Comparison of dopamine and norepinephrine after traumatic brain injury andhypoxic-hypotensive insult

After severe brain trauma, blood-brain barrier disruption and alteration of cerebral arteriolar vasoreactive properties may modify the cerebral respon se to catecholamines. Therefore, the goal of the present study was to compa re the effects of dopamine and norepinephrine in a model of brain injury th at consisted of a weight-drop model of injury complicated by a 15-min hypox ic-hypotensive insult (HH). Sprague-Dawley rats (n = 7 in each group) recei ved, after brain injury, an infusion of either norepinephrine (TNE group) o r dopamine (TDA group) in order to increase cerebral perfusion pressure (CP P) above 70 mm Hg. In addition, a control group (C group, no trauma) and a trauma group (T group, brain injury, no catecholamine infusion) were studie d. Mean arterial pressure (MAP), intracranial pressure (ICP, intraparenchym al fiberoptic device), and local cerebral blood flow (LCBF, extradural lase r-Doppler fiber) were measured throughout the protocol. In T group, brain i njury and RH induced a decrease in CPP (by an increase of ICP and a decreas e of MAP), and a decrease of LCBF. Both norepinephrine and dopamine failed to increase CPP, and ICP was significantly higher in TNE and TDA groups tha n in T group. Interestingly, norepinephrine was not able to alleviate the d ecrease 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 vasopr essor properties are altered.