ASSESSMENT OF CEREBRAL AUTOREGULATION WITH ULTRASOUND AND LASER-DOPPLER WAVE-FORMS - AN EXPERIMENTAL-STUDY IN ANESTHETIZED RABBITS

THE AIM OF the study was to correlate changes in transcranial Doppler blood flow velocity wave form in the basilar artery with cortical red blood cell flux measured with a laser Doppler flowmeter during hemorrh age-induced hypotension in anesthetized and ventilated New Zealand rab bits. Although systolic flow velocity and flux exhibited an autoregula tory threshold at 45 mm Hg, diastolic flow velocity started to fall wh en mean arterial blood pressure fell below 65 mm Hg. The difference be tween the mean arterial blood pressure at which diastolic blood flow v elocity decreases and the pressure at which mean flux decreases is the difference between systolic and diastolic blood pressure. The increas ing divergence between systolic and diastolic flow velocities was refl ected in an increase in the amplitude of blood flow velocity pulsation s and pulsatility indices. An increase in flux pulsatile wave form was noted as cerebral resistive vessels dilated with hypotension.