You received 50 mL of Marcaine 0.25% to the beginning of the case. You have 20 mL left in your medication cup on your back table. How much Marcaine did the surgeon administer to the patient?

To determine how much Marcaine the surgeon administered to the patient, we start with the initial volume received, which is 50 mL of Marcaine at a concentration of 0.25%. From this initial amount, we need to account for what remains. Since there is 20 mL left in the medication cup, we can calculate the volume used by subtracting the remaining volume from the total initial volume.

The calculation is straightforward:

Initial volume - Remaining volume = Volume administered

So,

50 mL (initial) - 20 mL (remaining) = 30 mL (administered)

This means that the surgeon administered 30 mL of Marcaine to the patient. The correct answer is informed by this calculation, clearly indicating that the surgeon used 30 mL of the medication during the procedure. Understanding this process helps illustrate the importance of tracking medication use accurately to ensure safe and responsible administration in a surgical setting.