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KEY POINTS
Thoracentesis involves the removal of pleural fluid for diagnostic or therapeutic purposes.
The decision to perform thoracentesis should be based on clinical judgment and take into account the perceived safety and utility of the procedure for individual patients.
The use of ultrasound to localize the best site for pleural space access is strongly recommended to reduce complications particularly pneumothorax.
Caution should be exercised in patients with coagulopathy and those receiving mechanical ventilation.
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Pleural effusions occur in 8% to 60% of patients admitted to the intensive care unit (ICU).1,2 Although majority of these patients are in respiratory failure, pleural effusions may not be the primary cause of the respiratory compromise. This is because pleural effusions are mostly secondary to other conditions, such as pneumonia or malignancy. Often the cause of pleural effusion in ICU patients is presumptive based on the overall clinical picture. For these reasons, the decision to perform a diagnostic or therapeutic thoracentesis is often a judgment call. In a questionnaire-based study in France, only 15% of the intensivists routinely performed thoracentesis in ICU patients with pleural effusions, while 37% of the physicians felt routine thoracentesis would result in a specific diagnosis.3 Additionally, there are challenges unique to the ICU, such as mechanical ventilation, multiorgan failure, and coagulopathy. This chapter will address the causes of pleural effusions, technique of thoracentesis including sample handling, special considerations in the ICU patient, and the complications of the procedure.
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PHYSIOLOGIC EFFECTS OF THORACENTESIS IN THE ICU
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In nonventilated patients, regardless of the volume drained, thoracentesis is thought to improve the functional residual capacity (FRC) and total lung capacity (TLC). However, there is no significant improvement in vital capacity (VC), arterial oxygenation, or an improvement in alveolar-arterial (A-a) gradient.4 In mechanically ventilated patients, the physiologic effects of thoracentesis include a decrease in pleural pressure and ventilator work, and a modest decrease in intrinsic positive end-expiratory pressure (PEEPi), but the A-a gradient, arterial oxygen tension (Pao2), and lung compliance do not change significantly after drainage of the pleural effusion.5
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CLINICAL IMPLICATIONS OF PLEURAL EFFUSIONS AND UTILITY OF THORACENTESIS IN THE ICU
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Although pleural effusions are rarely the primary reason for respiratory failure in the ICU, because of their physiologic effects, effusions may contribute to the overall morbidity of ICU patients. In a study of 100 ICU patients by Matheson et al, patients with pleural effusions had longer lengths of ICU stay, and spent more days on mechanical ventilation compared to those without effusions.1 The type of pleural effusion itself seems to have little difference in the clinical outcome. However, Park et al found that patients with transudative effusions needed vasopressor agents more frequently than those with exudative effusions,6 but there was no difference in terms of length ...