Therapeutic Handbook - GGC Prescribing

Investigation of Unilateral Pleural EffusionIntroductionPleural effusions, the result of the accumulation of fluid in the pleural space, are a common medicalproblem. They can be caused by several mechanisms including increased permeability of the pleuralmembrane, increased pulmonary capillary pressure, decreased negative intrapleural pressure,decreased oncotic pressure, and obstructed lymphatic flow.Pleural effusions are classified into transudates and exudates:• A transudative pleural effusion occurs when the balance of hydrostatic forces influencing theformation and absorption of pleural fluid is altered to favour pleural fluid accumulation. Thepermeability of the capillaries to proteins is normal. (Common causes – left ventricular failure(LVF), liver cirrhosis, hypoalbuminaemia and peritoneal dialysis).• In contrast, an exudative pleural effusion develops when the pleural surface and/or the localcapillary permeability are altered. (Common causes – malignancy and parapneumonic effusions).Assessment / monitoring• The differential diagnosis of an effusion is wide, and may include pulmonary, pleural orextrapulmonary disease. Please contact local Respiratory team early to guide aspiration andfurther systematic investigation and management (see flow diagram on next page).• According to Light's criteria an effusion is an exudate if any one of the following is true of pleuralfluid aspirate:- Pleural total protein: serum total protein > 0.5- Pleural LDH: serum LDH> 0.6- Pleural LDH > 0.66 upper limit normal range in your hospital.• An accurate drug history should be taken during clinical assessment. Although uncommon, anumber of medications have been reported to cause exudative pleural effusions. Discuss witha respiratory physician or your clinical pharmacist if necessary.• Aspiration should not be performed for bilateral effusions in a clinical setting strongly suggestiveof a pleural transudate, unless there are atypical features or they fail to respond to therapy.Safety and timing of pleural procedures• Current BTS guidance recommends the use of bedside pleural ultrasound at the time ofprocedure where available to guide the site of pleural aspiration and chest drain insertion forpleural effusion. The aim is to reduce complications from perforation of viscera.• Diagnostic / therapeutic aspiration should occur during normal working hours where possible,unless urgently indicated (e.g. large effusion causing significant breathlessness or hypoxia).• Avoid chest drain placement out of hours if possible unless empyema present on diagnostic tap.Removal of all fluid prior to definitive diagnosis may delay further investigations and definitivemanagement, especially of possible malignant effusions.Respiratory SystemContinues on next pagePage 145