephrine.
Therefore, we discourage the use of phenylephrine in general. If used, we recommend to limit it to patients who:
develop tachyarrhythmias on norepinephrine, epinephrine, or dopamine.
have persistent shock despite use of two or more vasopressor/inotropic agents including vasopressin (salvage therapy).
or have high cardiac output with persistent hypotension.
Vail E, Gershengorn HB, Hua M, Walkey AJ, Rubenfeld G, Wunsch H. Association Between US Norepinephrine Shortage and Mortality Among Patients With Septic Shock. JAMA. 2017;317(14):1433–1442.
