A 75 year old man is brought to the emergency department with fever, productive cough, and acute confusion. He is oriented only to person. Blood pressure is 88 over 52 mm Hg, heart rate 120 per min, respiratory rate 30 per min, and oxygen saturation 89 percent on room air. Laboratory tests show lactate 4.0 mmol per L. According to sepsis guidelines, which parameter best defines septic shock in this patient?