Final answer:
The nurse should look for improved skin color as an indicator that the blood transfusion of packed RBCs was effective, as this reflects better oxygenation of tissues.
Step-by-step explanation:
The question asks which of the following findings should indicate to the nurse that the therapy of receiving 2 units of packed RBCs has been effective. The correct answer is b) Improved skin color. This is because the primary function of red blood cells (RBCs) is to carry oxygen to various tissues in the body, and with more RBCs available post-transfusion, one would expect an improvement in the oxygenation of tissues, which can manifest as improved skin color. Improved skin color indicates that the tissues, including those under the skin, are receiving a sufficient supply of oxygen, reflecting the effectiveness of the blood transfusion. The other options, such as increased blood pressure, elevated temperature, and decreased respiratory rate, may not directly reflect the efficacy of a blood transfusion and could be influenced by a variety of other factors.