Why it works?

ICU: shock => whole-body vasodilation => need vasopressors => NorEpi is the to-go since it does not usually cause arrhythmia as Dopamine does.  NorEpi with its ability to do more alpha 1 and alpha 2 is preferred because it doesn't really act on beta 1 that much which may cause arrhythmia. Dopamine also have beta 1 effects therefore it causes increased heart rate in the already very sick and weak heart, therefore it's not as preferred. However, Dopamine is usually recommended due to the belief that with its Dopaminergic receptors, it will have more renal perfusion during shock. Phenylephrine being too strong alpha vasoconstrictors causing gangrene, so it's not the first line drug.

~Wonder Me!