A 54-year-old man is admitted to ICU with septic shock from a perforated sigmoid diverticulum. He has received 30 mL/kg crystalloid and is on noradrenaline at 0.25 mcg/kg/min. MAP is 58 mmHg, heart rate 120 bpm, CVP 12 mmHg, ScvO2 58%, lactate 5.2 mmol/L, cardiac index 2.0 L/min/m2. Echocardiography shows a hyperdynamic left ventricle with an ejection fraction of 65%. What is the most appropriate next step?