You are called to a road traffic collision where a 34-year-old motorcyclist has been thrown 15 metres from their bike. On arrival, the patient is unresponsive with a GCS of 6 (E1 V2 M3). There is a large scalp laceration with active bleeding and obvious deformity of the left femur. Heart rate is 128 bpm, blood pressure 78/42 mmHg, and respiratory rate is 28. What is the most appropriate first action in managing this patient?