Final answer:
A nurse should monitor a postoperative patient with a heart rate of 111/min and BP of 100/78 for signs of hypovolemic shock, a condition that requires prompt intravenous fluid replacement and possibly medications to stabilize blood pressure.
Step-by-step explanation:
In the early postoperative period for a surgical patient displaying a heart rate of 111 beats/minute and a borderline low blood pressure (BP) of 100/78, a nurse should be most concerned about the possibility of the patient developing hypovolemic shock due to acute intravascular volume loss. Hypovolemic shock is characterized by a rapid heart rate, lower blood pressure, and signs such as cool, clammy skin and rapid, shallow breathing. This condition is typically addressed with intravenous fluid replacement and medications to raise blood pressure. Monitoring for other complications like pulmonary embolism or renal failure may also be prudent, but the immediate concern given the symptoms would likely be hypovolemic shock.