The effect of verapamil on cerebral cortical and spinal cord blood flow during proximal descending thoracic aortic occlusion.
The mechanism of central nervous system (CNS) protection during proximal descending thoracic aortic cross-clamping (PDTAC) for aortic surgery using calcium channel blocking agents is not known. In order to determine the effect of verapamil on CNS blood flow during PDTAC, we calculated cerebral cortical (CC), proximal spinal cord (PSC), and distal spinal cord (DSC) blood flow using the microsphere method in Grade I beagles. Flow calculations were obtained at baseline (pre-PDTAC), following mobilization of the proximal descending aorta for 5-8 cm by ligating 3-5 pairs of intercostal arteries (ICA), during PDTAC (45 min), and during maximal reperfusion. Two groups were studied: 1) control (Cont) untreated (n = 5); 2) verapamil (Ver) treated (0.4 mg/kg IV just before PDTAC and just before reperfusion) (n = 5). I) Proximal ICA ligation produces no compromise to SC blood flow. II) Verapamil may protect the CNS by: 1) maintaining cerebral autoregulation during reperfusion; and 2) dampening hyperperfusion of the distal SC during reperfusion.