What factors can affect cardiac output?

Cardiac output. In strict physiologic terms, cardiac output is determined by something called stroke volume and heart rate. Heart rate is self-explanatory. Stroke volume is the amount of blood that the heart pumps out with each beat. This in turn is dependent on blood pressure, total blood volume, and how strong the heart contracts.
So many things. Drugs, volume of fluid in your body, infection, other illnesses, etc. The list is extremely long.