Question

A patient is given a large intravenous injection of norepinephrine that causes artery constriction, vein constriction, and direct actions on the heart. Describe how this would affect heart afterload, preload, and contractility. Given all of these effects, do you expect that cardiac output will increase, decrease, or not change? Be sure to explain your answer.

Answer 1

Norepinephrine is a vasopressor and is used to correct hypotension and is used in patients with cardiogenic shock.It basically stimulates alpha receptors to cause peripheral constriction and increase blood pressure.It has positive ionotropic effect on the heart at higher doses and this causes increased systemic vascular resistance and mean arterial pressure which causes increased preload and contractility and subsequent increase in afterload.

The cardiac output remains more or less stable for low doses and then begins to drop towards high range of doses this is because of combination of increased afterload and myocardial damage due to some shock(septic cardiogenic shock)