Final answer:
The nurse should first implement the order to start 1000 mL of normal saline at 500 mL/hr when a patient with acute pancreatitis is experiencing hypovolemic shock.
Step-by-step explanation:
When a patient with acute pancreatitis is experiencing hypovolemic shock, the nurse should implement the order to start 1000 mL of normal saline at 500 mL/hr first. Hypovolemic shock is characterized by low blood volume, so the priority is to restore fluid volume and improve perfusion to vital organs. This can be achieved by administering IV fluids such as normal saline.
The other options, including obtaining blood cultures before starting IV antibiotics, drawing blood for hematology and coagulation factors, and administering high-flow oxygen with a non-rebreather mask, are important interventions but should not be implemented before addressing the fluid volume deficit.