Why is there a reduced cardiac output in diabetic ketoacidosis?

Hypovolemia: The reduced cardiac output is largely due to the dehydration and volume loss from the polyuria (increased urination), and often times nausea/vomiting. Cardiac output is determined by heart rate times stroke volume. The heart can only compensate so much by increasing the rate when you don't have the blood volume to pump. Eventually, a decreasing ph also prevents the heart from contracting as well.