Ultrasound in anesthesiology in the Nordic countries—Protocol of an international survey on availability, frequency of use, operator training, and certification: Protocol of an international survey on availability, frequency of use, operator training, and certification - Martine S. Nielsen; Anders M. Grejs; Anders B. Nielsen; Lars Konge; Anne C. Brøchner (Acta Anaesthesiologica Scandinavica, 2024)