A pleural effusion is an abnormal collection of fluid in the pleural cavity, the space between the two layers of the pleura (the membranes lining the lungs and chest wall). The normal pleural space contains only a tiny amount of lubricating fluid; when excess fluid accumulates, it can compress the underlying lung, impair its expansion, and cause breathlessness and reduced oxygen levels.
Pleural effusions are classified as transudates (resulting from abnormal fluid dynamics, such as elevated venous pressure in heart failure or low blood protein levels) or exudates (resulting from local inflammation, infection, or malignancy). Common cardiac causes of transudative pleural effusion include heart failure and pericarditis. Symptoms depend on size: small effusions may be asymptomatic, while larger ones cause breathlessness and a dull ache in the affected side.
Diagnosis is confirmed by chest X-ray, ultrasound, or CT scan. Sampling of the fluid (thoracocentesis) may be needed to determine the cause. Examination reveals dullness to percussion and reduced breath sounds over the effusion.
Treatment depends on the underlying cause. Heart failure-related effusions typically improve with diuretic therapy. Infected pleural effusions (empyemas) require drainage and antibiotics. Large symptomatic effusions are drained by thoracocentesis or chest drain insertion. After cardiac arrest, pleural effusions may develop as a consequence of the resuscitation process, heart failure, or complications of intensive care, and are managed as part of the overall post-arrest care.
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