Effects of intracranial hypertension on steady and pulsatile haemodynamicsin dogs

1, Intracranial hypertension (ICH) tends to elicit various cardiovascular c hanges, Previous studies on the haemodynamic responses to ICH hare been con fined mainly to measurements of arterial pressure (AP), cardiac output (CO) and total peripheral resistance (TPR), In the present study, we used the t echnique of arterial impedance analysis for a complete assessment of steady and pulsatile haemodynamics in ICR, 2, In anaesthetized dogs, aortic pressure and flow waves mere obtained with high-fidelity Millar sensors. The pressure and flow waves were subjected t o Fourier transformation (frequency analysis) for an analysis of impedance spectra, Intracranial pressure (ICP) was elevated by inflation of an epidur al balloon. At an ICP of 50 mmHg. the changes in steady and pulsatile haemo dynamics were slight, 3, Haemodynamic changes became evident at an ICP of 100 mmHg, The mean. AP was elevated by 31 mmHg (+32%) and heart rate (HR) was reduced by 15 b,p,m, (-18%). There was also a significant decrease in CO by 27% and large incre ase in TPR bg 82%;-,With respect to pulsatile haemodynamics, an elevation o f ICP to 100 mmHg caused significant increases in characteristic impedance by 45% and wave reflection by 53%. Arterial compliance was reduced by 50 %. The ventricular oscillator, work was increased without a significant chang e in steady work, 4. The results indicate that ICH causes constriction of resistance vessels to affect;AP and TPR, Because the pulsatile haemodynamics reflect mainly th e Windkessel functions, ICH also induces stiffness of the large vessels to affect arterial impedance, pulse wave reflection and ventricular oscillator y work.