Purpose: To determine the appropriate concentration of papaverine for therapeutic intraarterial infusion against cerebral vasospasm.
Methods: We investigated histopathologic changes in cerebral arteries and brain tissue of normal Wistar rats that had received infusions of papaverine via the carotid artery. Rats were infused with 0.20 mL papaverine (concentration, 0.4% to 4.0%) via the internal carotid artery. Injury to the vascular wall was evaluated by transmission electron microscopy; pathologic changes in cerebral tissue were studied by light microscopy.
Results: Neither brain necrosis nor brain edema was seen under light microscopy at any concentration. At 4.0% papaverine concentration, degeneration of endothelial cells and medial smooth muscle, including vacuole formation, was observed under electron microscopy. At 1.4% concentration, degeneration of endothelial cells was seen. Extravasation of Evans blue dye was noted when drug concentration exceeded 1.4%. At 0.8% concentration, no histopathologic change was noted.
Conclusion: On the basis of these results, we recommend a papaverine concentration of 0.8% or less for intraarterial infusion.