 During his tenure at the Vancouver General Hospital, McEwen invented the automatic tourniquet system for surgery.His improvements to tourniquet systems in general led to greater safety and their wider acceptance as the de facto standard for procedures involving bloodless surgical fields and Bier block anaesthesia.For several years, he served on the Board of Governors of the British Columbia Institute of Technology and the (BC) Premier's Advisory Council on Science and Technology, to help advance post-secondary educational programs.