• Rajat Dhar, Chad Washington, Michael Diringer, Allyson Zazulia, Hussain Jafri, Colin Derdeyn, and Gregory Zipfel.
• Division of Neurocritical Care, Department of Neurology, Washington University in St. Louis, 660 S Euclid Avenue, St. Louis, MO, 63110, USA. dharr@neuro.wustl.edu.
• Neurocrit Care. 2016 Oct 1; 25 (2): 201-4.

BackgroundThe phosphodiesterase-5 inhibitor sildenafil has been shown to attenuate delayed cerebral ischemia (DCI) and improve neurologic function in experimental subarachnoid hemorrhage (SAH). We recently demonstrated that it could improve cerebral vasospasm (CVS) in humans after SAH. However, successful therapies for DCI must also restore cerebral blood flow (CBF) and/or autoregulatory capacity. In this study, we tested the effects of sildenafil on CBF in SAH patients at-risk for DCI.MethodsSix subjects with angiographically confirmed CVS received 30-mg of intravenous sildenafil (mean 9 ± 2 days after aneurysmal SAH). Each underwent (15)O-PET imaging to measure global and regional CBF at baseline and post-sildenafil.ResultsMean arterial pressure declined by 10 mm Hg on average post-sildenafil (8 %, p = 0.01), while ICP was unchanged. There was no change in global CBF (mean 34.5 ± 7 ml/100g/min at baseline vs. 33.9 ± 8.0 ml/100g/min post-sildenafil, p = 0.84). The proportion of brain regions with low CBF (<25 ml/100g/min) was also unchanged after sildenafil infusion.ConclusionsInfusion of sildenafil does not lead to a change in global or regional perfusion despite a significant reduction in cerebral perfusion pressure. While this could reflect the ineffectiveness of sildenafil-induced proximal vasodilatation to alter brain perfusion, it also suggests that cerebral autoregulatory function was preserved in this group. Future studies should assess whether sildenafil can restore or enhance autoregulation after SAH.

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