A 67-year-old woman comes to the emergency department due to increased dyspnea on exertion. Her chronic medical problems include obesity, obstructive sleep apnea, moderate chronic obstructive pulmonary disease, coronary artery disease, congestive heart failure, hypertension, hyperlipidemia, rheumatoid arthritis, and hypothyroidism. She was treated with antibiotics and a steroid taper for a "lung infection" 1 month ago. Her cough productive of thick yellowish sputum improved, but she has been feeling increasingly dyspneic when walking up stairs and doing her grocery shopping over the past week. She took some extra doses of furosemide with minimal relief.
The patient denies increased orthopnea but says, "I always sleep on 3 pillows so I can avoid using that PAP mask." She has no fever, chills, or night sweats. She smokes half a pack of cigarettes a day. Surgical history is significant for a 3-vessel coronary artery bypass graft 5 years ago.
Her blood pressure is 160/96 mm Hg, pulse is 78/min, and respirations are 20/min. Pulse oximetry shows 96% on room air. Her BMI is 36 kg/m². Physical examination shows mild respiratory distress. Lung examination reveals decreased breath sounds on the right with dullness to percussion almost halfway up. There is 1+ pitting edema up to the knees bilaterally.
Laboratory results are as follows:

Chest x-ray reveals blunting of the costophrenic angle on the left and a moderate right-sided pleural effusion. Thoracentesis is performed on the right and 750 mL of serous fluid is removed. The results of pleural fluid analysis are as follows:

Which of the following is the most likely cause of her pleural effusion?

Question

A 67-year-old woman comes to the emergency department due to increased dyspnea on exertion. Her chronic medical problems include obesity, obstructive sleep apnea, moderate chronic obstructive pulmonary disease, coronary artery disease, congestive heart failure, hypertension, hyperlipidemia, rheumatoid arthritis, and hypothyroidism. She was treated with antibiotics and a steroid taper for a "lung infection" 1 month ago. Her cough productive of thick yellowish sputum improved, but she has been feeling increasingly dyspneic when walking up stairs and doing her grocery shopping over the past week. She took some extra doses of furosemide with minimal relief.
The patient denies increased orthopnea but says, "I always sleep on 3 pillows so I can avoid using that PAP mask." She has no fever, chills, or night sweats. She smokes half a pack of cigarettes a day. Surgical history is significant for a 3-vessel coronary artery bypass graft 5 years ago.
Her blood pressure is 160/96 mm Hg, pulse is 78/min, and respirations are 20/min. Pulse oximetry shows 96% on room air. Her BMI is 36 kg/m². Physical examination shows mild respiratory distress. Lung examination reveals decreased breath sounds on the right with dullness to percussion almost halfway up. There is 1+ pitting edema up to the knees bilaterally.
Laboratory results are as follows:

Chest x-ray reveals blunting of the costophrenic angle on the left and a moderate right-sided pleural effusion. Thoracentesis is performed on the right and 750 mL of serous fluid is removed. The results of pleural fluid analysis are as follows:

Which of the following is the most likely cause of her pleural effusion?

Quizplus · Accepted Answer

11ec193a_969e_0ad9_853d_2704f21c7afb_MD0002_00 The first step in evaluating a pleural effusion is to determine whether the effusion is a transudate or an exudate. Transudative effusions generally do not need further microbiology or cytology studies and are usually due to increased hydrostatic pressure, decreased oncotic pressure, or a combination of both. Exudative effusions are usually due to infectious or inflammatory conditions (Table). Light's criteria classify an effusion as an exudate if >1 of the following are present: Pleural fluid protein to serum protein ratio >0.5Pleural fluid lactate dehydrogenase (LDH) to serum LDH ratio >0.6Pleural fluid LDH level >2/3 upper limit of normal for serum LDH Pleural fluid protein to serum protein ratio >0.5 Pleural fluid lactate dehydrogenase (LDH) to serum LDH ratio >0.6 Pleural fluid LDH level >2/3 upper limit of normal for serum LDH Light's criteria are nearly 100% sensitive but only 83% specific for identifying exudates, and the specificity decreases in the setting of diuretic use. Up to 20% of heart failure patients with pleural effusion may fulfill criteria for exudative effusion after receiving diuretics. In this case, a serum-effusion protein difference >3.1 g/dL or serum-effusion albumin gradient >1.2 g/dL suggests a true transudative effusion. This patient with congestive heart failure on diuretics has worsening dyspnea with bilateral lower extremity edema and a pleural effusion. The effusion meets Light's criteria for an exudative effusion, but in the setting of diuretics, a serum-effusion protein difference of 7.2 - 3.2 = 4 g/dL or a serum-effusion albumin gradient of 3.8 - 1.8 = 2 g/dL classify this as a transudative effusion, most likely due to congestive heart failure. (Choice B) Lung cancer with pleural metastases usually presents with a frankly bloody effusion associated with chest pain. (Choice C) Parapneumonic effusion usually presents closer to the time of the presumed pneumonia with white blood cells (predominantly neutrophils) >1,000/mm³ in the pleural fluid. ³ (Choice D) Pulmonary embolism can present with pleural effusion, especially in patients age <40. However, the effusion is typically small, and there is usually associated pleuritic chest pain and dyspnea disproportionate to the size of the effusion. (Choice E) Rheumatoid pleurisy typically has a very low pleural fluid pH (<7.0) and glucose levels (<30 mg/dL) with very high LDH (>1000 U/L). Educational objective: Light's criteria can distinguish between transudative and exudative pleural effusion. However, a transudative effusion related to congestive heart failure may meet criteria for an exudative effusion after diuresis. Further differentiation may be necessary with either serum-effusion albumin gradient or serum-effusion protein difference. __________ References: Diagnostic approach to pleural effusion in adults. (http://www.ncbi.nlm.nih.gov/pubmed/16623208) The separation of transudates and exudates with particular reference to the protein gradient. (http://www.ncbi.nlm.nih.gov/pubmed/15220755)

A 67-Year-Old Woman Comes to the Emergency Department Due to Increased