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.

This study is a clinical trial designed to investigate the effectiveness of a sacral lift in improving femoral vein size and exposure. If a sacral lift improves femoral vein size and/or exposure, it may improve the success rate of femoral vein cannulation, a critical resuscitative procedure. Femoral vein cannulation can be difficult when the vein is overlapped by the femoral artery. While positioning the leg in abduction with external rotation and knee flexion ("frog-leg" position) is known to improve femoral vein exposure, this study explores the potential added benefit of a sacral lift (a gel pad placed under the sacrum). The study will focus on emergency department patients who frequently require this procedure.

The primary purpose is to determine if the addition of a sacral lift improves femoral vein size and exposure, thereby potentially facilitating easier and more successful cannulation. The study will address the following key questions:

Does the use of a sacral lift significantly increase femoral vein diameter compared to no sacral lift, in both straight leg and frog-leg positions?

Does the use of a sacral lift significantly improve the visualization of the femoral vein (reduce femoral artery overlap) compared to no sacral lift, in both straight leg and frog-leg positions?

The study will employ a comparative design, measuring femoral vein size and assessing the degree of femoral artery overlap with and without a sacral lift, in both straight leg and frog-leg positions. This will allow researchers to directly compare the impact of the sacral lift on these critical factors affecting cannulation success. The findings will provide valuable data for optimizing the technique of femoral vein cannulation and improving outcomes in critically ill patients.

Inclusion Criteria:

• Adult emergency department patients.

Exclusion Criteria:

• <18 or >85 years-old
• Anyone with a history of: deep venous thrombosis (DVT), May-Thurner syndrome, lower extremity vein harvesting, arterial or venous surgery of the lower leg (e.g., peripheral arterial stent placement or sclerotherapy of lower extremity varicose veins), or peripheral vascular disease.
• Anyone with a medical condition that could impact their physical ability to lay supine or abduct and externally rotate their hips safely (e.g., hip fracture).
• Anyone whose femoral vessels cannot be clearly identified using a linear transducer
• Anyone whose femoral vein is not compressible on the study ultrasound (indicating a DVT).
• Vulnerable populations such as pregnant women and those who cannot consent.

It is not necessary for the scope of the study to share IPD.