Cerebral oxygenation and haemodynamic effects induced by nimodipine in healthy subjects

Cerebrovascular effects of nimodipine are still poorly understood even in the healthy condition, in particular effects on tissue oxygenation have never been investigated. The present study aims at investigating changes in cerebral oxygenation and blood volume upon oral administration of nimodipine (90 mg) in the healthy condition. In 8 subjects, changes in cerebral tissue oxygenation and blood volume were determined simultaneously to changes in blood velocity of middle cerebral artery (VMCA) by using, respectively, near infrared spectroscopy (NIRS) and transcranial Doppler ultrasonography (TCD). The subjects also underwent non-invasive assessment of arterial blood pressure (ABP) and end-tidal CO2. TCD and NIRS CO2 reactivity indices were also extracted. Nimodipine, significantly reduced ABP (11  13 %) and increased heart rate, as well as NIRS oxygenation (6.0  4.8 %) and blood volume indices (9.4  10.1 %), while VMCA was not significantly decreased (2.0  3.5 %). Nimodipine slightly but significantly reduced the VMCA response to changes in pCO2 whereas the CO2 reactivity of NIRS parameters was improved. The observed changes in cerebral tissue oxygenation and blood volume indicate a nimodipine-induced cerebrovascular dilatation and increased perfusion, while the effect on VMCA possibly results from a dilatation of the insonated artery. The present results raise doubts about the putative nimodipine-induced impairment of CO2 reactivity.