Perivascular action of the local anaesthetic, lidocaine, on pial terminal arterioles: direct observations on the microcirculation.

Considerable controversy currently exists with respect to whether or not local anaesthetics exert direct action on cerebral arteriolar tone. In situ experiments were therefore undertaken on pial terminal arterioles of rats to determine whether or not perivascular application of lidocaine exerts any action on such cerebral vessels. Vessel size was assessed with an image-splitting television microscope recording system. The vessels studied ranged in size from 25 to 30 micron. Lidocaine was applied in artificial CSF in dosages of 0.01, 0.1, 1.0 and 2.0 mg. Significant dose-dependent dilatation (i.e., 15.7-45.3% increases in lumen sizes) of the pial terminal arterioles was observed. The results are discussed in light of current developments concerning the mechanism whereby local anaesthetics alleviate increased intracranial pressure and cerebral vasospasm.