The Catecholamines Plasma blood test is used to measure the amount of the hormones epinephrine, norepinephrine and dopamine in the blood. These are hormones which are made by nerve tissue, the brain and the adrenal glands. Catecholamines held the body respond to stress or fear and prepare the body for its fight or flight reactions. Catecholamines increase heart rate, blood pressure, breathing rate, muscle strength and mental alertness. By doing this, they lower the amount of blood going to the skin and intestines and increase blood to vital organs like the brain, heart and kidneys.