A 22-year-old university student is brought to the Emergency Department by her friends. She was found unresponsive in her room with an empty packet of paracetamol (32 x 500mg tablets) beside her. It is estimated she took the tablets approximately 6 hours ago. She is now drowsy but rousable (GCS 13/15). What is the most important immediate step in her management after initial ABCDE assessment?