Final answer:
The nurse could be basing care on Roy's Adaptation Model, which focuses on the patient's ability to adapt to changes in physiological needs and the environment.
Step-by-step explanation:
The nurse could be basing care on Roy's Adaptation Model. This model focuses on the patient's ability to adapt to changes in physiological needs and the environment. By establishing periods of rest and scheduling activities throughout the day, the nurse helps the patient conserve energy and adapt to the low hemoglobin level and fatigue caused by the significant blood loss in surgery.