PolyARM Hospital Handbook is a concise, practical guide for multidisciplinary hospital teams managing severely and multiply injured patients from arrival at the emergency department through intensive care and discharge. As the in-hospital companion to the PolyARM Prehospital Handbook, it covers primary and secondary survey, damage-control resuscitation, surgical decision-making, intensive-care management, and the legal and organisational aspects of trauma care. Key points, alerts, action steps, and comparison tables provide rapid access to essential scores, thresholds, doses, and decision rules for bedside use. The handbook is intended for emergency physicians, trauma and orthopaedic surgeons, anaesthesiologists, intensivists, nurses, and trainees, while complementing rather than replacing institutional protocols and local clinical guidance.