A 72-year-old male with congestive heart failure is undergoing thoracentesis for a right pleural effusion. Shortly after draining 1.5 L of fluid, the patient develops dyspnea and hypoxia.
What measure, if taken, could reduce the risk of this complication?
A. Limit end-expiratory pleural pressures to less than (−) 20 cm H2OCorrect Answer: A
This patient is likely suffering from re-expansion pulmonary edema (RPE). RPE is a potential complication from thoracentesis for pneumo- or hydrothoraces. The clinical presentation of RPE is characterized by a rapid onset of dyspnea and tachypnea with symptoms most often occurring within 1 hour of the re-expansion of the collapsed lung. Although the exact pathophysiology of RPE is not entirely clear, it is suspected that the mechanism includes the abrupt conclusion of hypoxic pulmonary vasoconstriction, as the alveoli are no longer hypoxic as blood flow returns. There is reperfusion of the lung, bringing in oxygen supply, and there then may be formation of reactive oxygen species. During reperfusion, there are increases in lipid and polypeptide mediators and immune complexes, which lead to damage of the endothelium, which is one way in which pulmonary edema may ensue.
Feller-Kopman et al found that volume of fluid removed was not correlated with development of RPE. Instead, an end-expiratory pleural pressure greater than (−)20 cm H2O was associated with this potential complication. Treatment consists of supportive therapy, with the application of mechanical ventilation and PEEP.
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