Magnetic resonance imaging of peripheral venous distension with cyclooxygenase inhibition in healthy humans
Authors: Luck J. Carter , Hamaoka Takuto , Sica Christopher , Vesek Jeffrey , Blaha Cheryl , Stavres Jon , Leuenberger Urs , Sinoway Lawrence , Cui Jian 
Published: May 2023

Background: Peripheral venous distension, induced by a volume infusion into the veins in an occluded limb, evokes a reflex pressor and sympathoexcitatory response in humans (venous distension reflex, VDR). However, to what extent the procedure alters the size of superficial and deep veins remains unclear. Our data showed that local cyclooxygenase (COX) inhibition could attenuate the muscle sympathetic nerve activity (MSNA) and blood pressure (BP) responses to venous distension. It is unclear if the COX blockade would alter the magnitudes of the venous distension. The purpose of this study was to evaluate the changes in superficial and deep vein sizes by the venous distension procedure in healthy subjects under local COX blockade and control conditions. This study is associated with a registered clinical trial (NCT03513770). Hypothesis: We hypothesized that the voxel volume of both superficial and deep veins would increase following peripheral venous distension. We further hypothesized that COX blockade would not alter the distribution of infused volume. Methods: The study had a randomized, double-blind, placebo-controlled, and crossover design with two separate visits. Thirteen healthy volunteers underwent peripheral venous distension by which a volume of solution (saline alone or 9 mg ketorolac tromethamine in saline) was infused into the median cubital fossa of an arterially occluded forearm. Each trial (saline or COX blockade) was separated by at least 24 hours. The total infused volume (i.e., 5% of the forearm volume) was held constant across both saline and COX blockade trails. The 3D proton density-weighted magnitude and phase images of the treated arm were obtained before and after the venous distension procedure via a 3T magnetic resonance imaging scanner (Siemens PrismaFit). The average vein voxel volume of 10 forearm veins (six superficial and four deep) was calculated from several adjacent slices of the images. Results: Vein voxel volume was significantly increased by venous distension in both superficial (both P < .001) and deep (both P < 0.01) veins in both trials. However, COX blockade did not influence this increase in voxel volume in either superficial (NSS: Δ2.34 ± 3.05 vs. COX blockade: Δ1.99 ± 2.27 mm3, P = 0.64) or deep (NSS: Δ1.02 ± 1.2 vs. COX blockade: Δ1.06 ± 1.42 mm3, P = 0.94) veins. Conclusion: These data suggest that both superficial and deep veins may contribute to the VDR. Importantly, the results suggest that any attenuation in the MSNA and BP responses to venous distension with COX blockade is not a result of altered magnitudes of the venous distension during the procedure. This study was supported by National Institutes of Health Grants R01 HL144781 (to J.C. and L.I.S). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.