A 62-year-old woman with a history of coronary aery disease presents with a pancreatic head tumor and undergoes a pancreaticoduodenectomy. Postoperatively, she develops a leak from the pancreaticojejunostomy anastomosis and becomes septic. A Swan-Ganz catheter is placed, which demonstrates an increased cardiac output and decreased systemic vascular resistance. She also develops acute renal failure and oliguria. Which of the following is an indication to sta dopamine?