Hopefully the Neo dose was 400 mcg/min, not mcg/kg/min.
I am not sure about the answer to your question. Neo is a pure alpha agonist. Throwing dopamine into the mix would give you some beta stimulation at low doses (possibly boosting your pt's heart rate), and alpha only at high doses.
Consulting Dr. Google gives a couple interesting hits:
That link says: "Norepinephrine appears to be more predictable and efficient at augmenting CPP when compared with dopamine."
Another link is:
Comparison of Dopamine and Norepinephrine after Traumatic Brain Injury and Hypoxic-Hypotensive Insult | Abstract
That abstract references a study in which norepinephrine and dopamine were compared for efficacy in boosting CPP following a hypoxic brain insult. A couple interesting statements from the abstract shown above:
"After severe brain trauma, blood-brain barrier disruption and alteration of cerebral arteriolar vasoreactive properties may modify the cerebral response to catecholamines."
"Both norepinephrine and dopamine failed to increase CPP, and ICP was significantly higher in TNE and TDA groups than in T group. Interestingly, norepinephrine was not able to alleviate the decrease in MAP. Neither norepinephrine or dopamine could induce an increase of MAP. LCBF decreased similarly in T, TNE and TDA groups. In conclusion, norepinephrine and dopamine are not able to restore values of CPP above 70 mm Hg in a model of severe brain trauma. Furthermore, their systemic vasopressor properties are altered."
It's interesting to me that following brain injury, pressors may no longer work the way we expect them to. In the past, I've seen vasopressin used in head trauma pts suffering from hypotension refractory to catecholamines. Different receptors, and all that jazz.
An interesting mention of vasopressin use in that situation is:
Vasopressin in Acute Brain Injury: A Note of Caution