Cerebral oxygenation and haemodynamic effects induced by nimodipine in healthy subjects

The cerebrovascular effects of nimodipine are still poorly understood even in the healthy condition; in particular, its effects on tissue oxygenation have never been investigated. The aim of the present study was to investigate changes in cerebral oxygenation and blood volume upon oral administration of nimodipine (90 mg) in the healthy condition. In eight subjects, changes in cerebral tissue oxygenation and blood volume were determined simultaneously with changes in blood velocity of the middle cerebral artery (V_MCA) 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 endtidal 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 V_MCA was not significantly decreased (2.0±3.5%). Nimodipine slightly but significantly reduced the V_MCA 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 nimodipine-induced cerebrovascular dilation and increased perfusion, while the effect on V_MCA possibly results from dilation of the insonated artery. The present results cast doubt on the putative nimodipine-induced impairment of CO₂ reactivity.