system
Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, METHODS, RESULTS. Meshes: Adult, Carotid Arteries, Cerebral Arteries, Cerebrovascular Circulation, Humans, Middle Aged, Vascular Resistance, Verapamil, Xenon Radioisotopes.
user
Does intracarotid verapamil decrease both proximal and distal human cerebrovascular resistance? Context: The authors determined the segmental effects of intracarotid verapamil in human subjects by using a novel method of measuring proximal and distal cerebrovascular resistance. Their hypothesis was that intracarotid verapamil, a calcium channel-blocking drug that augments cerebral blood flow and reverses arterial spasm, would decrease both the proximal-conductance and the distal-arteriolar resistance. Coaxial catheters were transfemorally floated into internal carotid and middle cerebral arteries during cerebral angiography. Pressures were recorded in the femoral, internal carotid, and middle cerebral arteries. Hemispheric cerebral blood flow was measured by the intracarotid Xe injection technique. Cerebrovascular resistance was measured for the proximal and distal arteries. Cerebral blood flow and hemodynamic data were recorded during intracarotid infusion of saline and verapamil (1 mg/min) for 5 min. Transcranial Doppler blood flow velocity in the middle cerebral artery was also recorded. Intracarotid verapamil increased in 133Xe cerebral blood flow from 43 +/- 11 to 59 +/- 11 ml.100 g(-1).min(-1) (P = 0.001; n = 9). The cerebrovascular resistance measured for the proximal and distal arteries decreased from 0.17 +/- 0.95 to 0.12 +/- 0.75 and from 1.63 +/- 0.78 to 1.03 +/- 0.33 mmHg.ml(-1).100 g(-1).min(-1) (P < 0.01), respectively. The calculated proximal-conductive and distal-arteriolar (pial plus parenchymal) resistances showed a similar decrease. Transcranial Doppler measurements (n = 5) underestimated the effects of intracarotid verapamil that were consistent with an increase in middle cerebral artery diameter.
assistant
Intracarotid verapamil decreases both the proximal-conductance and the distal-arteriolar resistance. Furthermore, it is feasible to investigate segmental effects of drugs in human subjects by measuring changes in pressure gradients within the cerebral arteries and simultaneous Xe cerebral blood flow measurements. Final Decision: yes