Fig. 2. Changes during the first few minutes after cessation of propofol infusion and simultaneous commencement of sevoflurane administration in an individual patient (No. 18) during carotid endarterectomy. Changing from propofol to sevoflurane was associated with a decrease in internal carotid artery pressure (ICAP) so that the gradient between ICAP and mean arterial pressure (MAP) widened. In this patient, while the middle cerebral artery blood velocity (MCABV) increased on the side contralateral to the carotid surgery (  upper trace ), there was a decrease in MCABV on the ipsilateral side (  lower trace ), indicating a steal phenomenon. For the purpose of this illustration, the pressure and MCABV waveforms have been smoothed with a low-pass filter.