No intracerebral steal phenomenon in the ischemic brain following papaverine administration

The steal phenomenon due to a vasodilator was investigated in 6 cats in which cerebral ischemia had been produced by left middle cerebral artery (MCA) occlusion. The photoelectric method was employed for continuous recording of the cerebral blood volume together with frequent determinations of the cerebral blood flow (CBF) through the ischemic cerebral tissue at the following four stages: before MCA occlusion, 2 hours after MCA occlusion before the injection of papaverine, after the injection of papaverine, and when the systemic arterial blood pressure (SABP) was adjusted non-pharmacologically to the control level using a "vasculator". The administration of the vasodilator produced conflicting results for the CBF changes in the ischemic area with a decrease in SABP as reported previously in the literature. However, when the SABP was corrected to the control level, the CBF in the ischemic region became increased in all 6 cases to above the control ischemic flow values. It is concluded that the decreased CBF in the ischemic tissue after vasodilator administration was not due to the steal phenomenon, but simply to a fall in SABP.