Effect of flunarizine on canine cerebral cortical blood flow and vascular resistance post cardiac arrest.

Twelve dogs were anesthetized and instrumental for determination of CVP, arterial pressure, intracranial pressure, left atrial pressure, and frontal cerebral cortical blood flow (CCBF) by the thermal method. A catheter was introduced into the venous return of the cerebral confluence to allow determination of cerebral A-V oxygen saturation differences. The animals were placed on cardiac bypass using a circuit from the right atrium to the pulmonary artery and a second circuit from the left ventricular apex to the left femoral artery. A heat exchanger was used to maintain a constant blood temperature of 37 C in the output of the left side bypass circuit. All animals were heparinized during bypass. Ventricular fibrillation was induced after completion of the bypass surgery. Two dogs served as controls. Pre-arrest determinations of hemoglobin, glucose, CCBF, and cerebral A-V oxygen differences were taken. Full circulatory arrest was carried out for 20 minutes by shutting off the cardiac bypass. Resuscitation was achieved by resumption of bypass perfusion. Acid-base balance was corrected quickly, and pre-arrest perfusion pressure was achieved and maintained for 90 minutes. All pressure parameters were monitored continuously. All pre-arrest determinations were repeated at 20, 40, 60, and 90 minutes post resuscitation. Five dogs were treated with 6 microgram/kg flunarizine administered IV drip over 10 minutes immediately post reperfusion. Five dogs were not treated post arrest. Treated animals had a prompt return of CCBF rates equal to or greater than pre-arrest flow, which persisted throughout the period of post-arrest observation. Untreated animals had markedly reduced CCBF and increased resistance. CCBF uniformly proceeded to near zero flow by 90 minutes. The ICP was not significantly altered by treatment.