A 45-year-old man with longstanding heavy alcohol use presents confused, with fever, hypotension, tachycardia and a lactate of 5.0 mmol/L. He is suspected to have sepsis from pneumonia. Initial fluid resuscitation and broad-spectrum antibiotics have been given. According to Surviving Sepsis Campaign 2021, if his mean arterial pressure remains below 65 mm Hg after 30 mL/kg crystalloid, what is the recommended first-line vasopressor?