Patient-Controlled Analgesia – Opioid Toxicity in Renal Failure

A 52-year-old male with chronic kidney disease (eGFR 28 mL/min/1.73m²) and poorly controlled diabetes mellitus is admitted for open cholecystectomy. On postoperative day 1, he is prescribed patient-controlled analgesia (PCA) with morphine (demand dose 2 mg, lockout interval 10 minutes, 4-hour limit 30 mg). By 18 hours post-op, he develops confusion, miosis, and shallow breathing (RR 10/min, SpO₂ 88% on room air). Which of the following is the MOST appropriate immediate intervention?