A 35-year-old male patient is undergoing elective abdominal surgery under general anesthesia. After induction with propofol and fentanyl, succinylcholine 1.5 mg/kg IV is administered for rapid sequence intubation. Five minutes post-intubation, the patient develops severe hyperkalemia (K⁺ 7.2 mEq/L), masseter muscle rigidity, and a core temperature of 38.5°C. The surgeon requests to proceed with surgery. What is the most appropriate immediate next step?