A FEEDBACK-CONTROLLED PUMP PRODUCES STABLE HYPOTENSION IN ANESTHETIZED RABBITS

A method is described for the reliable production of controlled hypote nsion in experimental animals. Reduction in arterial blood pressure wa s obtained in rabbits by withdrawing arterial blood using a computer-d riven pump operating within a feedback control system. Arterial blood pressure, blood flow velocity in the basilar artery (measured using tr anscranial Doppler), and anterior cortical microcirculation (measured using laser Doppler) were monitored. The aim of the experiments was to compare stability of hypotension produced using arterial blood pressu re or basilar flow velocity as feedback control variables. Basilar art ery flow velocity provided the most stable profound hypotension and du ring reinfusion when animals were not autoregulating. However, arteria l blood pressure provided the most accurate stepwise control in autore gulating animals.