Cerebral hemodynamics during controlled hypotension induced by the continuous infusion of ganglionic blocking agents (hexamethonium, pendiomide and arfonad).

Although the acute cerebral hemodynamic response to blood pressure elevation has been studied in normal man (1), there is very little information regarding the effect upon cerebral hemodynamics of reduction in blood pressure to hypotensive ranges. A moderate reduction in the systemic blood pressure appears to have very little effect on the cerebral circulation (2). However, when the blood pressure is markedly reduced one would anticipate that compensatory vasodilation of the cerebral vessels may be exceeded. Accordingly, the primary purpose of the current study was an estimation of the effect on the cerebral circulation of reduction in blood pressure produced by ganglionic blocking agents. An attempt was made to determine the critical level of reduction in arterial blood pressure beyond which further depression might produce cerebral ischemia and cerebral hypoxia. An estimation of this type is especially indicated because of the current use of controlled hypotension for some surgical procedures. The observations on the cerebral circulation in the current study were made on unanesthetized subjects in whom the blood pressure was reduced by continuous infusion of hexamethonium,2 Pendiomide,8 or Arfonad,4 all of which are ganglionic blocking agents.