Answer: Thanks for your excellent question. The answer depends upon your clinical decision as to whether you believe this patient had acute cardiogenic pulmonary edema (crackles on exam, edema peripherally) or if you felt an alternate diagnosis was more likely (malignant pleural effusion, pneumonia due to obstruction and retained secretions).
Given the malignancy and the past history of “having the fluid drained”, it is entirely possible that this patient was short of breath due to a pleural effusion from the lung cancer. In this situation, the use of nitroglycerin would not be indicated.
If you felt strongly based upon your assessment that this patient was indeed suffering moderate to severe respiratory distress related to acute cardiogenic pulmonary edema, then you would have been supported in following your medical directive for this situation.