Final answer:
After administering furosemide, a diuretic, the most important action for the nurse is to measure urine output to assess the effectiveness of the medication and monitor for potential complications.
Step-by-step explanation:
The most important action for the nurse to take after administering furosemide, a diuretic, is to measure urine output. This is because diuretics such as furosemide work by increasing the excretion of water and, importantly, electrolytes such as potassium through the kidneys. Significant changes in urine output can indicate the effectiveness of the medication and also alert the nurse to potential complications, such as dehydration or abnormal electrolyte balance. While auscultating the lungs and reviewing serum potassium are also important, these actions may follow after ensuring that the diuretic is having its intended diuretic effect. Administering albuterol via a nebulizer would be appropriate if the shortness of breath is due to bronchoconstriction, which is not indicated by the data provided.