Answer: B. Reposition the probe every 2 hours.

Rationale:

• A. Warm the skin prior to probe placement: While cold fingers can lead to inaccurate readings, warming the skin is not an essential step and is not routinely recommended in clinical practice.
• B. Reposition the probe every 2 hours: This is correct. Continuous pressure from the probe in one spot can cause skin breakdown and pressure injuries. Repositioning the probe every 2 hours helps to prevent this and ensure accurate readings.
• C. Tape the wire to the palm of the hand: This is incorrect. The pulse oximeter probe should be placed on a vascular site, such as a fingertip or earlobe. Taping the wire to the palm would not provide accurate readings.
• D. Apply the sensor to the index fingernail: This is incorrect. The fingernail does not have sufficient blood flow for accurate pulse oximetry readings. The probe should be placed on the fleshy pad of the fingertip.

Therefore, the most important action for the nurse to take is to reposition the probe every 2 hours to prevent skin breakdown and ensure accurate readings.

Additional Points:

• The nurse should also choose a clean and dry site for probe placement.
• The probe should be snug but not too tight.
• The nurse should monitor the child for signs of skin breakdown, such as redness, swelling, or pain.
• If the child is restless or active, the nurse may need to secure the probe with additional tape or a special wrap.