When sourcing a trolley for portable ultrasound machines, prioritize stability and load-bearing capacity. Ensure the trolley is constructed from medical-grade materials such as aluminum alloy or ABS plastic, which are resistant to chemical disinfectants. Key features should include silent medical casters with independent brakes, a height-adjustable column (gas spring or electric) to accommodate different ergonomic needs, and integrated cable management systems to prevent tripping hazards and maintain a sterile environment.