Changes in mean arterial pressure and end-tidal carbon dioxide content affect venous sinus pressures in patients with idiopathic intracranial hypertension: a randomized study

Introduction Little is known about how changes in physiologic parameters affect venous sinus pressure measurements, waveforms, or gradients associated with sinus stenosis. Objective To evaluate the effect of changes in cardiovascular and respiratory physiologic parameters on venous sinus pressure and caliber measurements in patients with idiopathic intracranial hypertension (IIH) undergoing venous sinus stenting. Methods In a prospective, randomized pilot study, eight patients with IIH undergoing venous sinus stenting were randomized to one of two groups. Under general anesthesia, patients underwent venous manometry and waveform recordings twice in succession based on assigned physiologic groups immediately before stenting. The mean arterial pressure (MAP) group maintained normocapnia but modified MAPs in two arms to control for temporal confounding: group A1 (MAP 60-80 mm Hg then 100-110 mm Hg) and group A2 (MAP 100-110 mm Hg then 60-80 mm Hg). The end-tidal carbon dioxide (EtCO2) group maintained a high-normal MAP similar to standard neuroanesthesia goals and modified EtCO2: group B1 (EtCO(2)24-26 mm Hg then 38-40 mm Hg) and B2 (EtCO(2)28-40 mm Hg then 24-26 mm Hg). Results In group A, superior sagittal sinus (SSS) pressures (ranging from 8 to 76 mm Hg) and trans-stenotic pressure gradients (TSPGs) (ranging from 2 to 67 mm Hg) were seen at MAP of 100-110 mm Hg compared with SSS pressures (4-38 mm Hg) and TSPGs (3-31 mm Hg) at 60-80 mm Hg. In group B, SSS pressures and TSPGs were considerably higher at EtCO(2)levels of 38-40 mm Hg (15-57 mm Hg and 3-44 mm Hg, respectively) than at 24-26 mm Hg (8-26 mm Hg and 1-8 mm Hg, respectively). Conclusions Despite the small sample size, this pilot study demonstrates a dramatic effect of both MAP and EtCO(2)on venous sinus pressures obtained during venography. These findings underscore the importance of maintaining normal physiologic cardiovascular and respiratory parameters during venous sinus manometry.