<prompt> A 72-year-old man with diabetes, renal insufficiency, and coronary aery disease presents in septic shock from emphysematous cholecystitis. His oxygen saturation is 100 on 6-L nasal cannula and his hemoglobin is 7.2 mgdL. His mixed venous oxygen saturation is 58. Which of the following treatment options will improve his oxygen delivery the most?Increase his inspired oxygen concentrationTransfer him to a hyperbaric chamberAdminister an erythropoietic agentTransfuse two units of packed red blood cells  <response>: Transfusion of 2 units of packed red blood cells will increase the patients oxygen delivery the most. Mixed venous oxygen saturation reflects the difference between the oxygen delivered to the tissues and the oxygen taken up by the tissues. Oxygen delivery is the product of cardiac index and oxygen content of blood CaO2 , the latter of which is determined primarily by hemoglobin Hb concentration. Oxygen saturation SaO2 and the paial pressure of oxygen PaO2 contribute much less. The formula for oxygen content CaO2 can be expressed as CaO21.36HbSaO21000.0031PaO2. Since the patients oxygen saturation is 100, increasing his inspired oxygen concentration is unlikely to increase his oxygen delivery. Since the contribution of PaO2 is so low, hyperbaric oxygen is also not the treatment of choice. Fuhermore, transpoing unstable patients to the hyperbaric chamber can be dangerous. Correction of the patients anemia by the most expeditious manner, that is, transfusion of blood, is the treatment of choice. 