A 54 year old smoker with COPD is admitted with an acute exacerbation and worsening breathlessness. He has already received controlled oxygen, nebulised Salbutamol and Ipratropium, and oral Prednisolone. NEWS2 score remains high with tachycardia, tachypnoea and worsening hypotension. Blood cultures are pending but he has a fever and purulent sputum. According to the Sepsis Six bundle and NICE sepsis guidance, which action should now be prioritised within the first hour?