Effect of intra-arterial sodium nitroprusside on intracranial pressure and cerebral autoregulation

In cats with normal intracerebral pressure (ICP), administration of sodium nitroprusside (40 micrograms/Kg/min) through the common carotid leads to an increase of ICP, which is attributed to vasodilatation. When ICP is raised gradually to 40 mmHg by intracisternal infusion of artificial CSF prior to the application of SNP, increments of ICP due to SNP become smaller. This reduced vasodilatatory response can be attributed to either a decrease in cerebral perfusion pressure or a direct influence of intra-arterially administered SNP on the autoregulatory capacity of cerebral vessels.