Effect of a Sacral Lift on Femoral Vein Size and Exposure

The goal of this clinical trial is to learn if a sacral lift can improve femoral vein size and exposure, which may be clinically helpful during femoral vein cannulation among emergency department patients. The main questions it aims to answer are: Does a sacral lift increase femoral vein size compared to no sacral lift in both straight and frog-leg positions? Does a sacral lift improve femoral vein exposure (reduce overlap by the femoral artery) compared to no sacral lift in both straight and frog-leg positions? Researchers will compare femoral vein size and exposure measurements with and without a sacral lift in both straight and frog-leg leg positions to see if the sacral lift improves vein size and reduces artery overlap. Participants will: Undergo femoral vein ultrasound scans. Maintain a straight leg position with and without a sacral lift. Maintain a frog-leg position with and without a sacral lift.