A 35-year-old woman is brought to the hospital 4 hours after ingesting an unknown quantity of antifreeze (ethylene glycol) from a container she mistook for water in her garage in Delhi. She is alert but confused, with a respiratory rate of 26/min and deep breathing. Serum creatinine is 2.8 mg/dL (baseline 0.8), and urinalysis shows calcium oxalate crystals. Arterial blood gas: pH 7.15, HCO₃⁻ 10 mEq/L, PaCO₂ 32 mmHg. What is the immediate next step in management?