A 72-year-old man presents with cough, fever and pleuritic chest pain. His observations are: temperature 38.4°C, respiratory rate 32/min, blood pressure 95/60 mmHg, pulse 104 bpm, oxygen saturation 93% on air. Urea is 9.5 mmol/L and he is mildly confused. What is the most appropriate next step in his management?