Final answer:
The assessment finding that warrants immediate intervention by the nurse following a thoracentesis in a client with a large pleural effusion is difficulty breathing.
Step-by-step explanation:
The assessment finding that warrants immediate intervention by the nurse following a thoracentesis in a client with a large pleural effusion is difficulty breathing. This could indicate a complication such as pulmonary edema or pneumothorax, which require immediate medical attention. Other assessment findings that may require intervention include chest pain, hypoxemia, or abnormal sounds heard through a stethoscope.