Stable Xenon Does Not Increase Intracranial Pressure in Primates with Freeze-Injury-Induced Intracranial Hypertension

Abstract

Stable xenon (Xe)-enhanced computed tomography is a potentially valuable tool for high resolution, three-dimensional measurement of CBF in patients. However, reports that Xe causes cerebrovascular dilation and increases intracranial pressure (ICP) have tempered enthusiasm for its use. The effects of 5 min of 33% Xe inhalation on ICP (right and left hemispheres) were studied in eight fentanyl-anesthetized Rhesus monkeys after right-sided cortical freeze injury. ICP, CBF, and physiological variables were monitored for up to 6 h postinsult. The preinjury (control) right hemispheric ICP was 8 ± 5 mm Hg (mean ± SD) and left hemispheric ICP was 5 ± 2 mm Hg. Postinjury observations were classified into low (<15 mm Hg) and high ICP (≤ 15 mm Hg) groups. Both right and left ICP values averaged 9 ± 3 mm Hg in the low ICP group. In the high ICP group, the right ICP was 20 ± 4 mm Hg and left ICP was 21 ± 6 mm Hg. ICP was unchanged by Xe inhalation under control conditions as well as in both low and high ICP groups postinjury. Postinjury, the MABP decreased 10–15 mm Hg in the low ICP group and 10–17 mm Hg in the high ICP group 2–3 min after the start of Xe inhalation (p < 0.05). These results show that 33% Xe inhalation does not increase ICP in fentanyl-anesthetized monkeys but could decrease MABP in stressed states, presumably because of the anesthetic effects of Xe.