[Assessment of cerebral autoregulation using transcranial Doppler sonography under lower body negative pressure]

A novel technique for transcranial Doppler sonographic assessment of cerebral autoregulation was tried out in 20 healthy volunteers, ten of them right-handed and ten left-handed. A fall in arterial blood pressure was produced through lower body negative pressure (LBNP) of -50 mmHg during 1 min. The Doppler shift signal of both middle cerebral arteries was recorded simultaneously and analyzed digitally to obtain mean Doppler shift frequency and Doppler signal power. Their product, as an index of volume flow, was calculated on-line. By positioning and coupling of the transducers and keeping the position of the head stable throughout the test, spurious readings due to the effects of gravity or head movement were excluded. With an average fall of mean arterial blood pressure of 10.3 +/- 7.7 mmHg, the TCD flow index as averaged over the entire period of LBNP was 103.6 +/- 19.5% of the value measured under atmospheric pressure, demonstrating a physiological autoregulation. In the right-handed subjects the flow index during LBNP was significantly higher on the right than on the left side. In only one of the ten right-handed individuals the side difference was reversed, while this was the case in five of the ten left-handed subjects.