Effect of reduced cerebral perfusion pressure on cerebral blood flow following inhibition of nitric oxide synthesis.
OBJECTIVE
The authors tested the hypothesis in a porcine model that inhibition of nitric oxide synthesis during reduced cerebral perfusion pressure (CPP) affected the relative cerebral blood flow (CBF) and the cerebrovascular resistance.


METHODS
The CPP was reduced by inducing high cerebrospinal fluid pressure and hemorrhagic hypotension. With continuous blood and intracranial pressure monitoring, relative CPP was estimated using the laser Doppler flowmetry technique in nine pigs that received 40 mg/kg nitro-L-arginine methyl ester (L-NAME) and in nine control animals. The L-NAME caused a decrease in relative CBF (p < 0.01) and increases in cerebrovascular resistance (p < 0.01), blood pressure (p < 0.05), and CPP (p < 0.001). During high intracranial pressure there were no significant differences between the treated animals and the controls. After hemorrhage, there was no significant difference between the groups initially, but 30 minutes later the cerebrovascular resistance was decreased in the control group and increased in the L-NAME group relative to baseline (p < 0.05). Combined hemorrhage and high intracranial pressure increased the difference between the two groups with regard to cerebrovascular resistance (p < 0.05).


CONCLUSIONS
These results suggest that nitric oxide synthesis inhibition affects the autoregulatory response of the cerebral circulation after cardiovascular compensation has taken place. Nitric oxide synthesis inhibition enhanced the undesirable effects of high intracranial pressure during hypovolemia.
Rise
I R
IR
Institute for Surgical Research, The National Hospital, Oslo, Norway.
Kirkeby
O J
OJ
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D001810:Blood Volume / Q000502:physiology; D002543:Cerebral Hemorrhage / Q000503:physiopathology; D015170:Cerebrospinal Fluid Pressure / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006487:Hemostasis / Q000502:physiology; D019586:Intracranial Hypertension / Q000503:physiopathology; D019585:Intracranial Hypotension / Q000503:physiopathology; D007427:Intracranial Pressure / Q000502:physiology; D017078:Laser-Doppler Flowmetry; D008297:Male; D008991:Monitoring, Physiologic; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D013552:Swine; D013997:Time Factors; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester