Final answer:
The nurse should anticipate restoring circulating volume for a postoperative hypotensive patient following abdominal surgery with a blood loss of 400mL. Hypovolemia treatment might include fluid replacement and possibly blood transfusion if necessary.
Step-by-step explanation:
Following abdominal surgery with an estimated blood loss of 400 mL, if a patient is hypotensive postoperatively, the nurse should anticipate interventions aimed at restoring circulating volume. Given that the patient received 300 mL of 0.9% saline during surgery, this may not have been sufficient to compensate for the blood loss. Therefore, fluid replacement is critical to address hypovolemia and to prevent the patient from progressing to hypovolemic shock, a life-threatening condition due to inadequate blood flow and oxygen delivery to tissues.
If the hypotension does not resolve with volume resuscitation, further assessment and interventions, such as checking for internal bleeding or initiating vasopressor therapy, may be necessary. An ECG to check circulatory status may be considered to evaluate for cardiac causes of hypotension, and blood administration may be required if the patient is found to be significantly anemic or continues to lose blood.